White rust? Rust isn’t white. Rust is orange!

The rust on an old car is orange. Fungal rust spores that grow on the underside of rose leaves are bright orange.

But white rust isn’t orange or fungal.

White rust, white blister rust, or blister rust, is a disease that attacks plants in the cabbage family, causing white blisters, deformed growth, and leaf loss. Wet leaves and cool temperatures set the stage for white rust to strike broccoli, cauliflower, collards, radish, and turnips. Arugula and rapini are especially susceptible to white rust.

White rust pathogen

Scientists thought white rust (Albugo candida) was a fungal disease until molecular research discovered that it is an infection by tiny algae-like microbes called oomycetes that parasitize vascular plants. Downy mildews are also caused by oomycetes. The reproductive spores created by white rust can lay dormant in the soil during the dry season, waiting for the rainy season.

White rust symptoms

As flowers and leaves become infected with white rust oomycetes, white blisters (pustules) form under the plant’s skin on the underside of leaves. The blisters appear waxy and may be pinkish at first. Upper leaf surfaces exhibit pale green or yellowish spots that can reach 1 inch in diameter.

These blisters contain baby oomycetes. When the blisters pop, oomycete spores take to the wind, infecting nearby plants. Spores can also move to other plants by splashing water from irrigation or rain. 

[White rust should not be confused with Chrysanthemum white rust (Puccinia spp.), a fungal disease with masses of blisters that may be black, brown, purple, orange, or yellow.]

White rust controls

There are currently no resistant plant varieties available. Commercial growers rely on fungicides to control this disease. You can reduce the likelihood of infection simply by decreasing how much time leaves stay wet. Rather than overhead watering, use drip irrigation or soaker hoses. These methods save water, too. In severe cases, an area may need to be left fallow, or you can use crop rotation..

​Annual sowthistle (Sonchus oleraceus) is also known as milk thistle, hare’s thistle, soft thistle, and hare’s colewort. As a member of the sunflower family, sowthistles have a taproot and they produce a milky white sap (latex).

​Annual sowthistle description

If you live in California, you’ve probably seen millions of these. Sowthistles can grow in only 1/2 an inch of soil, and they grow quickly. The cotyledons (seed leaves) are slightly football-shaped and less than 1/3 of an inch long. Early leaves are alternate, somewhat hairy, and feature margins (leaf edges) with backward facing teeth. Like dandelions, the stem is a smooth hollow tube. Mature leaves are a grayish blue-green. Upper leaves are smaller than lower leaves and there is no petiole (leaf stem). In many cases, the stem looks as though it is poking through the middle of the leaf, making them perfoliate. Lower leaves are deeply lobed and tapered. The flowers are yellow clusters that close at night (nyctinasty). These flowers matures into fluffy seed heads that blow in the wind, just like dandelions, but the seed heads are generally not a complete sphere.

No Southern supper would feel right without an occasional serving of collard greens. And no New Years Day celebration would be complete at my house without a big pot of Hoppin’ John, which combines rice, blackeyed peas, and collard, mustard, or turnip greens. Traditional folklore claims a bowl of Hoppin’ John on January 1st ensures prosperity in the coming year. It is certainly packed with protein, fiber, vitamins and minerals. Personally, I just love how it tastes! What many people don’t realize is just how healthy collards are for you, or how easy they are to grow at home.

How to grow collards

Collards can tolerate temperatures as low as 5°F, but they will bolt in our California summer heat. Bolting does not affect leaf flavor (and it can give you seeds for your next collard crop), but collards are generally a cool season crop. A light touch of frost actually sweetens the flavor of collard greens. Here in the Bay Area, collards can be planted February through April, and again in September and October. These plants can get relatively large, with broad, waxy, dark green leaves. They prefer lots of sunlight and need plenty of organic matter in the soil. You may need to acidify the growing area, as collards perform best in soil with a pH of 6 to 6.5.

Plant collard seeds 1/4 to 1/2 inch deep. You can start seeds in cell flats and then transplant into your garden or foodscape. [Since seed packets nearly always contain far more seeds than you will ever need or use, hold a seed swap with friends and neighbors!]  If you direct sow, plants should be thinned to 18 to 36 inches apart, depending on the variety. Side dress plants with aged compost or manure every 4 to 6 weeks, and mulch around plants to reduce competition from weeds and to maintain moisture levels and temperatures. Collards have a shallow root system and water-stressed collards taste far more bitter than properly irrigated plants.

Collard pests and diseases
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As with other members of the cabbage family, collards are frequently fed on by aphids. You can blast these pests off of plants with a powerful stream of water from the garden hose, or you can apply insecticidal soap. Cabbageworms, slugs, and cabbage loopers can be handpicked. [I feed them to my chickens.] Flea beetles, bagrada bugs, whiteflies, and cabbage root maggots can also be a problem. Research conducted at UC Davis found that flea beetle and aphid populations can be reduced when collards are interplanted with beans. They found that the same was true for weeds, but I’d rather have beans than weeds! Apparently, the mixed plantings work better at attracting parasitic wasps, making crops harder to find, and by providing other food sources for the pests.

Diseases that affect collards include white rust, blackleg, cabbage yellows, and clubroot. You can reduce the likelihood of these diseases occurring by rotating crops in the cabbage family into a different growing space each year.

Harvesting collards

Most collard varieties are ready to harvest in 55 to 75 days. Collards are one of those cut-as-you-go crops. Just keep picking outer leaves, as you want them, and the paints will continue producing more for several months. It is a good idea to allow plants to reach a height of at least 10 inches before harvesting leaves. If you find that you have more collard greens than you can eat, you can always cook them and then freeze them, for longer storage. Your friends and neighbors may appreciate some, as well!


Collards are large, attractive plants. They do not need to be sequestered into traditional garden rows. Find a nice, sunny spot in your landscape and make it home to your very own collard plant!

Why do people paint their trees white?

