Swale… Doesn’t it sound elegant to say, “The iris are growing next to the swale?” Well, it certainly sounds classier than saying, “Those flowers, over by the ditch,” but swales and ditches are very similar.

The joy of ditches

​Traditionally, a ditch is a V-shaped or U-shaped channel that is cut next to roads that redirect melted snow water downhill, without flooding the road. When I was a kid in Upstate New York, hammering open rocks in the dried out ditch in front of our house was great fun. You never knew what they were going to look like on the inside until you cracked them open! You couldn’t play in the ditch in spring, though. In spring, the ditch held water that was moving too rapidly to be absorbed and too cold to be any fun.

​Swales are swell

Unlike a ditch, swales are low places that collect water. They can occur naturally or be manmade. You see them all the time next to freeway on-ramps and off-ramps. These particular swales, or contour bands, act as infiltration basins. They are called contour bands because a trench is dug along the natural contour, and then that dug out soil is used to create a berm on the downhill side. Swales collect water that may contain pollutants and filter the toxins out naturally. Since the water in a swale is in a low place, it doesn’t run off. Instead, it is slowly absorbed. Often, ornamental plants that can tolerate pollutants and wet soil are planted around swales. Also, microorganisms in the soil begin breaking those pollutants down into less toxic materials.

Rainwater as resource

We all know that, in nature, rain falls down, is absorbed by the soil, and is then used by plants to grow. Simple. But we have now paved much of that soil. In the United States alone, by 2004, more than 43,000 square miles of land was covered with concrete. That’s about the size of Ohio, and I’m pretty sure that number is higher today. When rain falls on concrete, or other impermeable surfaces, the water runs off and away, carrying topsoil, fertilizers, pollutants, and small bits of trash and plastic with it. We call that run-off urban drool and all of it the ends up in our rivers, lakes, and oceans. The California Native Plant Society tells us that urban drool is the #1 source of ocean pollution. The average 2700 sq. ft. roof in San Jose, California, can collect more than 25,000 gallons of water each year. Rather than allowing that water to go to waste, you can harness it for your garden with a swale.

​Swales in your backyard

​Swales help retain and filter water three ways: slow, spread, sink. First, the flow of water is slowed down because it has a low place to collect. Then, rather than running off, it has a chance to slowly spread and expand through the nearby soil. Finally, the water sinks, naturally, into the soil where it feeds aquifers and underground creeks. All this water attracts the root systems of many of your larger and medium sized trees and shrubs. These nearby plants tap into this resource, which means they need less irrigation water.

Swales as damage reduction

Swales are an effective way to redirect water away from your home, without letting all that water go to waste. Most homes are built with a slightly sloping grade that should take rain water away from your home. This design really helps prevent foundations from shifting, but where does that water go once it’s away from your house? If the slope isn’t steep enough, very often, you will still end up with a muddy yard. Instead, you can redirect water from your downspouts into swales that draw the water away from your house and out into the yard, where it will nurture your plants.

Swales can be beautiful

Swales don’t have to look like a ditch. Instead, they can be made beautiful with river rocks, and plants that can handle the periodic moisture. This would include sedge, mosses, birch, iris, white cedar, azalea, rhododendron, hydrangea, hosta, Peace lily, japonica, ferns, pussywillow, coreopsis, geranium, and scarlet monkey. Heck, if you had a way to filter out the first flush of rain, you might even be able to grow rice! First flush refers to the first 1/2 inch or so of rain that contains higher levels of dust, debris, and pollutants. Before you install any plants, though, make sure that they are not invasive in your area.

Swales can be an attractive part of your landscape. They make the soil healthier, which makes your plants healthier. Plus, there’s less mud in your yard with a swale. Swales can be one part of a rain garden.

Creating areas where rain water can be slowed down and prevented from running off is called  watershed design.

Micronutrients are elements that plants only need in small (micro) doses. These used to be called trace elements, but the American Society of Agronomy and the Soil Science Society of America are urging us to use the term micronutrient instead. Whatever you call them, your plants need them to grow and produce.

Plant nutrition
​
Like us, all plants need water, oxygen, and carbon to live and thrive. They also need the Big Three: nitrogen, phosphorus, and potassium. Beyond that, to function properly, plants need secondary nutrients and micronutrients to stay healthy. All together, these are called essential nutrients. But, before we learn about the various players in the world of plant nutrition, you need to understand that nutrient uptake is a delicate, intricate dance that occurs between root hairs, soil minerals, moisture, soil pH, and some mind-blowing processes, all of which are occurring at the molecular level!

What’s important to keep in mind is that too much of a good thing can be a bad thing. Essential nutrients can reach toxic levels, causing just as much damage as not having enough. To make matters even more confusing, the symptoms of one nutrient’s toxicity make look exactly like a different nutrient’s deficiency. And none of this occurs in isolation. A deficiency in one nutrient can domino into the deficiency of several other nutrients. Also, some plants can  block the entry of some nutrients, preventing toxicity, while others cannot. If that weren’t confusing enough, some nutrient deficiencies and toxicities can look exactly like herbicide overspray damage, pest feeding, or a disease. Fear not! We will sort this out as best we can. Read on!

​Plant nutrients

If you don’t know what your plants need, you can’t give it to them. A basic understanding of plant nutrition can help you help your plants. For a quick refresher of the three macronutrients:
    Nitrogen (N) - used in photosynthesis for rapid leaf growth
    Phosphorus (P) - used in photosynthesis for flower, fruit and root growth
    Potassium (K) - used to fight disease and improve fruit quality

Secondary nutrients also play vital roles in plant health:
    Calcium (Ca) - used for cell wall structure and to move other nutrients around
    Magnesium (Mg) - essential for photosynthesis and it activates plant enzymes
    Sulfur (S) - used to create amino acids for root and seed production

For plants, secondary nutrients and micronutrients work much the way vitamins do for us: you probably won’t die without them, but your teeth may fall out and you certainly won’t be at your best.

Nutrient mobility

As you learn about plant nutrients, you need to know that some of them are free to move around within a plant and others are not. Highly mobile nutrients, such as nitrogen and potassium, go where they are needed. This means that deficiencies are seen in older growth, as the nutrients are pulled away to provide for new growth. The opposite is true for nutrients that do not readily move around. Once they are absorbed, they tend to stay where they are. This means that deficiencies are usually seen in young leaves and new buds.

Below, you will find a brief description of each plant micronutrient. This will help you to understand how these nutrients are used, and what the plants look like if they are missing a nutrient (or have too much).

Aluminum (Al)

Aluminum acidifies the soil by removing hydroxide ions out of water, which leaves acidic hydrogen ions behind. Aluminum is not exactly a plant nutrient, though it is believed to act as a fungicide for some root rots. The reason for its inclusion is that it can be absorbed by plants to the point of toxicity. Aluminum toxicity causes slowed root growth. At the same time, aluminum is frequently applied to tea crops because of the way it prevents copper, manganese, and phosphorus toxicity.

Boron (B)

Boron is used to make cell walls. It also helps plants use and regulate other nutrients by facilitating the production of sugar and carbohydrates. Boron helps plants reproduce. This means plants use boron to flower, fruit, and go to seed. It is also used in pollen generation and cell division. Boron is only available to plants when the soil pH is between 5.0 and 7.5. [My last soil test came back with a pH of 7.7, which is not uncommon in the Bay Area.] Boron is generally created by decomposing organic matter that is deposited on the soil surface. Unfortunately for many of our summer plants, boron cannot be absorbed once the soil is dry. Boron is an immobile nutrient that works in tandem with calcium, so a deficiency of one can lead to the unavailability of the other. Boron deficiency appears as stunted, crinkled, or otherwise distorted fruit or buds (meristem tissue), dark rings on leaf petioles (those tiny stems that attach leaves to twigs), roots that are shorter, thicker, and highly branched, or upper leaves that turn reddish yellow. Too much boron in the soil makes leaves look scorched, with browned areas on leaf tips and edges.

