Garden Word of the Day
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Common lambsquarters (Chenopodium album) may be edible, but you probably don’t want it anywhere near your garden.
California goosefoot (Blitum californicum) is also known as lambsquarters, but is a close cousin to spinach and the subject of another post, another day.
Lambsquarters grows pretty much everywhere without any help from any of us. Sadly, this tenacious weed also plays host to several diseases.
Diseases of lambsquarters
These weeds are susceptible to a large number of plant diseases. The list of diseases commonly found on lambsquarter, and the crops they infect, include:
The green peach aphid, a serious disease-carrier, seems to prefer lambsquarters, which gives us yet another reason for pulling these weeds out as soon as they are seen.
Lambsquarters start out with tiny dull bluish oblong leaves. You may see a reddish purple on the underside. As leaves mature, they take on more of a toothed, lance shape. Leaves are covered with a white, powdery coating, especially when new. Stems are sometimes tinged red or purple. Flower clusters form much like the seed heads of millet and quinoa.
Pull them out. Dig them out. Don’t let them go to seed.
I have always called hairy bittercress the "fireworks weed” because of the way seeds seem to explode in every direction when the plant is touched. I was surprised to learn that this bitter herb is also edible. Let’s see what else we can find out about this persistent weed.
Hairy bittercress description
Hairy bittercress (Cardamine hirsuta) grows as either an annual or biennial and it is a member of the cabbage family. As such, it has tiny white, 4-petaled flowers. Before the flowers emerge, however, you will see young hairy bittercress plants as small rosettes of oval leaves, growing very close to the ground. This basal rosette continues to grow in circumference until tall stems emerge. These stems may be 3 to 9” long and that’s where the flowers come in. Those upright stems branch in several directions, each with their own flowers and resulting seeds.
How hairy bittercress grows
Found pretty much everywhere, hairy bittercress prefers moist soil, open ground, and freshly disturbed areas. Like other weeds, it grows rapidly, often having two generations each year. You may think they have disappeared during the heat of summer but the first autumn rain will let you know that they were merely waiting for wetter conditions. These plants have long taproots.
Hairy bittercress seeds are held in capsules, called siliquae. When the fruit within ripens, there are valves on the siliquae that create a tightly wound coil. That’s why, when you touch them, seeds explode in every direction. This method of seed dispersal is called ballochory.
Problems with hairy bittercress
Once hairy bittercress takes hold on your property, you will be dealing with it more and more each year, for better or worse. Because of its ability to fling seeds near and far, and grow quickly, hairy bittercress often finds its way into your garden on nursery plants. It is far simpler to put new plants into quarantine and monitor for weed growth right along with pests and diseases.
Before you shrug off this seemingly minor weed, you need to know that the real problem with hairy bittercress is the fact that it can host some nasty diseases. Specifically, tomato spotted wilt and cucumber vein yellowing can be carried into your garden on hairy bittercress. These diseases can have a huge impact on several of your crops, and not just tomatoes and cucumbers.
It is far easier to monitor the ground each spring and autumn for tiny rosettes and then use your long weeding tool to get under the taproot before it takes hold.
Geraniums are cheerful flowers, but cutleaf geraniums are pesky weeds.
Cutleaf geranium description
Cutleaf geraniums (Geranium dissectum) have disk-shaped, or orbicular, leaves with deep cuts, hence the name. The underside of leaves and stems may occasionally be red in color. Young plants grow in a rosette fashion. When growing in turf, these plants will stay prostrate, or low to the ground. In other locations, plants can reach 2-1/2 feet in height. The forked stem is hairy and those hairs, or trichomes, can emit fluids. Tiny pinkish-purple flowers have 5 petals and tend to appear in pairs, from March through October in California. Fruits are a 5-part carpel in the shape of a stork’s head and beak. As the seeds mature, each of the 5 parts curls back to release the seeds. Those seeds are round to oval and covered with tiny notches. If you pull up a cutleaf geranium, you will see a thin, shallow taproot with fibrous lateral roots.