Is it a rural fable? A picket fence prank? Or, is there real science behind the idea of painting tree trunks white?

It ends up, there are very good reasons for painting both the trunk and the upper sides of exposed branches with a certain type of white paint to protect against sunburn, pests, and disease.

Benefits of whitewashing

An annual application of whitewash reduces sunburn damage by reflecting sunlight away from the tree. Sunburned bark frequently splits and curls, providing easy access for numerous pests and diseases. This is especially true for borers, such as shot hole borers and flathead borers, as well as moth larvae, beetles, and horntails. Whitewashing has also been found to discourage rodents, such as voles, mice, and rabbits, from gnawing on the trunk. The paint also helps protect against frost damage.

​What type of paint should be used?

Whitewashing is one of those ‘too much of a good thing is a bad thing’ situations. Using enamel (the wrong paint) can kill young trees. So can using latex (the right paint) if it is undiluted. Traditionally, whitewash was made from slaked lime and chalk. It was a poor man’s paint that tended to rub off onto your clothing if you brushed against it. While this material has mild antibacterial properties, mixing it can be messy.

When you head to the paint store, or go digging around in your garage, make sure that you only use interior latex, and not enamel or exterior latex. Exterior paint may contain harmful additives. The important thing to look for is the "VOC" - these letters stand for "volatile organic compounds". These compounds can be dangerous to trees and humans. Paints listed as being VOC-free or being low in VOCs are better choices, health-wise.

Whitewashing should only be done with interior latex paint that has been diluted with water. Use a mixture of half water and half interior latex paint.

The paint and the sticky barrier will need to be reapplied each year, to maintain their usefulness.

Currants are a refreshing berry used to make jams, jellies, pies, and wine, but currant borers can really put a dent in your crop.

In California, the invasive currant clearwing moth (Synanthedon tipuliformis) makes its appearance each April, laying eggs in bark crevices, at old pruning cuts, and in narrow branch crotches. While individual moths only live one week, overlapping generations can extend egg-laying through August. These pests bore into the canes of currants, and sometimes blackberries.

Currant borer damage

When the eggs hatch, larva chew entry holes in canes, burrowing into the cambial tissue and sapwood. Here, they will feed on sap and vascular tissue for the rest of the summer, and then overwinter within the canes. In March, they will resume feeding, going through several instars, before entering a pupal stage. All this boring and feeding can girdle branches, causing twig and branch dieback. It also restricts the growth of infested plants, resulting in fewer blooms (ergo, less fruit). You may be able to see sawdust-like frass mixed with sap oozing out of entry holes, and longitudinal scars on infested twigs and branches.

Currant borer controls

Once a branch is infested, it should be removed and destroyed, or thrown in the trash. Severely infested plants should be removed completely. Once borers are inside a plant, there isn’t much you can do. Some people try shoving wires into entry holes, trying to stab the larva, but this is only marginally effective. Woodpeckers enjoy catching adult moths on the wing and braconid wasps parasitize these pests. There are also some beneficial nematodes that are available commercially. I’m not sure which species of nematode will work against currant borers, but you basically inject the live nematodes into the borers’ holes and spray the branches with nematodes in solution. Nematodes are fiddly and I have not had good luck with them, but they may work for you. Rather than losing valuable plants, it is far easier to prevent borer infestations int the first place.

Healthy plants are better able to protect themselves against infestation, and rapid growth tends to make stems susceptible. Caring for your currant plants in a way that keeps them healthy and growing at a steady pace, rather than overloading them with fertilizer for faster growth, is the best way to prevent infestations. Also, avoid water stress with regular irrigation, especially during the peak of summer. Whitewashing the trunks of mature tree-trained currants with a 50:50 mix of water and latex interior paint can help reduce sunburn damage, which is more susceptible to infestation.

Pheromone traps can be used to monitor for this pest. Just remember that the down-side of using pheromone traps is that they end up attracting pests from a greater distance. According to the U.S. Dept. of Agriculture, insecticides should be applied 7 to 10 days after the first male moth is captured in a pheromone trap. If you decide to use an insecticide, please, Please, PLEASE, follow the directions on the label exactly. Insecticides are poisons.

Finally, regularly inspecting your currants and blackberries for signs of infestation can give you a unique opportunity at borer control. Just before clearwing borers emerge, they have a habit of pushing themselves halfway out of their tunnel and just sitting that way for a bit - catching their breath, I assume. So, look for areas of damaged bark and frass. If you see a borer half-way out of a twig, cane, or branch, help it out the rest of the way and then feed it to your chickens or stomp on it.

Step 1: What are you already growing?

Before you add something new, it helps to identify what you already have. Established perennials, sun exposure, and soil health will often dictate the conditions available for new plants. Trees and shrubs that are already in place need to be taken into account. They may provide the perfect protection for a collection of shade-loving plants, while sun-loving varieties would wither in theat shade. Speaking of shade, just how much sun does each area of your garden get each day? It changes with the seasons. Knowing just how much sun each area gets can help you select plants more likely to thrive. Most garden plants need 6 to 8 hours of full sunlight each day to be healthy. Also, keep in mind that some plants use a form of chemical warfare, called allelopathy, to reduce competition from neighboring plants. Learning a little about allelopathy can increase the likelihood that your plants will thrive.

I’ve said it before and I’ll say it again: Take a soil sample and send it to a local, reputable lab. [Over-the-counter soil tests, with those little plastic tubes, are not accurate enough to be useful.] The results of your soil test will help you prepare better for those new arrivals, as well as help your established plants. Wood chips, mulch, or a ground cover may be just what is needed. Here, in San Jose, California,, acidification is often recommended for many popular plants.

Step 2: What do you want from your garden or landscape?