Chlorine (Cl)

Chlorine aids plant metabolism during photosynthesis. It is necessary for osmosis and fluid balance within plants. It is a mobile micronutrient. Too much chlorine in the soil, common in areas with hard water, can interfere with a plant’s ability to absorb nitrogen. [San Jose tap water ranges in pH from 7.0 to 8.7.]

Cobalt (Co)

Cobalt is not needed by all plants. It is only used by legumes in nitrogen fixing.

Copper (Cu)

Copper is used to make reproductive enzymes - that means flowers, fruits, and seeds. Copper also helps plant roots eat and breathe, and it metabolizes proteins. Since copper is not mobile inside the plant, deficiencies are usually seen near the top or in new growth, rather than established leaves and stems. Copper deficiencies can cause leaf rolling and curling.

Iron (Fe)

Iron is essential in the production of chlorophyll and moving electrons around within the plant. Iron is also used in enzyme functions that help your plants absorb many other nutrients. This means your soil, like mine, can contain plenty of everything else, but insufficient iron makes it difficult for plants to get at all that food. Iron deficiencies usually appear as chlorosis (yellowing) and necrosis (dying) between young leaf veins, especially at the top of the plant. Iron is not readily mobile. If your soil is alkaline or deficient in copper, it can make an iron deficiency even worse.

Manganese (Mn)

Manganese is used to make chlorophyll and activates plant enzymes that breakdown carbohydrates and nitrogen into usable bits. It is also used as an antioxidant. Manganese is not mobile, so symptoms of deficiency are usually seen near the top of the plant. Yellowing between the veins of young leaves, with tan flecks, while the areas next to veins stays dark green, is the first symptom of a manganese deficiency. Deficiencies are more likely in alkaline soil. Too much calcium can cause a manganese deficiency, which can, in some cases, be counteracted by adding more nitrogen.

Molybdenum (Mo)

Molybdenum helps plants use nitrogen by working with certain enzymes. If molybdenum is deficient, or if any of those enzymes become sluggish, overall plant growth will slow significantly. Molybdenum is partially mobile.

Nickel

Nickel is used to activate certain enzymes. Insufficient nickel causes a condition called mouse ear, in which stems are shorter than normal and leaves are smaller and more rounded. Insufficient nickel allows urea to collect within plants, causing lesions.

Selenium

Selenium isn’t exactly an essential nutrient, but plants grown on selenium-depleted soils end up being less nutritious for us. Selenium is believed to stimulate plant growth and to counteract stress, pests, and disease. [In the human body, selenium makes antioxidant enzymes that prevent cell damage.]

Silicon

Silicon is found everywhere, so we generally do not think of it as an essential nutrient. That being said, silicon is used by plants to build cell walls and to improve plant health and productivity. Silicon is believed to help plants counteract drought and frost damage.

Sodium

Plants, like us, can suffer or even die from too much sodium, though, for them, it’s not from heart failure. Sodium can replace other critical nutrients within a plant, potassium and nitrogen, in particular. At the same time, low levels of sodium are needed by plants to stimulate growth, maintain a water balance, and improve fruit flavor.

Vanadium

Vanadium is not used by all plants. When it is used, plants are using it as a substitute for molybdenum.

Zinc (Zn)

Zinc helps plants breakdown carbohydrates, and it regulates sugar consumption. Zinc is also used to activate enzymes. It is not mobile. Zinc deficiencies show up as yellowing between young leaf veins and overall bleaching that does not reach leaf edges or midribs. This bleaching can also take the form of narrow yellow or white stripes between the veins of upper leaves. Zinc deficient leaves may also roll or curl, and leaves may be smaller than normal. Zinc deficiencies are common in areas with alkaline soil and/or insufficient organic matter. (So keep composting!)

Mulder’s Chart

Back in 1953, a man named Mulder created a chart that shows how he believed different nutrients interact. The relationships shown in the graph are either antagonistic (red lines) or enhancing (green lines). It takes a little getting used to, and we will discuss it further, but give it a ponder. To get you started, take a look at the lines that point to potash (potassium). You can see green lines connecting it to iron and manganese. That means the presence of potassium, iron and manganese facilitates the uptake of all three, simply because of their chemical makeup.

At the same time, red lines can be seen connecting potassium to boron, calcium, magnesium, nitrogen, and phosphorus. This means that potassium competes with these elements on the root hairs. It also alters soil chemistry, making it so alkaline that iron and boron cannot be absorbed. Of course, there are dozens of other variables at play, so this is an oversimplified explanation of what's happening in your soil, but it might get you to take a closer look at your soil test results!

​What are your plants trying to tell you about the soil they live in?

There’s the toe tappin’, git yer yee-haw on sort of bluegrass, and then there’s one of the most common landscape weeds: annual bluegrass.
Annual bluegrass (Poa annua) is a cool season annual or biennial that appears that appears  each year with the first rains. This weed is a member of the grass family.

The biology of coppicing

​Many trees and shrubs have the ability to put out new shoots, or suckers, from their roots or stump. This can be a royal pain, if you are trying to get rid of a plant. Otherwise, this ability leads to the growth of many thinner, straighter limbs that are well suited to woodworking, basket weaving, wattle and daube fencing, and more. The stump left behind after coppicing is called a stool. Growth rates vary by tree, so a birch tree may be coppiced every 3 or 4 years, for switches, while an oak tree may be coppiced every 50 years, for lumber or firewood.

Did you know that cinnamon trees are coppiced for their bark? What’s really strange about coppiced trees is that they never get old. These plants never leave the juvenile stage. Because of that, the stump, or stool, just keeps getting larger in diameter, but the aboveground growth is always young. Some stools have been coppiced for centuries, reaching a diameter of up to 18 feet! Sometimes, it is decided that coppicing is no longer desired, but a mature tree is. In that case, a single stem is left uncut and all the others are removed. This is called singling. [A copse that has been abandoned to reach full height is said to be overstood.]

Coppicing as woodland management

Traditionally, areas that use coppicing as a management tool do so in sections, called coups. This allows one section to be freshly cut, another to be growing, and yet another to be nearly ready to cut, for a continuous supply of materials. Because of all these various stages of development, copses tend to have a lot of biodiversity. Back in 1544, Henry VIII (yeah, that guy) declared a statute that required coppiced trees be protected from browsers after cutting, and that 12 mature, uncut trees per acre be left in place. These mature trees were called standels. Nowadays, they are called standards. ‘Coppicing with standards’ is still commonly used as a woodland management tool.

Coppicing as permaculture

As long as the soil nutrients are maintained, these trees and shrubs can produce wood indefinitely. This makes them part of modern permaculture. [Permaculture refers to self-sufficient, sustainable agricultural practices.] Small wood harvested by coppicing can be used to create light fencing to keep out marauding hens, to support poles beans and other climbing plants, as building material, and as firewood.

Coppicing as pest and disease management

Coppicing can be used to interrupt common pest and disease triangles. Many insect pests overwinter in cracks in the the bark, at stem and twig joints, or in damaged wood. Diseases often lie dormant in the same places. This infested or infected wood is pruned out, along with the useful harvest.

Coppicing in the garden

Finally! Now that you understand the function, history and usefulness of coppicing, we can see how it is used in the garden. In late winter, before new shoots emerge, you can coppice a variety of trees or shrubs in your garden or landscape. Of course, this only works on plants that can handle heavy pruning. To coppice, simply cut off at or near ground level, while the plant is dormant.