Cutleaf geranium lifecycle
Cutleaf geranium can grow as either an annual or biennial plant, and is commonly found in disturbed ground and abandoned areas. Each plant can produce up to 150 seeds and those seeds can remain viable for 5 to 10 years.
Controlling cutleaf geranium
As with most the weeds, it is best to start controlling it early, before plants have a chance to go to seed. Hoeing is the best control.
Chickweed may sound like a 1970’s party girl, but the name actually refers to several common California winter weeds that can harbor pests and diseases.
While grown as poultry feed and ground cover, common chickweed provides food and shelter for lygus bugs, thrips, pale-banded darts or spotted-sided cutworms (Agnorisma badinodis), and dusky cutworms (Agrotis venerabilis). Common chickweed can also carry cucumber mosaic virus and spotted tomato wilt virus.
Succulent leaves grow opposite one another, and have a pointed tip. Common chickweed can reach 4 - 6” in height, but it generally grows as a short, dense mat, especially in lawns. The roots are fibrous and found near the surface. Stems tend to be weak, and plants produce white flowers and seed capsules at the same time. Common chickweeds plants have 5-petalled flowers, but each petal is split, to create the appearance of 10 petals.There are three species of chickweed found in California and they all germinate quickly and in abundance, under the cool, moist conditions common to California winters. Chickweed can complete its lifecycle in as little as 5 weeks, with each plant producing 800 seeds. If a single chickweed plant goes to seed in your garden or landscape, it can take 8 years before the seeds of that first plant are no longer viable. Be on the lookout for chickweed seedlings from January through the end of March.
Native to Europe, common chickweed (Stellaria media) is now found in many regions of North America and Asia. Also known as winterweed and chickenwort, common chickweed has been used as food and herbal remedy, though there is little or no scientific research to back up claims of common chickweed’s ability to provide cooling relief. Many people find the taste of this somewhat succulent annual too bitter to enjoy. Common chickweed contains high levels of iron, but the bitterness is caused by saponins, which can be toxic in large quantities.
Common chickweed is differentiated from its non-edible cousins by fine hairs found only along one side of the stem, whereas other, non-edible chickweeds have hairs all around the stem.
Mouse-ear chickweed (Cerastium fontanum ssp. vulgare) is taller than other forms of chickweed, reaching 4 - 8”. Hairy leaves grow opposite each other in a star-shaped pattern. This weed grows horizontally by putting out roots wherever the stem, which tends to fall over, touches the ground. Flowers are tiny and white, with 5 petals. The fruit capsules are brown and somewhat crescent-shaped.
Removing chickweed is difficult. Under cool, wet conditions, chickweed plants may send out roots at the nodes, which means every tiny piece of chickweed is a potential new plant. Thick layers of mulch and hand weeding, preferably before plants go to flower, are really the only organic methods of control. Heavy infestations can be managed with soil solarization. Unless you are feeding these weeds to your chickens, it is better to get them off your property completely, to avoid reseeding.
Ploughing or rototilling the area can reduce chickweed germination, but you may simply be trading one problem for another, as other weed seeds are brought closer to the surface. Maintaining a thick, vigorous lawn is another way to reduce the number of chickweed seedlings that make it to adulthood. Allowing your lawn to be taller than a putting green can reduce the amount of sunlight that reaches chickweed seedlings.
Before you completely write off common chickweed as undesirable, you need to know that it is also one of the preferred foods of the rare dainty sulphur moth (Nathalis iole).
How can a clover be a weed? Is it all bad? Let’s find out!
California burclover (Medicago polymorpha) is an invasive annual weed that looks a lot like other clovers. The name polymorpha refers to the fact that the burrs can be smooth or snaggish. As far as weeds go, this one isn’t entirely bad. Also known as burr medic, bur trefoil, and creeping burr, this weed actually has a lot going for it.
Cousin to white clover, black medic, and strawberry clover, California burclover is sometimes grown on purpose to feed livestock. Being an annual, however, it will leave bare patches in your lawn, come summer. Also, those little burrs can wad themselves up on your favorite sweater and they are not particularly fun to step on barefooted. While some burrs are smooth, most of them feature rows of tiny velcro-like hooks that snag. Like other weeds, the best time to pull them out is when they are small and young, before they go to seed.