For me, the answer to that question is simple - I want edible plants that my family will enjoy eating. Your reason for gardening may be something entirely different. Do you want an herb garden? A flower garden? Do you want maintenance-free plants that will look good year round? Taking the time to decide what you want from your landscape or garden design through each season will help you select the best plants. I use my shopping list. If I write a fruit or vegetable on my shopping list with any frequency, I ask myself if it is something I can grow at home. Nearly always, it is, so I do! [If you are at a loss on this one, take a look at the list of garden design prompts, below.]

Step 3: Zones, pathogens, and cultivars

Before shopping for plants, you should also consider your region. If you live in the United States, you can use the U.S. Hardiness Zone map. This tells you which growing zone you are in. Growing zones are based on average annual winter temperatures and they help you select which plants will thrive in your location. You should also check out resources from your local County Extension Office. They can often provide you with information about common pests and diseases, specific to your area. You can use this information to select cultivars that are resistant to the pathogens common to your area. Also, avoid installing non-native invasive plants. While reputable plant sellers are taking these plants off their shelves, not all sellers care.

Step 4: Start shopping and planting!

Finally! Now that you know what you are working with, what you want, and what will grow well in your area, you can finally start shopping for or collecting your new plants! Remember, catalogs and garden centers are not your only source for plants:

• Check out your local Master Gardener plant sales.
• Get seeds, seedlings, and cuttings from fellow gardeners.
• Shop your local farmers’ market.

When shopping for new plants, watch for signs of pests or disease. You don’t want to introduce a new problem along with the plant. Many plant pests and diseases are brought in on contaminated soil and plants, which is why a quarantine period is such a good idea. It allows you to break the disease triangle before it affects the rest of your garden.

Garden design prompts

Sometimes, we just don’t know where to begin. I think this is especially true when we have an overwhelming number of options. If you have absolutely no idea what you want to do with your landscape or garden design, see if any of these themes spark inspiration:

• children’s garden (sunflower forts; fairy gardens)
• color palette garden (all shades of your favorite color)
• storybook garden (Beatrix Potter, Mother Goose, Edgar Allen Poe)
• tea garden (peppermint, chamomile…)
• pizza garden (tomatoes, oregano, thyme, sweet peppers, olives)
• salad garden (lettuces, spinach, chard, carrots, celery)
• stir fry garden (peppers, celery, onion, carrots)
• gift garden (plants to give to family and friends)
• low-maintenance, drought-tolerant garden (succulents and native plants)

Rather than grabbing the first plant that catches your eye, taking the time to learn about what your microclimate has to offer and deciding what you want from your landscape or garden design can help ensure that the plants you actively choose to add will be appropriate, rewarding, and healthy.

Native plants have evolved, over thousands of years, to live in relative balance with local soil, climate, plants, animals, and insects.

These are not plants from other regions or other continents. They are often not even plants native to nearby towns or counties. These are not plants that were developed in a laboratory.

Going native

Going native doesn’t mean you have to stop growing your grandmother’s heirloom tomatoes or patches of delicious basil. It simply means using native plants as your first choice. Hardcore enthusiasts insist on growing nothing but natives. Personally, I find that level of commitment too limiting. Instead, I look for a workable balance. You can find information about native plants from your County Extension Office and local native plant societies. Here are some tips for gardeners looking to add native plants:

• Use native plants that are as local as possible.
• Pair native plants that grow together naturally, using similar soil, sun, and water resources.
• Avoid installing invasive plants.
• Minimize pruning to avoid interfering with wildlife.
• Allow leaf litter to remain where it falls, where it will feed the soil and improve soil structure.
• Avoid using chemical pesticides, fungicides, and insecticides.
• Install native plants that will attract native pollinators.
• Make your landscape fire safe.

Many times, native plants are free for the taking, if done responsibly.

Each kernel of corn is a specialized type of fruit, called a caryopsis. So are rice, oats, barley, and wheat.

Unfamiliar fruits
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Fruits are the seed-bearing structure of angiosperms (flowering plants), made from the ovary (pericarp) of a fertilized gamete. Fruits taste good because that makes them more likely to be eaten, spreading seeds far and wide. We are all familiar with fruits. Apples, peaches, olives, and avocados are all fruits, but so are cereal grains.

Cereal fruits

Unlike apricots and nectarines, which have thick, juicy fruit walls, cereal grains have a very thin, dry fruit wall, or husk. A caryopsis is a simple fruit. This means they develop from a single pistil. Because there is no seam to split open and release the seed within, it is called indehiscent. Botanically, the outer skin of corn kernels and grain seeds is the pericarp, or husk. The husk is firmly attached to the seed coat. That is why special milling processes must be used to get at those edible seeds.

While blossoms and blooms and weeds and new seedlings have been telling us for days or even weeks, it is finally official. Spring has arrived! [Or, autumn, if you live in the southern hemisphere.]

Spring equinox is the moment when the Sun passes the Earth’s equator, moving from south to north, with no apparent tilt to the Earth axis.

Planetary tilt
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Normally, we feel the Earth’s tilt as different seasons. Half of our trip around the sun is spent tilted slightly away from the sun (colder weather) and the other half is spent with a similar tilt toward the sun (warmer weather). Today, because we see the sun passing our equator, day and night are the same length. Sort of. That is why it is also called the spring equinox. I say ‘sort of’ because the day will actually be longer than the night. This is because of the sun’s light being refracted through the atmosphere before and after it has risen and set. If you want to know more about the Earth’s tilt and seasons, check out my post on winter solstice.

Spring fever

So, you’ve been waiting for months, browsing seed catalogs and dreaming of all the plants you want to try this year, along with some old favorites. Spring is a busy time in the garden, to be sure, but don’t be hasty. Don’t let all those visions of a summer harvest cloud your view. While the Bay Area’s last frost date was nearly a week ago, I woke to see frost all over my garden only yesterday morning. Nature does not obey our rules. We must keep our eyes and ears open and be aware of what is happening in our microclimate. That being said, it is now time to start planting! Or, is it?

Before you start planting….