In addition to willow and hazelnut, alder, ash, birch, dogwood, elm, hornbeam, oak, and sycamore handle coppicing well. Most of these are broad-leafed hardwoods. Most conifers should not be coppiced, yew being the exception. There are several reasons for coppicing in the garden or home landscape:

• Maintain smaller tree and shrub sizes
• Sustainable firewood, fencing, and other building materials
• Encourage trees and shrubs with brightly colored new growth
• Regenerate overgrown shrubs
• Convert a single-trunked tree into a multi-stemmed shrub
• Generate income by selling the fresh cuttings to florists

Trees with a trunk diameter greater than 6 inches may not respond well to coppicing. That’s alright because amateurs shouldn’t be trimming big trees, anyway. It’s dangerous. Seriously.
Coppicing can reduce problems associated with too much shade, clogged rain gutters, and shifting foundations. When the upper portion of a tree of shrub is coppiced, some of the underground roots die back. In spring, new roots emerge.

Shrubs that can be coppiced include:​

Damage caused by medflies

Medflies lay their eggs in the skins of over 250 different fruit, nut, and vegetable crops. When the eggs hatch three days later, the maggots burrow into what we normally eat, making it inedible. Once maggots have eaten their fill, either the rotting fruit falls, or they drop to the ground where they pupate in the soil. In one week, an adult emerges and the whole cycle begins again.

Crops affected by the medfly

It would probably be easier to list the crops not affected by medflies, but this should give you an idea: apples, apricots, avocados, cherries, figs, grapes, grapefruit, lemons, limes, melons, nectarines, oranges, peaches, pears, persimmons, plums, pomegranates, sweet peppers, tangerines, tomatoes, and walnut.

The ripple effect

Like most things in life, this situation is not limited to bug-infested food plants. Commercial and home growers will end up using more pesticides to counteract this insect, which can lead to more ground water contamination and chemical resistant pests. Also, areas with medfly populations are unable to sell their produce, infested or not, to other states and other countries. Finally, native plants that produce fruit or nuts can also be attacked by this pest.

Medfly controls

The first appearance of a medfly in California took place in 1975. I remember hearing about it in the news - everyone was talking about it. The government declared a “state of emergency” and 100 square miles were placed under quarantine, and 600 million sterile male medflies were released to interrupt breeding. Malathion was sprayed all over the place. It cost $1 million and took a year, but the medfly was eradicated. For a time.

When the medfly returned in 1981, Governor Brown delayed aerial spraying of malathion, claiming environmental concerns. That was when we learned that medflies reproduce and feed at astounding rates. In that case, the medflies needed only one month to destroy millions of dollars of crops, and to threaten billions more, over an area of 530 square miles. When it was realized just how devastating this pest could be, the California National Guard was called upon to create highway checkpoints to confiscate infested produce.

Now, when a single medfly is spotted, it is checked for gender and fertility, and then all the stops are pulled: aerial spraying, ground spraying, trapping, irradiation, releasing sterile male medflies, public information, and quarantines.
​
What can you do?

First, never, ever, EVER smuggle fresh produce, plants, or soil from infested areas into uninfested areas. Do not mail fresh produce into uninfested areas either.

The USDA Animal and Plant Health Inspection Service provides up-to-date records of current sightings and quarantines, and instructions for reporting any sightings.

Chicory is a woody perennial that comes in many different varieties, depending on the cultivated use: roots (var. sativum) and leaves (var. foliosum) are the most common. Chicory, occurring naturally, can indicate compacted soil. Luckily, its deep taproot helps break up that compacted soil, plus it’s a drought tolerant plant!

​Chicory’s bitter truth

It’s true. Chicory has a bitter taste. Some people like it and some don’t. Science Daily published an interesting report about the evolution of bitter taste sensitivity. It talks about how we evolved to dislike bitterness to avoid being poisoned but, as a result, we now avoid many healthy foods! It’s an interesting read; check it out.

​Chicory as food

Chicory is a highly versatile plant. It’s slightly bitter leaves are used in salads, the buds can be blanched in boiling water, and the taproots are frequently roasted and ground up as a coffee substitute. Chicory is also grown as livestock feed and is said to combat internal parasites. The leaves of wild chicory and domesticated chicory plants that have been stressed are more bitter than domesticated varieties. You can reduce the bitterness by changing the cooking water 2 or 3 times. If you want to harvest chicory root for a Big Easy beverage, gather them before the flowering stems emerge. These roots can also be cooked and eaten the same as carrots or parsnips. Chicory roots can also be ground into flour and used to make bread, and some brewers add chicory to their beer recipes. How’s that for versatile?

Chicory and nutrition

We’ve all heard how important it is to eat our fruits and vegetables. And a certain sailor has been telling us, for decades, to eat our spinach. You may be surprised to learn that chicory contains powerful disease-fighting compounds called polyphenols. In 2013, the Journal of Nutrition published research that showed adults who consume 650 mg of polyphenols each day tend to live longer and better than those who don’t. This is due to polyphenols’ abilities to protect your cardiovascular system, fight cancer, and reduce inflammation. One cup of chicory contains 235 mg of polyphenols, which is twice the amount found in spinach!

Chicory’s family tree

Family trees can be funny things. It’s like going to a reunion and learning that you are actually related to that person. A member of the sunflower family (Asteraceae), chicory (Cichorium intybus) is one of those large, gregarious groups that keeps turning up in unexpected places, and some of the connections aren’t exactly clear. For example, curly endive, Belgian endive, and radicchio are all types of chicory, dandelions and lettuce are siblings, and chicory’s cousins include sunflowers, artichokes, yarrow, chrysanthemums, and even dahlias.

Chicory description

Chicory’s pretty blue flowers have lent it many names: cornflower, bachelor’s buttons, coffeeweed, blue daisy, and wild endive. Like other members of the sunflower family, the flowers are composite and leaves are normally toothed or lobed. The tough, hairy flowering stem is grooved and plants grow 10 to 40 inches tall. Occasionally, the flowers can be white or pink, but this is rare. Flowers appear July through October. Like dandelions, chicory plants have an irritating milky sap that you know as latex.

Chicory leaf types

Many people call leaf chicory ‘endive’, but this is a mistake. True endive (Cichorium endiva) is its own species. The two can, however, cross-pollinate and hybridize, but that only affects the seeds produced that year. There are three types of cultivated leaf chicory (Cichorium intybus):

• Belgian endive [pronounced on-DEEV]— small heads of white (etiolated*) endive
• Radicchio - softball sized head with red or red and green variegated leaves
• Sugarloaf - looks like Romaine lettuce, but toothed and with more bitterness

*Sometimes, chicory receives a special treatment called etiolation. In the culinary world, this is called blanching. [The word ‘blanching' can also refer to a cooking method that submerges food briefly in boiling water, but I digress.] Whatever you call it, this refers to blocking sunlight to all or part of a plant to produce longer stalks (celery), or white leaves (Belgian endive).

How to grow chicory

In warmer climates, chicory is a cool season crop that can be started in January and February, for an early summer crop, and again in July or August, for an early winter crop. This gives the seeds time to get started before the weather turns too hot or too cold. Chicory grown in areas with scorching summers tends to bolt, and the leaves are more bitter. A light frost actually reduces some of the bitterness and adds just a touch of sweetness. Seeds should be planted 1/4 inch deep and thinned to 12 inches apart. Avoid overhead watering, as the leaves are prone to rotting.

Chicory pests and diseases
​
Despite its rugged nature, there are some pests and diseases that can impact chicory. Bacterial soft rot, damping off disease, fusarium wilt, white mold, anthracnose, bottom rot, downy mildews, and septoria blight are all diseases that attack chicory. Aphids, cabbage loopers, darkling beetles, flea beetles, leaf miners, thrips, and slugs and snails may feed on your chicory plants.

Chicory is one of those plants that can grow like a weed. Once established, you can pretty much ignore it until you decide to harvest whatever part you have a hankering for. And, hey, even the flowers are edible!

Cold frame design

You can certainly buy cold frame kits, but this innovation is easy to make for yourself. There are tons of free online instructions and designs available. [Personally, I enjoy the variety found at Instructables.] The next time you see someone getting their windows replaced, grab the old one(s). These old windows act as the roof to your cold frame. All you have to do is build a 2-foot tall frame for the sides. Just be sure to use wood that is rot resistant, such as redwood or cedar, and that it does not contain any toxic chemicals, paint, or stain.