California burclover identification
Seed leaves (cotyledons) are oblong. The first set of true leaves are rounded. Mature burclover leaves look like they fold in the middle and are three round leaflets. They may have reddish midveins and toothed margins. Stems can reach 2 feet long and tend to trail, but may be upright, and they break easily. Small yellow flowers form in clusters at the end of stems. The seed pod is either smooth or a prickly burr that sticks to pet paws and fur, shoes, clothes, and enough other things that this pesky weed can easily be brought into your garden or landscape after a stroll around the block. These burrs look as though they are twisted on themselves. They start out green and then turn brown and hard. While these prickly burrs can get tangled in your pet’s fur, they are not the “stinging” “life threatening” weeds sensationalist articles claim. We will leave those claims to the foxtails.
The good side of burclover
In addition to being grown as livestock and chicken food, California burclover is also used as a ground cover, winter erosion control, green manure, and in soil restoration. A drought tolerant legume that thrives on slightly alkaline soil, burclover requires very little water and it grows rapidly into a dense vegetative cover that adds nitrogen to the soil. A single acre of burclover can produce 8300 lbs. of biomass in a single season! In many areas of the world, burclover is rotated in pastures with cereal grains for a continuous supply of healthy food for livestock. If you were/are a farmer growing hay for livestock, adding burclover to your oats and wheat can increase production by 3 to 5 times.
But you probably see burclover as a weed in your lawn, as I do. Now that I know burclover is also a nutritious legume, I will feel better about feeding those weeds to my chickens.
Annual sowthistle is a common California weed that plays host to several garden pests.
While all weeds compete with your garden and landscape plants for sunlight, water, and nutrients, some weeds also carry diseases or provide habitat for pests. The annual sowthistle is one of those weeds.
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.
Pests carried on sowthistle
Pests carried on sowthistle include lettuce aphids (Nasanovia ribis-nigri), lettuce root aphids (Pemphigus busarius), green peach aphids (Myzus persicae), and nematodes. Sowthistle should also be considered a vector of several different plant viruses. Pulling these weeds from your garden can break the disease triangle for many of these viruses, reducing or eliminating the need for more extensive treatments.
Pulling up seedlings as soon as they are seen is the easiest control. Unlike many other weeds, sowthistle does not regrow from root fragments. Since sowthistle only reproduces by seeds blown on the wind, preventing those seed heads from forming can significantly reduce your workload in the one run.
Luckily, sowthistles are easy to pull up.
Four-leaf clovers may bring good luck, but some clovers can be a real pain.
The word clover actually refers to three different genera of plants: Trifolium, Medicago, and Melilotus. There are over 300 species of clover and they are found throughout the Northern Hemisphere and occasionally in South America and Africa. Depending on who you ask, clovers can be beneficial ground covers or pesky weeds.
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.
Annual Clovers grow mostly in a prostrate manner from a single taproot. They feature tiny yellow flowers. CA burclover (Medicago polymorpha) and black medic (Medicago lupulina) are turfgrass weeds, while little hop clover, also known as lesser trefoil or shamrock clover (Trifolium dubium) is frequently added to turfgrass mixtures.
Sweetclovers are upright annuals or biennials that grow from 2 to 5 feet tall. White sweet clover (Melilotus alba) and yellow sweetclover (Melilotus officinalis) often turn up in ornamental plantings.
Perennial clovers are often planted on purpose to reduce the need for nitrogen fertilizers. White clover (Trifolium repent) and strawberry clover (Trifolium fragiferum) both have the compound flower heads common to these clovers.
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.
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.
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 San Jose, California, 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.
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.
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.
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:
As with all weeds, this is an ongoing battle. Because these plants carry disease, it is better to be vigilant.
Sunny yellow flowers, toothed leaves, and a seed head that simply begs to be blown are all characteristic of the weed commonly known as dandelion.