Speaking of frost, what about those plants that were damaged by frost over the winter? All that damaged plant tissue should be removed now to reduce rot in the garden. It makes things look nicer, too. But are your tools sharp enough for the job? A quick fix with a file or sharpening tool makes the job so much easier, and a little 3-in-1 oil will protect those tools from moisture damage. And are your planting beds and containers actually ready for plants? Adding some aged compost before you start planting will do your plants and your soil a world of good for the upcoming growing season. While you’re outside, take a look at your citrus trees. Do they need pruning? Now is the time to do it. And, while you’re at it, keep a look out for mummies. These fungal factories can contain millions of spores. This is also the time to watch for things like mummy berry and black spot. Recent rains make this a time of fungal growth. Slugs and snails like it, too, so be prepared!

Clover description

Clovers are also called trefoils because they nearly always have leaves in groups of three. [A four-leafed clover is said to be quatrefoiled.] Clovers are legumes, along with peas, beans, and alfalfa. This means they have a symbiotic relationship with certain Rhizobium bacteria that allows them to fix atmospheric nitrogen and use it to grow. For the most part, clover seeds start to germinate in the fall, and continue until temperatures rise above 60°F. Clovers are classified as annual, sweet, or perennial.

Beneficial clover
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Adding clover as a ground cover or a green manure can mean future plantings will thrive or, as the saying goes, “They will be as happy as a pig in clover.” Of course, bees love clover flowers, so be sure to plant your clover where you are less likely to step on a bee.

Clover controls

If clover is causing problems in your garden or landscape, the best control methods are hand-pulling, hoeing, and mulch. The mulch needs to be 4 to 6 inches deep to block clover. Clover seeds are very rugged, so composting and solarization are generally not effective controls.
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If you have bright green clover popping up in a yellow lawn, your soil is probably low on nitrogen.

Did you know that a group of clovers is called a cluff? I didn’t either.

Bermuda buttercup is a sunny yellow flower that appears in many warm regions, each winter and spring.

Originally planted as an ornamental (oops), we now know that this South African invasive weed has the potential to make life quite difficult for our native species.​

Also known as sourgrass, Buttercup oxalis, Oxalis cernua, or simply oxalis, this low growing perennial is difficult to control. [The oxalis family is actually quite large and we will discuss that another day.] Close cousin to creeping woodsorrel, oxalis contains relatively high levels of oxalic acid, which is what gives it its sour taste. That is also why they should not be consumed in large quantities by livestock or your backyard chickens.

​Bermuda buttercup description

Three heart-shaped leaves that resemble clover make Bermuda buttercup (Oxalis pes-caprea) easy to identify. Most Bermuda buttercup plants have a loose rosette of basal leaves and tall stems, usually a foot tall, that feature bright yellow, 5-petalled flowers. You may see brown or purple spots on the leaves. Tiny bulblets form around the stem and more bulbs develop underground. Bermuda buttercup plants produce an average of 10 to 20 bulbs each year. Bermuda buttercup also spreads using runners and through contaminated soil.

Controlling Bermuda buttercup

This weed is very difficult to control, once it takes hold. Pulling the weeds does little to eliminate them, since the bulbs left behind are perfectly capable of starting the whole process over again. While Bermuda buttercup is rarely a problem in lawns, in can quickly become a serious problem in landscapes and home gardens. In the past 10 years, this invasive weed has choked out many native plants.

Homeowners are urged to eradicate this weed, to help prevent its spread into wildlands, where permanent damage may occur. Use the methods below to control Bermuda buttercup on your property, and please educate your neighbors, before it is too late.

• dig up plants as they are seen, taking care to remove all visible bulbs [repeat as needed]
• do not use contaminated soil elsewhere in the garden, without sifting it clean
• remove flower buds as soon as they are seen, to reduce bulb development
• soil solarization is the only effective removal method.

You will rarely hear me suggest herbicides, but this is one case where their proper use may be warranted. Always read the label and follow directions exactly. Seriously.

If you really must have pretty yellow flowers in your garden or landscape, please don't let it be Buttercup oxalis.

Conifer species

While some plant families include thousands of species, the conifers boast only 7 or 8 subfamilies (depending on which botanist you ask) and most of us recognize even fewer. There are less than 630 living species of conifer worldwide. These include pine, cedar, redwood, larch, cypress, fir, Douglas-fir, kauri, juniper, hemlock, yew, and spruce. All conifers are in the Pinales order and the Pinaceae family. Botanists break down the subfamilies in this way:

• Abietoideae - fir
• Cedrus - cedars
• Cupressaceae - cypress
• Laricoideae: 
  
  • Larix - larch
    
  • Pseudotsuga - Douglas-fir
    
  • suga - hemlock [Not to be confused with poison hemlock]
• Piniodeae - pine
• Piceoideae - spruce 
• Taxaceae - yew

Pruning pines

Pruning pines is different from pruning other trees and plants. Where most plants will sprout at the bud nearest a cut, pines only have one growing tip per branch. If this growing point is cut off, the branch will die. Pruning conifers is done before the branches actually form. As newly expanding buds, or candles, are seen, they can be allowed to grow, or they can be pinched back. Candles can be pinched back partially or completely. Candles are where the needles emerge. The bud is pinched back just as the needles begin to emerge. Where you pinch will dictate where new growth buds will form.

Pine needles

Looking closely at the needles of a conifer is one of the easiest ways of telling the different species apart. If the needles occur in bunches of two, three, or five, it is most likely a pine. If the needles occur singly, it is probably either a spruce or a fir. If that single needle rolls easily between the palms of your hand, it is spruce. [It actually has four sides, but you probably won’t be able to tell.] If the needle feels flat and does not roll easily, it is a fir.

Conifer pests and diseases

Bark beetles and their larva (roundhead borers) can cause significant damage to members of the pine family. Adelgids, aphids, spider mites, spittlebugs, conifer twig weevils, nematodes, and sawflies can also cause problems. The larva of several moths, including the clearwing, rusty tussock, Douglas fir tussock, spruce budworms, and the Douglas fir pitch moth all feed on conifers. These evergreens are all susceptible to canker diseases, root rot, crown rot, slime flux, and needle casts. Some of these pests can be captured with sticky barriers.