Ideally, your frame will tilt the glass toward the winter sun, allowing the space to collect as much heat and light as possible. You will want to make sure that the angled roof directs rain away from your home’s foundation, if that is where you put your cold frame. If you do not have access to old windows, you can also use plastic sheeting, clear plastic panels, or row cover material. When building a cold frame, be sure that you can prop the cover up, or remove it, during warmer weather, or you may cook your plants.

Crops suited to cold frames

Being relatively low to the ground, cold frames are suited to low-growing, cool season crops. This includes lettuce, spinach, scallions, radishes, turnips, rutabagas, parsley, cilantro, chard, beets, and daikon, just to name a few. You certainly won’t bring sunflowers to harvest in a cold frame, but you can use one to nurture their seedlings, giving them an early start.

Cold frames and dormancy

Unless you have a greenhouse, or bring them indoors, some tender perennials simply do not look their best during the winter months. Some may not be able to survive at all. You can use a cold frame to protect these plants from harsh winter weather. They will still go dormant, but it will be a gentle dormancy, rather than a life threatening struggle to survive. This makes them better able to thrive when spring arrives. To overwinter dormant plants in a cold frame, use these steps:

1. Cut the plant back as much as possible, depending on the species, before the first frost.
2. If the plants are not already in containers, dig them up and put them in pots.
3. Fill the cold frame with potted plants, stuffing the spaces between pots with mulch, straw, soil, or dry leaves.
4. Top the pots with mulch.
5. Water well, at first, then taper off as temperatures drop.

Heat management in cold frames

The whole point of a cold frame is to protect plants from weather they might not otherwise be able to handle, especially damage from frost. However, problems can arise when a warm day occurs in the middle of winter. This can trigger plants into thinking it is time to start growing again, even if it’s January. On days when temperatures are 35°F to 45°F, open the cold frame part way. If temperatures reach 45°F to 50°F, open it completely. [Just be sure to close it again before you go to bed!]

Seedling support

Just as cool weather crops can be grown deeper into winter, seedlings can get as much as a 6 week head start when started indoors or in a greenhouse, and then hardened off in a cold frame. Seedlings can be planted directly in the soil and protected with a portable cold frame, or potted seedlings can be held in a permanent cold frame until they are strong enough (and temperatures outside are warm enough) to be given their place in the soil. Seeds will need to be watered regularly. Once they germinate, be sure to vent the cold frame frequently to avoid damping off disease of seedlings.

Most pests are kept out of a well-designed cold frame. The same characteristics will also prevent pollinators from doing what they do, so don’t expect to be able to grow melons or squash in your cold frame unless you hand-pollinate the flowers.

Robber fly description
​
There are over 7,500 different species of robber fly, ranging in size from 0.2 inches up to 2 inches long. All of them are sturdy, bristled flies with a distinct mustache, made of of bristles (setae), called a mystax. Robber flies, like many other insects, have three simple eyes (ocelli), in a depression on top of their head, between two very large compound eyes. [Simple eyes, like ours, have only one lens, while compound eyes have many lenses.] Robber flies generally have robust legs with spines, and short, segmented antennae. Most species of robber fly have long, skinny bodies with stinger-like ovipositors, while others look more like bumblebees. Robber flies will inflict a painful bite with their proboscis (tubular mouth part), if they feel threatened.

Robber fly life cycle

There is surprisingly little known about the private lives of robber flies. They seem to prefer dry, sunny, open environments. Each robber fly can live for up to 3 years. Eggs can be translucent (hyaline) or pigmented, spherical or oval, depending on the species. Yellowish or white larvae, with tapered bodies and a dark head, are believed to live in leaf mold, rotting wood, and in the soil. There are four larval stages, or instars. Scientists are only now learning about the feeding behavior of robber fly larvae. It’s pretty strange. For one thing, the first instar does not eat insects; it probably eats dead things. The second instar eats beetle larva secretions. [Don't ask.] Later instars are actual predators. Robber fly pupa are naked and have leg stubs, so they can move around, similar to hornworm larvae.

Robber fly prey

Robber flies are generalists. That means they will chase after and kill pretty much anything that flies by, beneficial or not. That is why I said, for better or worse.” Robber flies will kill many garden pests, but they will also kill beneficial insects. Some of these prey insects are pretty substantial in size, compared to a robber fly. But, adult robber flies are excellent fliers. You can usually hear them coming, but for their prey, it’s already too late. Hiding in ambush, a robber fly spots its target, gives chase, and grabs ahold with its tarsi (front legs) before injecting a chemical cocktail that paralyzes the prey and liquifies its insides. The most common victims of robber fly attack include:

• ants, bees, wasps, sawflies (Hymenoptera)
• butterflies, moths (Lepidoptera)
• beetles (Coleoptera)
• flies, crane flies, horseflies (Diptera)
• grasshoppers, crickets, katydids (Orthoptera)
• leafhoppers, stinkbugs, aphids (Hemiptera)

They have also been recorded feeding on:

• dragonflies, damselflies (Odonata)
• lacewings, antlions (Neuroptera)
• spiders (Arachnida)
• termites, cockroaches (Blattodea)
• thrips (Thysanoptera)

And, hummingbirds. It’s rare, but it has happened. You can see some excellent video of robber fly behavior at Mike Blair Outdoors.

Have you seen any robber flies in your garden? Do you consider them to be Good Guys or Bad Guys?

If you grow Brussels sprouts, you are in good company. Brussels sprouts look like an impressive Medieval weapon and taste far sweeter than the frozen, store-bought variety. [Show up at Grandma’s house on Thanksgiving with a freshly cut stalk of Brussels sprouts, and I can guarantee you will be the talk of the day!]

Black blight symptoms

Impressive and delicious, your Brussels sprouts plant may develop light brown or black leaf spots, often with a yellow halo. These spots usually stop at leaf veins and can have an angular shape. These leaf spots are fungal population explosions. In severe cases, these lesions can also occur on the sprouts. Over time, they begin to look more like the concentric rings of a target. If you look closely, with a hand lens or microscope, you can see the fruiting structures. Complete leaf loss can occur.

Black blight life cycle

Since infected leaves fall anyway, take them off and throw them in the trash. The pathogen that causes black blight, Mycosphaerella brassicicola, is in the soil. It also travels on the wind and via splashing rain. It prefers cool temperatures and moist conditions common in autumn - just as your Brussels sprouts are growing.

Black blight control
 
Since the pathogen is probably in your soil, the best control measure is to plant resistant varieties. Also, monitor plants for signs of black blight. Infected plants, or plant parts, should not be added to compost. If black blight has occurred in your garden, try a 2- to 3-year crop rotation and remove weeds that may host the disease.

Fruit fly description

There are actually thousands of different fruit fly species around the world. Most of them are less than 0.12 inches long, brown or yellow, with red eyes. The legless maggots are yellowish-white, only 0.2 inches long, and some species have pointed ends. Pupae are oblong with a forked breathing tube at one end. Some insects, such as Malaysian fruit flies (Bactrocera latifrons) are actually blowflies, and not true fruit flies. There are two major families of fruit fly: Drosophila and Tephritidae. 

​Drosophila flies

Because of their short lifecycle and profound reproduction rates, Drosophila, also known as vinegar flies or common fruit flies, are very popular in genetic research laboratories. The common fruit fly genome is well documented, with only four pairs of chromosomes. Two common species are D. melanogaster and D. simulans. Only one of the common fruit fly’s claims to fame includes the fact that their sperm cells are 2.4 inches long, which is 20 time longer than the fly, and 1,000 times longer than human sperm cells. I don’t know how they do it.