The word dandelion, which means lion’s tooth, actually refers to several different plants in the sunflower family. Native to Europe and Asia, dandelions have been following humanity across the globe, taking advantage of soil disturbed by agriculture, fires, and construction. This makes them a ruderal species. Ruderal species are the first plants to colonize disturbed land.
Bane of lawns everywhere, the common dandelion (Taraxacum officinale) was brought to North America in the 1600s to be used as both food and medicine. The species name officinale refers to an early English word meaning medicinal.
Cousin to lettuce and chicory, dandelions are easy to recognize, with their low-growing (basal) rosette of toothed leaves and bright yellow or orange composite flowers. Composite flowers are actually made up of several florets, clustered together. Dandelion florets reflect ultraviolet light, which attracts many beneficial insects, looking for nectar and pollen. Surprisingly, dandelions do not need to be pollinated to set seed. Instead, seeds are produced asexually, in a process called apomixis. As a result, all offspring are identical to the parent plant. Besides the floral stem, dandelions are acaulescent, which means they appear to not have any structural stems.
Dandelion flowers open each morning and then close each night, in a behavior called nyctinasty. Each plant can produce up to ten floral stems. The cuplike structure seen at the base of each dandelion floret is called a calyculus. Once the flower has matured, it will begin to dry out. After the dried petals and stamens fall off, specialized leaves, called bracts, curve backwards, exposing the seed ball. Each stem produces a single seed ball. These seed balls are commonly called blowballs or clocks. The seeds we see are actually a special type of fruit, called a cypsela. The feathery bristles that act like a sail are called pappi (pappus, singular). The hollow flower stem contains a bitter latex used to defend against herbivores.
Latex is used to make rubber. While most of the latex used to make rubber today comes from the rubber tree (Hevea brasiliensis), you can make your own rubber from dandelion latex! You can make an elastic band simply by coating your finger with dandelion latex, allowing it to dry, and then rolling the latex off your finger. Voilà! You can also make a bouncing ball or waterproof fabric out of dandelion latex. [Did you know that a man named Charles Macintosh figured out how to smear latex between two pieces of fabric to make waterproof fabric? That’s why raincoats are often called macintoshes!] When dandelion latex dries, it stays sticky until it cures. Curing latex involves applying heat and sulfur. The curing process removes the stickiness. Dandelion rubber is stiff in cold temperatures and supple when it is warm. Only Russian dandelions make a latex that is strong enough to be used commercially. [I just learned that one company is researching the use of Russian dandelion latex to make automobile tires!]
Dandelions as food
All parts of the dandelion plant are edible, but you may want to harvest the newest leaves to avoid some of the plant’s bitterness. Eaten the same way as spinach, dandelion greens are packed with good nutrition, including high levels of vitamins A, B, C, and D, according to the University of Maryland Medical Center. Dandelions also contain a lot of iron, calcium, potassium, and zinc. Young dandelion roots can be peeled and eaten. They are said to taste like turnips, but I haven’t tried them yet. The roots can also be roasted and used as a coffee substitute. The flowers are also edible. They can be sautéed in oil with a little garlic and they can be used to make dandelion wine.
Dandelions as medicine
Traditionally, dandelion has been used to treat infections, digestive problems, as a mild laxative, and to stimulate the appetite. Dandelion leaf tea was said to “purify the blood” and the milky latex was used as both mosquito repellent and wart remover, though I couldn’t find any scientific proof to back up any of these claims. According to WebMD, no research has demonstrated any verifiable medicinal use of dandelion, though it does contain chemicals that decrease swelling and increase urine production.
These herbaceous perennials have taproots that are strong enough to counteract compacted soil. Hell, they can break through concrete! While dandelion roots are typically only 6 to 18 inches deep, some specimens go 10 to 15 feet deep! Dandelion plants can live for up to 10 years and reach 20 inches in diameter.