Few weeds come up as quickly and resiliently as common groundsel.

Also known as old-man-in-the-spring, this European annual weed prefers our cool, wet winter weather, dying off each summer, but it never fails to return each year. In fact, common groundsel is classified as a ruderal species, which means it is one of the first plants to start growing in disturbed soil.

Common groundsel description

Like other members of the sunflower family, common groundsel (Senecio vulgaris) features a sunny yellow flower. Akin to dandelion’s, mature seed heads transform into puffballs that fly on every breeze. The flowers of common groundsel are smaller than those of dandelions, and the green bracts have black tips. The plant has an upright growth, reaching up to 2 feet in height, but usually closer to 16 inches.

Rather than the lion’s tooth leaves seen on dandelion plants, common groundsel features pinnately lobed leaves (with matching loops and curves on either side), and may be toothed near the edges. Leaves are smaller near the top of the plant and may be covered with fine hairs. The leaves are sessile, which means they attach directly to the plant. The stems are hollow and the root system is a shallow taproot.

​Disease vector

If robbing nearby garden plants of sunlight and nutrients weren’t bad enough, common groundsel is also a carrier of disease pathogens (vector). It can host Cineraria leaf rust (Coleosporium tussilaginis), a fungal disease. It can also carry the fungus that causes black rot, another fungal disease that can affect citrus, chickpeas, cucurbits, such as cucumber or melon, tomatoes, and peas.

A toxic weed

While hailed as a medicinal plant, common groundsel contains chemicals, called pyrrolizidine alkaloids, that can make people and animals ill. Chronic exposure can cause irreparable liver damage. You’d have to eat an awful lot of it, but I avoid feeding it to my chickens, just to be on the safe side.

​Controlling common groundsel

Common groundsel is self-pollinating. Each plant can produce 1,700 seeds, and there can be  three generations per year. That ends up being a lot of weeds! The best way to control common groundsel is to prevent it from spreading in the first place. This means snatching seed heads any time they are seen and tossing them in the trash. Seedlings are far easier to pull than mature plants, so learn to recognize them and pull them out every time they are seen.

Heavy common groundsel infestations can be slowed or halted with sheet mulching. Follow these steps to successfully sheet mulch an area:

1. Remove and dispose of all seed heads.
2. Cut the plants off at ground level and leave them where they fall.
3. Water the area fully.
4. Cover the area completely with 3" to 4" of wood chips.

As with all weeds, this is an ongoing battle. Because these plants carry disease, it is better to be vigilant.

Good luck!

Before we start, let me first share a story from my early trials with edible flowers. My dear sister decided to marry an Australian sailor and asked me to make her wedding cake. It was a lovely tiered white cake with yellow borders. I decided to add some stunning yellow flowers I saw outside. My sister’s reaction of horror was not what I expected - until she explained that the Angel’s Trumpet flowers I used were extremely poisonous. Needless to say, the flowers and the frosting came off. So…

When in doubt, don’t

Before you go popping random blossoms in your mouth, you need to know that some flowers can make you sick, and others can kill you. If you are even remotely unsure about a plant, do not eat it. Sometimes there is a fine line between edible and inedible. For example, regular garden variety pea flowers and shoots are edible and delicious, while fragrant sweet peas (Lathyrus odoratus) are poisonous. Some varieties of daylilies are edible and others are not. The same is true for phlox and geraniums. Make sure you know what you have before tasting it.

Also, chemical sprays and car fume residue can be toxic, too. Chemical pesticides, herbicides, and insecticides should not be used on flowers that will be eaten. Never eat flowers from commercially grown plants, as there is no way to know for sure what has been applied to or used in growing these plants. Now that I have reminded you to be careful, let’s see just how many flowers in your garden are edible!

Edible herbs

All herb flowers are edible.
                              Basil, chives, cilantro, garlic, dill, lavender, marjoram, mint, oregano, rosemary, sage, savory, and thyme flowers can all be used to add an extra depth and a touch of color to many different dishes. You can also eat the flowers of anise hyssop, angelica, bee balm, burnet, chervil, fennel, ginger, and lemon verbena.

Edible flowers

There are a surprising number of edible flowers. All members of the viola family, which includes Johnny-jump-ups and pansies, and the dianthus family, or carnation fame, are edible.

• begonia, tuberous (Begonia x tuberosa) - citrusy leaves, stems, and flowers
• begonia, waxy (Begonia cucullata) - slightly bitter leaves and flowers
• borage (Borago officinalis) - cucumber flavor
• calendula (Calendula officinalis) - spicy or peppery petals; Poor Man’s Saffron
• carnations (Dianthus caryophyllus) - sweet, nutmeg-flavored petals
• chicory (Centaurea cyanus; Bachelor’s buttons) - sweet, clove-flavored blooms
• chrysanthemums (Chrysanthemum coronarium) - tangy, peppery petals; tangy new leaves
• clover (Trifolium sp.) - brightly colored new flowers are sweet, licorice-flavored
• crocus, autumn (Crocus sativus) - stigmas and styles are saffron; unsure about the edibility of petals, so don't
• dandelion (Taraxacum officinalis) - young flowers taste like honey; used to make wine
• daylily (Hemerocallis sp.; other varieties not edible) - petals taste like sweet lettuce; flowers can be stuffed; new shoots reminiscent of asparagus
• fuchsia (Fuchsia x hybrida) - brilliant, acidic blooms; berries are also edible
• gladiolus - remove anthers; flowers of nondescript flavor good for stuffing
• hibiscus (Hibiscus rosa-sinensis) - dried flowers for tea; cranberry-favored flower petals
• honeysuckle (Lonicera japonica) - honey-flavored flowers; berries are highly poisonous
• impatiens (Impatiens wallerana) - sweet flowers
• Johnny-jump-ups (Viola tricolor) - mild wintergreen flavor
• lilac (Syringa vulgaris) - varieties differ; lemony to bitter
• linden (Tilla spp.) - honey-flavored flowers; heavy consumption can cause heart problems
• marigold (Tagetes tenuifolia) - another Poor Man’s Saffron; citrusy
• nasturtium (Tropaeolum majus) - peppery flowers
• pansy (Viola x wittrockiana) - petals are mildly sweet; entire flowers taste like wintergreen
• peony (Paeonia lactiflora) - petals can be parboiled or used fresh; mildly sweet
• phlox, perennial (Phlox paniculata; NOT annual phlox) - spicy petals
• primrose (Primula vulgaris; Cowslip) - mild flavor; used in salads and to make wine
• roses - all rose flowers are edible; flavor depends on variety
• scented geraniums (Pelargonium sp.; NOT Citronelle variety) - lemony, spicy or citrusy
• sorrel (Rumex acetosa) - lemony flowers
• Sweet William
• tulip - tulip petals taste like sweet lettuce; some people are allergic; never eat the bulbs
• violets (Violata odorata) sweet, perfumed flavor