Tephritidae flies
​
Tephritidae flies are sometimes referred to as peacock flies, due to their colorful markings. These markings often mimic other, actually dangerous insects. This copy-cat behavior is called Batesian mimicry, in case you were curious. There are over 5,000 species within this family, including apple maggots, western cherry fruit flies, walnut husk flies, and the dreaded Mediterranean fruit fly (Ceratitis capitata), or medfly. Unlike common fruit flies, members of this group lay eggs in leaves, stems, flowers, seeds, and roots, as well as in fruit. One member of this family, Euphranta toxoneura, deposits eggs in galls created by sawflies.

​Fruit fly damage

As fruit fly larva feed on ripe fruit, they leave a trail of frass (bug poop). They also create points of entry for yeasts that cause souring, along with other pests and diseases. Fruit flies on grapes (Drosophila spp.) can lead the way to bunch rot spreading throughout your vines. The olive fruit fly (T. Bactrocera oleae), considered the world’s worst olive pest, has been known to destroy entire crops. 

​One species of fruit fly, D. suzuki, also called spotted wing drosophila, has a taste for soft fruits, such as raspberry, strawberry, blackberry, cherry, and blueberry. There is not enough information available at this time to determine what sort of an impact these pests will have on those crops, but it doesn’t look good.

Fruit fly controls

Outside of your kitchen, fruit flies are prey to robber flies, yellowjackets, ants, and certain beetles. Since ripe fruit is what attracts fruit flies in the first place, regularly harvesting fruit crops, such as tomatoes, melons, squash, grapes, and olives before they become overripe, can reduce fruit fly populations. Be sure to throw out the mummies, while you’re at it. Overripe potatoes and onions can also attract fruit flies. So can sink drains, mops, garbage disposals, trash cans, cleaning rags, recycling bins, and empty bottles. All fruit flies need is warmth, moisture, and something fermentable to eat. Eliminating any one of those three conditions can break the fruit fly triangle. Insecticides are not effective as long term controls, but pheromone traps can be used to interrupt fruit fly mating.

You can make your own fruit fly trap with a glass and a funnel. Simply place a piece of overripe fruit, some yeast and water, or cider vinegar, beer, or wine in the bottom of the jar and place the funnel on top, similar to a green fruit beetle trap. [Do not use apple cider flavored distilled vinegar - we may be fooled but fruit flies are not.] Fruit flies will be attracted to the bait and find their way in, but will be unable, for the most part, to find their way out. [If your funnel has spacers on the outside edges for air flow, cover the space with tape.] Every few days, take your trap apart and wash it with soap and water, before adding new bait. Within a couple of weeks, your fruit fly problem should be gone. Just be sure that you do not throw the contents of your trap in the trash, as it will contain hundreds of fruit fly eggs just waiting to hatch! Use soap and hot water to wash the glass and funnel. Let the hot, soapy water flow into the drain for at least one minute to wash any fruit fly breeding grounds out of your pipes.

As for those bananas you bought at the grocery store - rinse them off as soon as you get home. This will help to dislodge any fruit fly eggs before they can hatch. And refrigerating produce will halt the development of any fruit flies that remain.

Phosphorus is an essential plant nutrient, second only to nitrogen in plant health. In fact, phosphorus is found within every living cell on earth. It is part of our DNA and every cell wall.

Phosphorus helps plants use and store energy. It is also used make oils, sugars, and starches, within each plant. Most important to the home gardener, phosphorus supports flower and root growth. Much the way nitrogen supports vegetative growth, and potassium supports crop quality and size, phosphorus is the reproduction nutrient, the in-between stage between growing and fruiting. It supports root, flower, seed, and fruit growth. Phosphorus is also part of photosynthesis.

Sources of phosphorus

Despite being so important, phosphorus is rarely found in a form plants can use. This is because phosphorus is highly reactive. When elemental phosphorus is exposed to oxygen, it actually glows! [This is where we get the word ‘phosphorescence’!] Mostly, phosphorus exists as an acid- or salt-version of its former self, called phosphates. Scientists recently discovered that phosphorus is created when a star goes supernova. Here on Earth, organic sources of phosphorus include animal manure, urine, guano, compost. blood meal, and bone meal. Most of the phosphorus found in bags of fertilizer is mined in China, Russia, and the midwest, with 50% of the world’s supply found within the borders of Arab nations. [Perhaps phosphorus will become the new petrol...] Phosphorus is commonly applied around seeds at planting time in a process called banding.

Worldwide, the demand for phosphorus is growing twice the rate as the human population, mostly for agricultural use as fertilizers and pesticides. Phosphates are also used as nerve agents and in detergents. [I prefer soap nuts.] Experts predict a phosphorus shortage by 2040, and a complete end of mineable phosphorus in 345 years. Other experts claim this will happen much sooner. Yet another reason for not applying fertilizers your soil does not need.

So, before we run out, how do you know if your plants have enough (or too much) phosphorus?

Nutrient mobility

Phosphorus is a mobile nutrient, which means that it can be moved around, within a plant, after it has been absorbed. Other nutrients, such as iron and calcium, are described as ‘immobile’ because they generally stay where they were first dropped off by the vascular system. The reason this matters is that it helps in identifying deficiencies and toxicities. Mobile nutrient deficiencies are normally seen in older leaves first. This is because mobile nutrients are pulled out of older leaves to provide support for new leaves. With immobile nutrients, the opposite is true. Older leaves have already gotten their nutrients and hold them in place. The new leaves do not have access and so exhibit deficiency symptoms.

Phosphorus deficiency and toxicity

Phosphorus deficiency is practically unheard of in California home gardens. The optimal range, in parts per million, is 4 to 14. My soil test results reported a value of 84.3 - nearly 10 times what my plants need! The problem wasn’t phosphorus deficiency, but accessibility. Without enough iron in the soil, my plants could not access all that phosphorus (and several other important nutrients). In addition to being rare, phosphorus deficiency can be difficult to identify. In the early stages of growth, a deficiency may appear as nothing more than sluggish growth or mild stunting.

​Since phosphorus is an important part of genetic information transfer, deficiencies ultimately result in smaller and fewer leaves, and fruit set failure. This deficiency also causes a procedural imbalance between photosynthesis (carbohydrate production) and carbohydrate storage. This imbalance leads to too many carbs in the leaves, which makes them darker and more purple or red than normal, especially on the underside, with a shiny almost metallic appearance on the top surface. These symptoms cannot be relied upon as a diagnostic tool, because the same symptoms may indicate several other conditions. Soil testing and plant material testing are the only way to know for sure.

Too much phosphorus can interfere with a plant’s ability to absorb copper and zinc, but this condition is extremely rare in garden environments. It can be seen in containerized plants, or those being grown hydroponically. Zinc and copper deficiencies appear as chlorosis, twig dieback, and bronzing.

Testing for phosphorus

Soil tests are invaluable in learning about what is in your soil. The reason for using a local reputable lab lies mostly in the tests for phosphorus. There are two tests generally used when calculating phosphorus levels: the Bray P1 test and the Olsen sodium bicarbonate test. Their effectiveness lies in soil pH. The land west of the Rockies tends to have alkaline soil, which is better suited to the Olsen test. More acidic midwest and eastern seaboard soils give a more accurate reading when the Bray test is used. If you send your soil samples to the other side of the country, your results may be less accurate (and less useful).

So, before you add any more phosphorus to your soil, take the time to find out if it is actually needed.

Finally, did you know that the rough surface used to strike a match is made with glue, ground up glass, and phosphorus? Now you know.

Horses and cows love it, but what is alfalfa? Is it the same thing as hay? What about straw? Let’s find out!

To start, hay refers to any member of the grass or legume families that have been mown and dried as fodder, or animal feed. You can find oat hay, wheat hay, ryegrass hay, clover hay, timothy hay, alfalfa hay, and others. Straw, or stover, refers to the dried stalks leftover after harvesting grains, such as oats and rye. Straw is generally used as bedding, though it can be used as a low quality feed. Alfalfa stover makes a good bedding for rabbits, guinea pigs, and hens.