I used to try to eliminate dandelions from my lawn, despite my love for their bright yellow flowers and the irresistible seed heads. I finally decided to try putting the plants to work for me in my heavy clay soil. While mulching and growing green manures and cover crops has significantly reduced soil compaction on my property, I have a theory about dandelion taproots. It goes something like this: Since dandelion taproots are strong enough to break asphalt, I allow them to grow, regularly removing the greens (for salads and as a treat for my chickens), before flowers emerge. My theory is that the dandelion taproots will dig down into my compacted soil, bringing microorganisms with them, to create healthier soil. Even if it doesn’t work, I still get pretty flowers and edible greens. Maybe I’ll even try making dandelion wine, one of these days. If my theory is wrong and I end up with a severe problem with dandelions and other, similarly growing weeds, I make have to resort to other control measures.
If you really must get rid of the dandelions in your lawn, it will take consistent effort on your part. As you already know, those seeds can blow in on the wind from miles away. This battle never ends. While herbicides will certainly kill individual dandelions, those same chemicals can be toxic to other living things, such as us, and our pets. Maintaining a healthy lawn and removing plants as soon as they are seen is the best control method. Cutting off young plants at ground level, a practice called grubbing, is effective only if you are diligent. Crabgrass preemergent herbicides advertised as effective against dandelions do not prevent seeds from germinating.
Love ‘em or hate ‘em, dandelions have been around for 30 million years, and they are here to stay.
You may as well make the most out of these common weeds.
There’s the toe tappin’, git yer yee-haw on sort of bluegrass, and then there’s one of the most common California weeds: annual bluegrass.
Annual bluegrass (Poa annua) is a cool season annual or biennial that appears in San Jose, California, with the first rains. This weed is a member of the grass family.
Annual bluegrass identification
Annual bluegrass starts out looking like many lawn grass varieties, Kentucky bluegrass, in particular, except that it has shallower roots, seeds more rapidly, and it is a lighter shade of green. To the untrained eye, grasses are grasses. A yellowish to dark green blade emerges, a couple more blades show up, and then a flowering stalk comes out of the center, hosting a flower cluster that spreads this problem far and wide. To identify annual bluegrass, you will need to take a closer look at the blade. The tip is said to look like the bow of a boat. The mid-blade may have a crinkly section. And the collar, where the blade meets the sheath (or stem), has a slightly pointed, jagged tip. Annual bluegrass grows low to the ground, spreading in clumps that can be 3 to 12 inches tall. The root system is fibrous and you may even see roots emerging from the lower portion of the aboveground stem. Flowers may be seen December through July. Flower heads are egg-shaped or triangular, and can be bright green or purplish.
Why do you care?
At first glance, this weed may look like an acceptable addition to your lawn. It’s a grass. It’s green. It grows like crazy. So, why would we consider this particular grass a weed? Well, first, it turns brown and dies back as soon as the top of the soil gets dry, leaving ugly, dead patches in your lawn. Those patches then erode or create homes for other weeds. In the garden, this weed robs your edibles of water and nutrients needed to stay healthy and produce an abundant harvest.
Annual bluegrass control
Watering your lawn deeply and infrequently will make life more difficult for annual bluegrass. It will also make your lawn healthier and more drought tolerant. Also, maintaining your lawn at a height of 3 or 4 inches will shade out this weed. Individual clumps can be dug out as soon as they are seen. I feed them to my chickens, but you can add them to the compost pile, as long as they haven’t gone to seed. Heavy infestations can be treated with pre-emergence herbicides in late summer or early fall, if you use that sort of thing. [I don’t.]
If annual bluegrass is seen in the garden, pull it out before it has a chance to go to seed and spread. You can also lay 6 to 8 sheets of wet newspaper over unplanted areas of the garden and then cover the paper with 2 to 3 inches of organic mulch, such as pine needles, straw, or aged compost. The wet newspaper acts like a weed barrier and the mulch feeds the soil while interfering with weed seed development.
Some plants are out to kill you and hemlock is one of them.
Poison hemlock, also known as poison parsley and California fern, is not related to hemlock trees, but it does look an awful lot like a carrot gone to seed.