Edible fruit tree flowers

The flowers of many fruit and nut trees are also edible. Apple, apricot, peach, pear, and plum blossoms can be used to add color and a delicate complexity to many dishes. When using these flowers, be sure to only use the petals, and not the stamens or pistils. Because they contain low levels of cyanide, apple blossoms should be eaten in moderation. Citrus blossoms are very pungent and should be used sparingly. Leftovers can be added to floral arrangements, so that you can still enjoy the aroma.

Darkling beetle is the common name for all 20,000 species within the Tenebrionidae family. Some of the more famous California darklings include Blapstinus, Coelus., and Eleodes..

Darkling beetle behavior

These pests tend to walk with their heads down and their abdomens somewhat lifted. Very often, they will stand completely still, in a headstand position, if frightened. While not dangerous, they can squirt you with a nasty smelling secretion from that rear end that does not wash off easily. This behavior is what gives some darkling beetles the name Skunk Beetle or Stink Beetle, not to be mistaken with stinkbugs. For the most part, these pests only come out at night, but you may catch one running across the patio or lawn during daylight hours. Normally, they hide under dirt clods, fallen tree bark, rocks, boards, wood chips, and in other dark places during the day. Often, the only way you know you have a darkling beetle problem is because of the damage they cause.

​Darkling beetle damage

In addition to attacking seedlings at ground level, darkling beetles feed on the foliage of many garden plants, such as lettuce, chicory, cabbage, broccoli, and other brassicas, beans, melons, pumpkins, tomatoes, and squash. This feeding can be seen along leaf edges and on the underside of leaves. Darkling beetles also feed on the ‘netting’ (raised areas) of melons, the flowers of most cucurbits and pistachio, and on some fruit crops, such as figs.

Some species of darkling beetle also act as vectors for plant diseases and poultry parasites. Some darklings can also cause structural damage to insulation and wooden buildings. They are also attracted to poultry feed, but my guess is that the chickens make short work of that arrangement, as long as the unavailable feed is stored properly, in a metal container.

Darkling beetle control

Commercial farmers use insecticides to kill these pests. They also use a shallow ditch, filled with water, to block these pests from coming out of the weeds and into the fields. If you are an organic grower, as I am, you will have to use cultural controls. You can minimize darkling beetle damage organically when you:

• remove weeds and other plant debris from an area before planting
• speed up the breakdown of organic matter on and in the soil
• do not put seedlings out until they are 5 or 6 inches tall
• raise fruit off the ground with straw or hammocks
• eliminate dirt clods
• apply sticky tape barriers around fig trees
• allow planting beds to go fallow (unused) periodically
• avoid using alfalfa as a green manure in areas affected by darkling beetles (UCANR)

In 2015, a report published by The Coleopterists Bulletin warned that three non-native darkling beetles have been found in California and Nevada. Each of these species is somehow tied to ant or fire ant populations:

• Opatroides punctulatus Brullé, first discovered in the Sacramento area in 2003, now spreading rapidly throughout Nevada and California.
• Gondwanocrypticus platensis, a South American species of Crypticini that has spread widely in southern California
• Gonocephalum sericeum, an African native; this is the first sighting in the Western Hemisphere

I was unable to find any freely available photos, so you will have to track them down on your own. If you see any of these invasive beetles, please capture them and contact your local County Extension Office.

You may be surprised to learn that some people keep darkling beetles as pets.

Allelopathy is the scientific word for chemical warfare in the plant world.

There is plenty of New Age talk about ‘companion plants helping’ each other, but that is not true. Plants do not choose to help their neighbors. [We’ll get into the discussion about ‘plant intelligence' another day.] The truth is, life is a battle. Even in the garden.

Competition for resources

Most plant roots are constantly competing with neighboring plants for water and mineral nutrients. In the same way, most plants reach for as much sunlight as they can get, regardless of the needs of neighboring plants. That’s life. Its not a decision; its survival. Weeds compete with your garden plants by growing faster. Some plants use tendrils to climb other plants. And some plants use chemicals against neighboring plants and other organisms.

What is allelopathy?

Allelopathy [al-el-ah-path-ee] is a common way for plants to reduce competition in the immediate vicinity, and to reduce feeding by herbivores. Allelopathic plants actively discharge chemicals through their leaves, bark, and roots, as they decompose, and through other processes. These chemicals can stimulate or inhibit the germination, growth, development, reproduction, and survival of other plants and organisms. Autotoxicity is the flip side of allelopathy. In autotoxicity, plants generate chemicals to inhibit the growth of the same species in the vicinity. The chemicals used in allelopathy always impact other species of plants and organisms. These biochemicals are called allelochemicals.