Alfalfa is a legume, like peas and beans, but it grows more like oats or barley. Native to southwestern Asia, alfalfa is primarily grown as fodder for livestock. It is either dried and baled, or fermented as silage. Many gardeners are finding that alfalfa’s deep roots and nitrogen-fixing ability make it an excellent cover crop or green manure.

Alfalfa history

Alfalfa (Medicago sativa) is a flowering perennial in the pea family. Alfalfa was first farmed, over 6,000 years ago, in Iran. Then the Persians took this valuable crop to Greece around 500 BC. The Latin name, Medicago, refers to the ancient people of Iran, the Medes. The Arabic word for this crop, al-fiṣfiṣa, is what gives us our common American name for it. The rest of the world has been calling it lucerne, but that is slowly changing as more  of the world’s alfalfa crop is grown in California.

The alfalfa plant

As a perennial, alfalfa plants grow for an average of 4 to 8 years, though they can live for 20 years. These deep-rooted plants, while only 3 feet tall, can reach down as much as 49 feet to find water! I guess it’s safe to assume that they are drought tolerant. In fact, alfalfa is rated as drought-resistant, meaning it can go for long periods of time without any water at all. Most of the time, alfalfa roots only go 6 to 9 feet deep, which is still pretty impressive, when most annual vegetables only root 6 to 12 inches down. Once established, alfalfa plants create a sturdy crown at ground level. Much like sorghum, these crowns contain bud shoots that make it possible to harvest a crop only to have a new one grow.

​Alfalfa is usually mown 3 or 4 times a year, but it can done up to 12 times a year, in an ideal microclimate. Overgrazing, or over-harvesting, can damage the crown. After flowering, pollinated flowers produce spiraled fruits that contain 10 to 20 seeds. Alfalfa plants uses chemicals to prevent other alfalfa plants from growing nearby. This is called autotoxicity. It is triggered after the first seeding of an alfalfa plant and it continues for the remainder of that plant’s life. because of this, crop rotation with corn, wheat, or other crops must be used before replanting an area with more alfalfa.

Nutrients in alfalfa

Alfalfa is a highly nutritious plant. It contains high levels of protein, fiber, and carotenoids. Alfalfa is highly combustible and it can cause bloating when eaten fresh, by livestock, so it is normally dried first. Alfalfa, like other legumes, also has root nodules that contain beneficial bacteria, Sinorhizobium meliloti, that are able to convert atmospheric nitrogen into a form usable by plants. You can buy alfalfa meal, as a nitrogen source, or you can grow your own.

How to grow alfalfa

Alfalfa, like wheat, can be sown in either spring or autumn. These plants need a neutral soil pH of 6.8 to 7.5 to thrive. Other factors are less important. Alfalfa uses a lot of phosphorus and potassium, but our Bay Area soil tends to have both in abundance. (See Soil Test) Alfalfa seeds are planted 1/2 inch deep and should be spaced at 6-inch intervals. When farmers plant alfalfa, they use a machine, called a drill, that inserts a single seed at the right depth and spacing, as the farmer drives over a field. Since alfalfa is sensitive to weed competition in its early development, the proper spacing is rather important.

If you are growing your own alfalfa for the first time, use 1/4 pound of seed over a 25 square foot area (or 20 pounds of seed per acre). Planting it will take some time, because these seeds are really tiny, so put on some music and wear a hat. Alfalfa does not grow well on slopes or in areas with shallow soil. [Raw, unsprouted alfalfa seeds contain chemicals that can be toxic to humans, causing lupus-like symptoms, so don’t eat them. Also, there is no scientific research to verify medical claims made about alfalfa or its sprouts. Leave alfalfa to your soil and the livestock, where it belongs.]

Alfalfa pests and diseases

Blister beetles,  thrips, spider mites, weevils, armyworms, nematodes, cutworms, grasshoppers and crickets, leafhoppers, and aphids are all attracted to alfalfa. Alfalfa is prone to several root rots, such as rhizoctonia, phytophthora, and Texas root rot. Other alfalfa diseases include fusarium wilt, downy mildews, anthracnose, bacterial wilt, and verticillium wilt. Since alfalfa, along with clover, rye, and other legumes can host bean mosaic, it is a good idea to keep some distance between them and your bean crops. Also, voles, pocket gophers, and ground squirrels can be major alfalfa pests.

Alfalfa as insectary and habitat

Insectaries are plants that attract and provide for insects. Alfalfa’s purple flowers are a big favorite of honey bees and other pollinators. Commercially, alfalfa and cotton are intercropped because of predatory insects attracted to alfalfa help to protect the cotton crop. Alfalfa also provides food and habitat to over 130 bird species and many other forms of wildlife. Alfalfa flowers are responsible for the majority of the honey produced in the United States. That being said, it ends up that bees and alfalfa don’t necessarily play well together. The structure of an alfalfa flower makes it so that a western honey bee gets knocked in the head each time they land on a flower. Apparently, bees don’t like getting knocked in the head, so they sip alfalfa nectar from the side of the flower, foregoing the pollen transfer. Since it takes young bees a few knocks to the noggin to learn this trick, pollination still occurs, but only because beekeepers make sure there are plenty of inexperienced bees in the hive when they service alfalfa fields. Alfalfa leaf cutter bees do a much better job of pollinating alfalfa than honey bees.

Even if you only have a driveway or fence strip, try your hand at planting some alfalfa. It will improve the soil, attract pollinators, and it needs no care at all, once it is established.

The aroma of lilacs is intoxicating, and fleeting.

Lilacs may only bloom for a couple of weeks, usually near the end of May, but they are worth the wait. These cousins to olive trees and privet shrubs add beauty in a landscape, and the heady blooms are bound to attract pollinators.

Growing lilacs in containers

To successfully grow lilacs in containers, you will need to select a dwarf variety and a large container. Lilacs prefer having room to spread their roots, so the container needs to be at least 12 inches deep and 24 inches wide. Be sure to use potting soil with a neutral pH. Lilacs dislike both alkaline and acidic soil. Water thoroughly at planting time and keep the soil evenly moist (not soggy) until the roots have taken hold. After that, water any time the top inch of soil dries out, and not before. Containerized lilacs need at least 6 hours of full sun every day to bloom properly. Many homes do not have that much direct sunlight, so you may need to supplement with grow lights. Stabilize temperatures and reduce moisture loss adding a thin layer of mulch, such as attractive redwood chips, around your potted lilac, just be sure to leave a little space between the mulch and shrub stems.

Caring for lilacs

Lilac flowers bloom on old wood, so pruning should be kept to a minimum. Pruning should be limited to removing dead, diseased, rubbing branches, suckers, and spent flowers. Since flowers are produced on older wood, do not put off deadheading your lilacs. If you wait until the end of the season, the wood that grows in will be too young to produce flowers the next season. If your lilac becomes unruly, cut all canes back to eye level and remove one-third of the oldest canes at ground level. The next year, cut half of the remaining old wood down to the ground. In year three, cut the remaining old wood. Or, you can cut the whole thing back to a height of 6 to 8 inches. This more drastic method creates the best blooms, in the long run, but it will take your lilac a few years to get back to full size.

Each spring, top dress the soil around lilacs with aged compost. Then, cover that top dressing with mulch. This will add nutrients and protect the microorganisms that help your lilacs get to those nutrients. Commercial fertilizer is not recommended for lilacs planted in the ground. Excessive nutrients causes plants to produce more leaves, and no flowers.

Lilac pests and diseases

I have found Fuller rose beetles to cause the most damage to my lilacs. Scalloped leaves are a sure sign of this pest. Lilacs are also susceptible to powdery mildew, phytophthora, and pseudomonas. Slugs and snails are said to cause some damage, but I have not had that experience.

Propagating lilac

If you already have a lilac, you can take root, shoot, and sucker cuttings to propagate new plants. Dig up some roots, or suckers with roots attached, and place them in a bucket with some water until you are ready to plant. You can also use 8 to 12 inches new growth twigs. Simply strip away most of the lower leaves and place them in rich potting soil and keep them moist (above and below ground) until roots start to grow. Since woody stems can be difficult to start rooting, many people apply rooting powder to the lower portion of the stem. Since rooting powders are synthetic plant hormones, I don’t use them.