Poison hemlock (Conium maculatum) is a member of the Umbrelliferae (or Apiacea) family, making it cousin to parsley, celery, parsnip, dill, cumin, fennel, and carrot. All of these herbaceous, biennial plants have flower structures that look like flattened umbrellas. Native to Europe, poison hemlock was brought to the U.S. in the 1800s as an ornamental and is now found throughout the country. Whoops.
A deadly fern
All parts of the poison hemlock plant are extremely poisonous. In 399 B.C., Socrates was found guilty of heresy and corrupting the minds of Athenian youth. For this, he was sentenced to death by drinking poison hemlock. The alkaloids found within poison hemlock cause paralysis of several organs, including the respiratory system, usually within 2 or 3 hours. Eating only a tiny bit of the toxins found in poison hemlock can cause death. People with skin sensitivities may experience irritation by brushing against the plant, but eating it CAN kill you.
Poison hemlock identification
Poison hemlock looks a lot like both domestic and wild carrots, or Queen Anne’s Lace. Unlike Queen Anne’s Lace (Daucus carota) and domestic carrots, which have hairy stems and leaves, the leaves and stems of poison hemlock are smooth. Plants can reach 10 feet in height. The root, which looks a lot like a carrot, is pale yellow or white. It often smells like a mousy parsnip. Purple or red streaks or spots on slender, hollow stems is a clear sign that you are looking at poison hemlock. Stems may also have a white bloom that is easy to rub off. (Just be sure to wash your hands thoroughly afterwards!)
There are many branches and the plant often has a wispy, feathery appearance. Leaves are triangular and divided into many fractal iterations of the overall shape. Small, white, clustered flowers normally appear April through July. For comparison, carrot flowers tend to be more pink, but not always. Poison hemlock seeds are held within gray, ribbed fruit, in pairs.
Poison hemlock population explosion
Poison hemlock often grows alongside creeks and in locations with shade and moist soil. Many areas, including Cupertino’s McClellan Ranch Park and the Trukee River, see population booms after wet winters. Seeds (of many different plants) that had been dormant for several years use that moisture to germinate, rushing to reproduce. Just don't be fooled by this deadly plant's delicate appearance.
Just as the “leaves of three, let it be” rhyme has provided years of protection from poison ivy, try embedding this rhyme in your brain to help you stay away from poison hemlock:
Stems so smooth with purple streaks
Flowers white, a deadly stink
If you suspect poisoning from this plant, call Poison Control immediately at 1-800-222-1222. A quick response can save a life.
Thanks to John, curator at the Carrot Museum, I have learned that poison hemlock, for all its toxicity, is also used as a medicine. Seeds, roots, and leaves, when handled properly, can be used to treat respiratory conditions, such as whooping cough, asthma, and bronchitis. Poison hemlock has also been used to treat painful joints, to counteract anxiety and epilepsy, and to reverse strychnine poisoning.
Devil’s apple is a poisonous weed from Africa.
Called Devil’s apple because of its toxic yellow fruit, Solanum linnaeanum made an appearance under my almond tree. When I went to pull it out, I discovered its substantial thorns.
Considered an invasive in Australia, Devil’s apple has been getting a lot of press lately. Dramatic statements declare that Solanum linnaeanum can cure skin cancer. And I could not find a single piece of scientific evidence to back up those claims. Hmmm. Yet another snake oil salesman… Why do we tolerate all those untruths?
The truth about Devil’s apple is interesting enough on its own, so let’s learn what we can.
Devil’s apple is a member of the nightshade family, along with potatoes, tomatoes, and eggplants. These shrubs can reach 6 feet in height, and those spines can be 1/2 an inch long. I sure wouldn’t want to fall into one of those bushes!
Also known as apple of Sodom, Afghan thistle, and Dead Sea apple, this weed invades pastures, agricultural fields, roadsides, and now, my yard.
The yellow berries start out as a star-shaped, 5-petaled purple flower, the way most nightshades do, but then they start looking more like a small apple, hence the name. The fruit changes from white or green to bright yellow and it contains toxic alkaloids. DO NOT EAT THEM!!!