​Allelochemicals

​Allelochemicals can interfere with another plant’s nutrient uptake, photosynthesis, pollen or seed germination, cell division, and even specific enzyme functions. These battles are being fought on the cellular and molecular levels! Because of these effects, allelochemicals are used in commercial agriculture as natural herbicides. For example, the lemon bottlebrush plant (Callistemon citrinus) produces an allelochemical called Leptospermone. Leptospermone is not strong enough on its own to be effective, but a synthetic version, nestorione, is. Nestorione is commonly used to control broadleaf weeds in corn, as well as the crabgrass in your lawn. Allelochemicals are also used as growth regulators, insecticides, and antimicrobial products. One advantage to using allelochemicals is that they tend to not have long term residual effects. Caffeine, and certain flavonoids, tannins, and phenols are all allelopathic chemicals.

Species distribution

Plants grow where their resource needs can be met. Because of this, allelopathy is an important player in species distribution and population density in the world and in your garden. In some cases, allelopathy gives weeds and invasive plants the upper hand. Nutsedge, garlic mustard (Alliaria petiolata), and spotted knapweed (Centaurea maculosa) all use allelopathy to beat out the competition. The allelochemicals used by garlic mustard have been shown to interfere with native tree roots and their mycorrhizal fungi, which help the trees gather mineral nutrients from the soil.

Allelopathy and incompatibility

Since some plants leave behind an allelopathic residue, it is a good idea to be aware of the potential for incompatibility when intercropping (succession planting), mulching, using green manure, planting catch crops, or when rotating crops. For example, decomposing straw has been shown to suppress weed growth, as well as reduce the number of pests and diseases found in an area, because of the allelochemicals contained in the straw. As it decomposes, it also improves soil structure and soil fertility. At the same time, decomposing straw temporarily increases the carbon-to-nitrogen ratio, so you may need to supplement the area with nitrogen.


Catch crops, planted to protect the soil from erosion between major crops, are an excellent way to protect your soil, but they also introduce allelochemicals that may interfere with the next crop. One sorghum-sudangrass hybrid (Sudex), in particular, can kill  50 to 75% mortality of your tomato, broccoli, and lettuce plants!

Allelopathic plants

Many common plants use allelochemicals. Black walnut is the most notorious, but the story isn’t (as is often the case) as simple as it is made out to be. Black walnut (Juglans nigra) produces several allelochemicals which are said to block everything from growing underneath. This is simply untrue. The chemicals involved, and the interactions, are far more complex than that. Onions, beets, squash, melons, carrots, parsnips, beans, yarrow, stonecrops, and corn can all be grown near a black walnut tree without any problems, according to the PennState Extension. At the same time, blackberries, raspberries, blueberries, asparagus, eggplant, peppers, potatoes, and tomatoes do not grow as well when planted near a black walnut tree, according to the University of Illinois Extension.

Allelopathy and agriculture
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Most of the research regarding allelopathy focuses on commercial agriculture. It tells us that rice, some Eucalyptus species, and the Tree of heaven (Ailanthus altissima) all use allelochemicals. It also demonstrates that rye mulch significantly reduces broadleaf weed growth, and that growing mung beans in a corn field reduces crop yield, while growing tobacco in the same corn field increases corn production.

Allelopathy in the garden

This is a highly complex issue that cannot be watered down very far before everyone is simply guessing. That being said, I have been able to glean the following useful information for the home gardener:

• Rotating eggplant with garlic makes positive uses of allelochemicals left in the soil. (NCBI)
• Broccoli residue can interfere with other brassica crops, so space out the rotations. (IFAS Extension)
• Pea mulch can suppress lettuce, wheat, or sorghum. (USDA)

If you suspect that two plants are incompatible, simply conduct an online search, using both plant names and the word allelopathy. If there is any research available, please let us know in the comments section!

Most of the ‘rules’ associated with allelopathy have been developed with large-scale agriculture in mind. They are diluted by all the other factors occurring in your garden and compost pile, so take it with a grain of salt.

This information is not going to stop me from composting my healthy pea plants, but it will make me more aware of my plant choices, when it comes to cover crops, crop rotation, and catch crop planting.

​Preventing woodpecker damage

The problem with woodpecker feeding is that the loss of sap may weaken a tree, and it creates a point of entry for other pests and pathogens. Unless the feeding is extensive, however, most trees can handle it without much of a problem. If the feeding becomes a problem, woodpeckers can be blocked by panels of lightweight sheet metal or 1/4-inch hardware cloth wrapped around the favored feeding areas.
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​​Woodpecker drilling can also cause structural damage to your home. This is especially true for trim boards, eaves, and wooden siding. Woodpeckers seem to prefer redwood and cedar. They are also attracted to plywood and other layered arrangements that create tiny spaces perfect for tasty insects.

​​All woodpeckers are protected under the Migratory Bird Treaty Act of 1918. But, you can use exclusionary measures to protect your home. The most effective method is to tightly stretch 3/4-inch bird netting over the eaves of your home, or to cover the side of a favored feeding/drumming wall.

​Research has shown that repellents and frightening devices are not effective. Urban myth claims that hanging nesting boxes and providing suet is one way to eliminate the risk of woodpecker damage. Research has shown that these provisions do not consistently reduce the problem and may actually attract even more woodpeckers into an area.

Benefits of woodpeckers

Before we try to ban these beautiful birds from our gardens, keep in mind that the nesting holes they create are often used by other native, cavity-nesting birds. Woodpeckers also remove a significant number of potentially damaging insects from our fruit and nut trees. Finally, we do not yet fully understand the value of biodiversity.