While lilacs are not edible, I can practically taste their sweet fragrance. Also, the pollinators who are drawn to lilac blossoms often stick around to pollinate other plants in your garden.

Italian pear scale may sound like a lovely antique find at your local flea market, but this pest can reduce tree vigor and fruit size..

While it is easy to figure, from the name, that this pest attacks pear trees, it can also be found on walnut, prune, and apple trees.

Italian pear scale description

Italian pear scale (Epidaspis leperii) females are purple, pink, or reddish. Like other scale insects, they spend most of their life hidden under a tiny, gray, circular cover, with an off center peak. This cover is only 1.5 mm in diameter. For us Americans, that works out to only 1/16 of an inch! To make finding them even more difficult, they may be hidden under moss or lichen. Male flying scales are too small to see.

​Damage caused by Italian pear scale

This insidious pest does not attack fruit or nuts. Instead, in the relative safety of their dome-like home, they feed directly on the wood of the tree. Large infestations can lead to cracks in the bark, which allows other pathogens to enter. The strain on the tree also reduces growth and production, resulting in smaller sized fruit or nuts.

Controlling Italian pear scale

After leaf drop, monitor trees for scale infestation. You may need to scrape off moss or lichen to see these tiny pests. These scale insects seem to prefer scaffold limbs (the larger, horizontal branches). Heavy infestations can be treated with Bordeaux mixture.

Citrus thrips description
​
First, citrus thrips are very difficult to see. They generally hide underneath leaves and leap away, flying to another hiding place when they feel threatened. Since their wings are really not designed for actual flight, thrips use a method called “clap and fling” to become airborne. Basically, a thrips claps its wings together, above its back, and then flings them apart, over and over. This creates enough lift to get somewhere else, but that’s about it. If you actually get ahold of one, you will see that they have 2 pairs of very skinny, fringed wings and a narrow, cigar-shaped body. Newly emerged adults are pale yellowish-green, while adults are black with red markings.

​Citrus thrips life cycle

Citrus thrips go through an incomplete metamorphosis called hemimetabolism. This means they have three distinct life stages: egg, nymph, and adult. Thrips are able to reproduce sexually, asexually, or bisexually. Dozens of eggs are inserted into leaf tissue. When they hatch, generally around March, the oval-shaped, clear yellow larvae start feeding on new growth, called “flush.” This causes distorted leaves and buds. Once the larvae have eaten their fill, they enter a resting pupal stage before becoming adults. With California’s mild climate, there can be as many as 8 generations of citrus thrips each year. That’s a lot of thrips!

Blackleg of cabbages

All plants in the cabbage family, except horseradish, are susceptible to blackleg. This disease used to wreak havoc across the country. Once scientists determined that fungal spores (Leptosphaeria maculans) were the cause, seed growers started treating cruciferous seeds with hot water. This treatment reduces the chances of disease but does not eliminate it.

Since cabbages don’t have any legs, you may wonder how this name came about. The word blackleg refers to the dark lesions visible on stems at the soil level. Each part of the infected plant has its own set of symptoms:

• Seedlings - pale gray lesions cover and kill young seedlings.
• Stems - long, brown, sunken lesions with purple or pinkish margins
• Roots - dark cankers form on root crops, slowly destroying all root systems
• Leaves - tan, circular leaf spots turn ashy as the tissue dies; chlorosis
• Heads - heads may look healthy at harvest, but tissue turns black in storage

Infected stems are prone to snap. If you cut into the vein of an infected plant, you can see the blackened xylem - just be sure to disinfect your tools afterward!

The fungal spores of blackleg often find their way into your garden on seeds. Once they arrive, they hitchhike on tools, splashing water, wind, or infected plant material that has been cold composted. These fungi can also gain entry into otherwise healthy plants through cabbage maggots, cutworms, cabbageworm, and other pest-feeding holes. It only takes a few fungi, with the right amount of warmth and moisture, to create an epidemic in a seed bed, garden row, or agricultural field.

Stratification is a process that fools seeds into thinking they have experienced winter, spring, or both, to help them break dormancy.

Traditionally, stratification referred to the practice of layering seeds with a moist growing medium, such as vermiculite, peat, perlite, sawdust, composted bark, or potting soil. As seeds germinated, they would be removed to a more permanent growing space. There are three types of stratification: warm, cool, and variable.

Learn from your plants
​
Many plants have evolved to use cold temperatures as a period of rest and warmth as a trigger to gear up for germination in spring. We still don’t completely understand the magic that happens within a seed. [Part of me hopes we never do!] Simple starches, sugars, and genetic information are somehow transformed into a living, breathing, growing organism. It’s really amazing when you think about it. We can look to those natural processes to get more out of our gardens. There’s no sense bucking millions of years of evolution. Even better, we can put all that evolution to work for us. Keep in mind, however, that some seeds need the extra time for the embryo to fully develop. Pushing them to do too much too soon only weakens them.

Benefits of stratification

​By artificially stratifying seeds, you can decide when they will germinate. This can help you control when a crop might reach harvestable size. It can also help avoid predictable pest or disease infestations. It can also be sued to extend your growing seasons. Since seed dormancy can be quite variable, with some seeds taking over a year or two to germinate, stratification can be used to provide a more favorable environment for new seedlings.

Preparing seeds for stratification

Start with firm, certified disease-free seeds. These seeds will need a little moisture for their period of hibernation, but too much moisture sets the stage for decay. Seeds destined to be stratified need to be soaked for 24 hours. Then shake off excess water and place them in a plastic container with three or four times the seed volume of some type of growing medium. Some people use folded paper towels, which you can certainly use. Professional growers prefer sphagnum moss or vermiculite. Whichever you prefer, add water to the plastic bag and allow the medium some time to absorb all that moisture. Vermiculite absorbs water quickly, while moss may take 8 to 10 hours. Next, squeeze the bag to get rid of most of that water, the same way you would squeeze out a sponge. Gently shake the seed-medium mixture, to distribute the seeds and to incorporate air, before placing the bag in the appropriate temperature-controlled environment.

Be sure to write the seed name and the date stratification was begun on the bag. The next day, pour or squeeze out any excess water. Then, let nature take its course. Periodically check your seeds for signs of rot, desiccation, or germination. Rot should be completely wiped off and the seed allowed to dry out before continuing stratification. Otherwise, the seed can be planted after all signs of decay have been removed. Dried out seeds need more water and closer monitoring. Germinating seeds need, you guessed it - planting!

Cold stratification

Most perennial woody shrubs and trees require cold stratification to germinate. Lettuce, milkweed, delphinium, and violets can also benefit from this process. Cold stratification mimics the conditions of a cold (31 to 41°F), wet winter and is generally used on seeds that naturally ripen in late fall or early winter. Your refrigerator provides the perfect place to cold stratify crops intended for spring planting. You can leave moistened seeds in the refrigerator for 1 to 4 months to get the desired effect. Just make sure they are not sitting in water, or they will rot. Also, do not plant cold stratified seeds in autumn. The double whammy of cold will be more than most seeds can handle.

Warm stratification

Warm stratification is used on seeds from trees and shrubs that naturally ripen in early fall. This is the majority of plants grown in gardens and landscapes. Warm stratification mimics the conditions of spring with warmth (68-86°F) and moisture. The moisture softens the seed hull, entering the seed and providing the water needed by the embryo to complete its development. Moistened seeds can be placed in a plastic container on top of the refrigerator for 60 days, or until 20% germination is seen. When warm stratifying seeds, you will need to keep a look out for mold, which will need to be wiped off regularly. Some growers apply fungicides to seeds being stratified. I do not.

Variable stratification
​
In some cases, seeds need a combination of warm and cold stratification to stimulate germination. Starting with warm stratification, moistened seeds are given 60 days to soften the seed hull before being placed in a cold environment.