Devil’s apple is also host to the Malaysian Fruit Fly, which earns it a listing in the California Code of Regulations, as part of the state’s emergency eradication program. Other than that reference, I have not been able to find any mention of the plant in California, so I have submitted an information request to local Master Gardeners and UC Davis to see if this is a new weed in the Bay Area. I’ll keep you posted.
For the time being, if you see one of these in your garden or landscape, dig it out.
Warm temperatures and moist soil are all it takes to help weeds invade your garden, lawn, and landscape. Fighting weeds is a constant battle, but it is much easier while they are young and vulnerable.
Why get rid of weeds?
Getting ride of weeds is work, so why bother? There are many reasons for getting rid of weeds:
So, getting rid of weeds helps your plants stay healthy. Most of the time.
Benefits provided by weeds
Before trying to rip out every weed on your property, you may be surprised (and relieved) to learn, as I was, that some weeds actually provide benefits. Because they grow and go to seed so fast, weeds reduce erosion and the loss of top soil. Weeds can also be used to support soil microorganisms and to add organic material back into the soil. Weeds absorb carbon, keeping it out of the atmosphere, increase biodiversity, and provide food and shelter for native insects and animals. In some cases, weeds act as trap crops, luring pests away from favorite plants.
Looking at the sunny dandelion in this new light, we see it has a taproot that grows in even the most compacted soil, provides nectar and pollen for beneficial insects, new greens can be used in a salad, and flowers can be used to make wine! So, not all weeds are bad. But most of them are not what we want in our gardens.
What is a weed?
Before we start learning about some of the more common weeds, let’s be clear about what a weed is and what it isn’t. According to Gallagher, “If you pull it out and it grows back, it’s a weed.” I’ve always said, "A weed is a plant that grows after you try to kill it.” So, how do we get rid of unwanted weeds?
Weeds are some tenacious opponents. They have evolved to go to seed only days after emerging from the soil. Their stems and roots tend to be brittle, so part of them is left behind to continue after you try to pull them out. There are only two ways to get rid of weeds: the Hard Way and the Hard Way.
Which of these weeds cause problems in your garden?
Annual sowthistle (Sonchus oleraceus) Like dandelions, sowthistle seeds travel on the wind, so they will always be back. Learn to recognize these weeds while they are young, before they go to seed.
Burning nettle (Urtica urens) and stinging nettle (U. dioica), have tiny hairs along the stem that sting for several minutes and can itch for hours.
Common lambsquarters (Chenopodium album) may be edible, but these weeds can also carry beet curly top, potato viruses M, S, and X, tomato ringspot, and several mosaic diseases of alfalfa, barley, beans, beets, cucumber, eggplant, hops, lettuce, squash, and watermelons.
Field bindweed (Convolvulus arvensis) may have pretty flowers, but that root system can down 20 feet or more! Also, bindweed frequently plays host to viruses that impact beans, potatoes and cereals, such as tomato spotted wilt, vaccinium false bottom, and potato X disease. If you discover bindweed in the garden, your best bet is to monitor the area frequently and pull new growth as soon as it is seen. You can also use sheet mulching.
Pigweeds (Amaranthus spp.) provide overwintering sites for disease-ridden green peach aphids and beet armyworms, which negatively impact beans, buckwheat, celery, cilantro, citrus, cole crops, cucurbits, lettuces, parsley, peppers, strawberries, and tomatoes.
Spotted spurge (Euphorbia maculata) is a common weed that can reach a surprisingly large size. Mature plants can be several feet in diameter!
Of course, poison ivy, poison hemlock, and crabgrasses are commonly referred to as weeds, as are the many invasive plants being installed haphazardly. Kudzu, ice plant, purple nutsedge, and English ivy are wreaking havoc on local environments wherever they occur. Once established, it is very difficult to get rid of them.
If you are unsure about a potential weed in your garden, post pictures in the Comments section and we can work together to identify it.
You can grow a surprising amount of food in your own yard. Ask me how!
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