Ivory-billed woodpecker

While not a native of California, this magnificent bird of the Mississippi Delta deserves mention. The Ivory-billed woodpecker (Campephilus principalis) was/is believed to be extinct. The last confirmed sighting occurred in 1944. In 2005, video emerged that may have been of an Ivory-billed specimen. There is some debate about this, as it could also have been a slightly smaller, common Pileated woodpecker. The Cuban ivory-billed woodpecker has been considered extinct since 1987. Ivory-billed woodpeckers are/were very large. At 20” long, with a 30” wingspan, they must have been hard to miss. They were able to live 20 to 30 years, but Native Americans decided that the Ivory-billed woodpecker’s massive bone beak was a prized decoration, so the killing began. If you are ever lucky enough to hear the tell-tale double-knock of an Ivory-billed woodpecker, record it, photograph it, and contact the Audubon Society right away!

Leaves come in a variety of shapes. Having a firm grasp of the vocabulary associated with leaf shapes can help you to identify and talk about plants more effectively.

​This is a HUGE subject, so, grab yourself a beverage and get comfortable.

When describing leaf shape, some terms refer to the entire leaf, while others refer to specific parts of the leaf, such as the edge, tip, or base. Nearly all the terms are tied closely to the Latin word forms, so you are in luck if foreign language comes easily (or if you happen to already know Latin). Personally, I am not gifted in that particular area. Luckily for all of us, Latin is a pretty reliable language, when it comes to putting pieces of words together to make new words.

Some leaves are shaped like a heart, kidney, fan, arrowhead, or spear:

• Heart-shaped leaves, with a stem or petiole in the notch at the top of the heart, are cordate. If the stem attaches at pointed end, it is obcordate. [Beets]
• Kidney-shaped leaves are reniform.
• Fan-shaped, semicircular leaves are flabellate. [Ginkgo]
• Arrowhead-shaped leaves are sagittate. [Some spinach]
• Spear-shaped leaves with a flared base are hastate. Those that are equally pointed at both ends are lanceolate. Leaves with slightly less pointed leaves are linear. If the terminal end is wider than the stem end, it is oblanceolate. [Peaches]

Some leaves are shaped like a teardrop, while others look more like the silhouette of a violin, a spoon, a sickle, or a hand:

• Teardrop shaped leaves, with the stem at the pointed end are obovate. If the stem is attached at the rounded end, it is ovate.
• Violin-shaped leaves are pandurate. Banjo- or lyre-shaped leaves, with the widest part at the terminal end, are lyrate. [Oak]
• Spoon-shaped leaves are spatulate. [Sedum]
• Sickle-shaped leaves are falcate. [Eucalyptus]
• Hand-shaped leaves are palmate. If the hand looks webbed, it is palmately lobed. If the hand shape has incisions that are less than halfway to the petiole, it is palmatifid. If those incisions go more than halfway, it is palmatipartite. If the incision nearly touch the petiole, it is palmatisect. If the lobes all reach the petiole, it is pedate. [Currants]

The Latin of lobes

Some leaves have protrusions, called lobes, that can be rounded (like your earlobes) or pointed. Lobes can be arranged pinnately (in pairs) or palmately (like a hand). Lobes can be gently waving lines, they can be sharp incisions, or they can fall somewhere in between. These features are usually described as relative to the midrib line. Depending on the type of lobe a leaf might have, descriptive suffixes are added:

• Lobes that go less than halfway through the leaf to the midrib get “-tifid” put on the end of their name. This comes from the Latin word (findere) for cleaving.
• Lobes that go more than halfway through the leaf to the midrib get “-partite” put on the end of their name. This comes from the Latin word (partiri) for share, or portion.
• Lobe cuts that nearly touch the petiole get “-tisect” added to the end of the name. This comes form the Latin word (secare) for cut. [Artichoke]

All about the base

The way leaves attach to the rest of the plant can also provide clues for identification.

• If the leaf tissue tapers down the petiole, it is attenuate.
• If it has rounded mouse-ear shapes at the point of attachment, it is auriculate.
• If the base of the petiole or stem is triangular and wedge-shaped, it is cuneate.
• If the two sides of attachment are different, it is oblique.

Leaf arrangement math

The fraction of a circle used to arrange leaves around a stem is very species specific. You don’t have to be a math whiz to understand this stuff, either. Let me explain:

•    Imagine a pie cut into 360 very skinny slices
•     Each slice is a degree (°)
•     If you take 1/4 of the pie, you would have 90 slices or 90°  [360/4 = 90]
•     If you take 1/3 of the pie, you would have 120° [360/3 = 120]

Now look at leaf arrangement along and around a stem in the same way:

•     If a plant uses four leaves to go around a stem, each leaf is 90° apart
•     If a plant uses three leaves to go around a stem, each leaf is 120° apart

Are you with me? Hang in there! This stuff is amazing!

So, since leaves and stems are different sizes, and species have different sunlight needs, there are different fractions, or ratios of rotation, around a stem. For example, hazel leaves are arranged in 1/3 (or 120°) rotations, apricots use 2/5 rotations, sunflowers and pears use 3/8, and almonds use 5/13. This means that the leaves of an almond tree are positioned 5/13th of the pie apart. If you do the math, this works out to 38.5° between each leaf attachment, as you work your way up or down a stem.

This is where it gets really weird!

The fractions that describe leaf arrangement are almost always made with a Fibonacci number and its successor, as the numerator and denominator, respectively. Now, the number of steps taken for a leaf arrangement to work its way around a stem, before repeating the pattern, is called its gyres. A three leaf cycle of rotation has one gyre, while a five leaf cycle takes 2 gyres. The number of gyres ends up being the numerator in the Fibonacci number that describes the rotation! Holy spring bulbs, Birdman!

Whorls take this math to a whole new level

The rotation of successive whorls is nearly always one-half the angle between the leaves. For example, say you have a whorled leaf arrangement that uses three leaves. From what we calculated above, there would be 120° between each of those leaves, along the length of the stem. All the other whorls will be half that distance, or 60° apart from each other. I have no idea why.

Bottom line: whether leaves are alternate, opposite, whorled, basal, or distichous, the mathematics of leaf arrangement ends up providing each leaf with the optimal amount of sunlight.

[If you really love this stuff, check out Gray’s Botanical Textbook: Structural Botany (1879)]