To determine whether or not stratification is needed by your seeds, find out how it grows in nature.

Blister beetle lifecycle

​As far as insects go, blister beetles have a pretty interesting life. Female start the cycle by depositing fertilized eggs in low spots in the soil. The eggs hatch into larvae (called triungulin) , who hunt for underground cricket and grasshopper, and bee eggs. As they feed, they go through three growth stages before turning into sedentary pseudo pupae. This is their overwintering stage. As temperatures rise in spring, the pseudo pupae enter a true pupal stage before reaching adulthood. Adults feed on flowers and vegetable plants and breed throughout summer, depositing eggs in the soil, and the cycle continues.

Harlequin bugs are black and red stinkbugs that feed on members of the cabbage family.

Harlequin bug description

The telltale shield-shaped back of the stinkbug family (Pentatomidae) make it easy to identify this garden pest. Also known as calico bugs, harlequin cabbage bugs, and fire bugs, harlequin bugs (Murgantia histrionica) are shiny black with yellow, orange, and red markings. They are often confused with Bagrada bugs, but harlequin bugs are significantly larger, and they lack the white markings of Bagrada bugs. Adults can reach 3/8 of an inch in length. If you allow yourself to get past the bit about how these are pests, they really are strikingly beautiful. That being said I still feed them to my chickens whenever I see them.

Like us, plants are subject to many bacterial diseases.

Bacteria are found everywhere on earth. Some bacteria live on the edges of volcanoes, and others thrive in jet fuel. (How’s that for resilience?) Luckily for us (and our plants), most bacteria are beneficial. Even as you read, millions of bacteria live on and in you, helping you to be healthier.

Plants have beneficial bacteria, too. Legumes, for example, have a relationship with Rhizome bacterium that helps them convert atmospheric nitrogen  into a form they use for food. Bacteria can also disfigure, dwarf, and even destroy many of your plants. 

Most plant diseases are bacterial, viral, or fungal infections. Fungi are responsible for 85% of all plant diseases. That said, approximately 100 species of bacteria can cause trouble for plant growers.

What are bacteria?

Bacteria are tiny one-celled beings without a clearly defined nucleus that can reproduce rapidly by simple cell division. They come in several shapes. They can be rods, spirals, spheres, or filamentous (“whiptails”).

The first bacterial plant disease ever identified was fireblight (Erwinia amylovora). This discovery occurred around 1877, just after anthrax, the first bacteria identified. Since then, we have learned more about how these one-celled creatures help and harm our food crops and ornamental plants. But, to cause harm, they must first gain entry.

How bacteria enter plants

Unlike viruses, which inject genetic material to reprogram cells to make more viruses, nearly all bacteria grow in the spaces between plant cells, working to destroy the cell wall and consuming its contents. [One species, Agrobacterium, comes close to crossing the line between viruses and bacteria by genetically modifying their hosts to cause cancer-like growths called crown galls.]

Most bacterial diseases are transmitted by sap-sucking insects. Aphids, leafhoppers, nematodes, and psyllids are the most common disease vectors. Once these pests are infected, they carry disease to every plant they visit. As they feed, bacteria invade the plant tissue. 

Bacteria can also enter plants through natural openings, such as stomas and injuries caused by limbs rubbing together, thorns, or wind damage. Onion maggots, cabbage maggots, caterpillars, crickets, slugs, and other pest-feeding damage can also open the way for bacteria. Other physiological conditions that provide entry for bacteria include citrus fruit split, mummies, and your very own pruning shears!

How smart can one cell be?

One bacteria (Pseudomonas syringae pv. tomato), responsible for bacterial speck, causes massive annual losses. Researchers at Virginia Tech discovered that this pathogen has figured out how to drop the bits of its genetic information used by tomatoes to recognize it as a threat!

How bacteria damage plants

Once inside, most bacteria grow between plant cells, in the apoplast, or within a plant’s vascular system. As vascular bacteria reproduce, they clog the xylem, phloem, or both, depending on the specific pathogen. Clogging the xylem blocks water rising from the ground while interfering with the phloem blocks access to sugars produced by photosynthesis, starving the plant.

Bacterial families

During medieval times, people believed bathing removed a protective coating that saved us from the Evil Spirits that caused death and disease. [Thank goodness those days are over!] In the same way, scientific research is changing the way we look at many bacteria. At this point, the most destructive plant bacteria fall into one of these families:

• Agrobacterium--crown gall in peach and nectarine, walnut, flowers, and many perennial, woody plants
• Clavibacter—bacterial canker of tomato
• Erwinia--fireblight in apple and pear
• Pectobacterium—bacterial soft rot in potato, onion, garlic, and many other crops
• Pseudomonas—bacterial blast, blight,, and canker in tomatoes, stone fruits, and many other tree crops
• Xanthomonas--black rot of crucifers and other crops

You will often see these words included in the names of the diseases they cause. Two other unique bacterial families are fastidious vascular bacteria and phytoplasmas.

Fastidious vascular bacteria

Until 1967, diseases caused by fastidious vascular bacteria were considered viral. Pierce’s disease, which attacks grapes, and almond leaf scorch are two diseases that fall into that category.

Phytoplasmas

This group of bacteria causes plants to produce more axillary buds, creating a bushier appearance and weakening the plant. Commercial greenhouses use phytoplasmas to generate plants with lush, thick growth. These bacteria also cause vivipary in strawberries. The same group of bacteria, carried by leafhoppers, cause corn stunt, cherry X-disease, and aster yellows in lettuce, celery, and other plants.

Symptoms of bacterial infection

Bacterial infections can be difficult to see at first. Water-soaked lesions or bacterial ooze are often the first signs. Other symptoms include leaf and blossom spots with yellow halos, cankers, galls, soft rots, the classic shepherd’s crook stem ends of fireblight, and wilting. Symptoms vary depending on the type of bacteria involved. 

Since bacteria are alive, they are constantly evolving to get the better of their hosts, pushing plants to develop better defenses, which motivates the bacteria to get better at what they do, and so on.

Conditions that promote bacterial disease

Most bacterial diseases occur in spring because temperatures are rising, insects are active, there is enough moisture, and new, vulnerable buds and leaves are emerging. Most bacterial diseases prefer temperatures between 55°F and 85°F, with a high relative humidity.

Preventing and controlling bacterial disease

Bacterial diseases are difficult to control once they occur. Your garden plants will be far better off if you can prevent these diseases in the first place. The following good cultural practices can make a big difference in the number of diseases infecting your plants:

• Use certified pest- and disease-free seeds and seedlings.
• Quarantine and harden off new plants.
• Plant resistant varieties.
• Plant at appropriate times. 
• Use recommended plant densities.
• Monitor plants regularly for signs of infection.
• Provide adequate airflow through proper pruning.
• Irrigate plants properly, allowing the soil to dry out between waterings.
• Employ crop rotation to reduce overwintering.
• Remove weeds.
• Avoid working crops when they are wet.
• Isolate and destroy infected plants.
• Clean and disinfect tools regularly.
• Apply least-damaging treatments, such as fixed copper or Bordeaux mixture, only when necessary.

Of bees, disease, and marigolds

Many garden resources point to honey bees and marigolds as protection from bacterial disease. There is even some measure of truth to these claims. Initial research published in the Journal of Food Engineering suggests that the pollen bees carry with them may have antibacterial properties. Other research from the University of Florida shows that bees are the primary vectors of fireblight and southern bacterial wilt. As they move from flower to flower, they carry disease-causing bacteria. 

Marigolds provide some protection against nematodes. Research conducted at the University of Florida found that planting a cover crop of marigolds (Tagetes patula or T. erecta) can reduce nematode populations. Before you start, however, you must identify the specific nematodes in your soil to select the correct marigold variety to get the desired results. It makes a difference.

If you suspect bacterial disease in your garden, take a closer look and monitor things regularly. You can often break the disease triangle once you know what is growing on and in your plants.