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.  Young lambsquarters (6th Happiness CC BY-SA 3.0) Lambsquarters description
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. Lambsquarters control 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 (Rasbak CC BY-SA 3.0) 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.  Immature hairy bittercress fruit (Public Domain) 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. Vinegar makes for great pickles and salad dressings, but can it kill weeds? Let’s find out! We’ve all heard the story - spray your weeds with vinegar and they die. What a great idea! And so easy! But does it really work? First, let’s learn a little bit about vinegar.  Vinegar is not the weed killer you've heard about What is vinegar? You know it when you smell it or taste it. There is no mistaking the tang of vinegar, or the smell of decorating Easter eggs. Vinegar is a sour, acidic liquid made from fermented low-alcohol liquids, such as beer, wine, or cider. The acid in vinegar is called acetic acid. The vinegar you buy in the grocery store is 95% water and 5% acetic acid. When the concentration is 8% or higher, it must be labeled acetic acid. Some people call this higher concentration horticultural vinegar, but I find that label misleading. It is not vinegar. Vinegar is food, while acetic acid is a potentially dangerous chemical. The difference between the two matters.  Pickles (PhotoMIX) Pixabay Acetic acid as herbicide To be used as an herbicide, commercial agriculture uses a 20% concentration of acetic acid while wearing protective clothing. Acetic acid is a contact herbicide. This means it must come into contact with weeds to kill them. Acetic acid acts by dissolving cell walls, which allows fluids to leak out. This dries out the plant, potentially killing it. This method is more effective on younger plants and those with thinner skins. Tough, woody plants are more resilient, resulting in a burned appearance while remaining alive. Repeated treatments are often needed to kill off tenacious perennial weeds. Unsprayed parts are not affected. Plants accidentally sprayed are affected, as with any chemical overspray. You cannot buy acetic acid at the grocery store, but you might find it at a garden center. If you decide to use acetic acid to clear out some tough weeds, do not use your aluminum sprayer. Acetic acid will damage aluminum and iron surfaces. As with any pesticide, it should only be used on plants listed on the label, and it the manner described in the instructions. And be sure to wear eye protection and other personal protective equipment (PPE) when applying acetic acid.  Chemical Hazard symbol (The Navigators) Public Domain Vinegar as herbicide
If you spray weeds with household vinegar, the aboveground portion of the plants might dry up and die. Or, it might not. It will not affect the root system. By the time the vinegar filters through the soil to reach the roots, it will have gone through chemical changes that make it practically harmless. And what do weeds do when you kill off the aboveground portion? They come back, again and again, ready to produce thousands of little weed seeds. Of course, if you treat weeds repeatedly with vinegar, you will eventually force the plant to use up all the food stored in the root system, killing the plant. Probably. But honestly, it would have been simpler to just cut it off or pull it out in the first place. Let’s stop sharing these myths about vinegar in the garden and leave it in the kitchen where it belongs. That being said, if you have a bad sunburn. try gently wiping the affected area with a cloth soaked in vinegar. You might smell like a salad, but it won’t hurt anymore. I have no idea why. Cardboard and newspaper have long been touted as excellent tools to block weeds, protect raised beds, and in sheet mulching. We were wrong.  Cardboard (Pixabay) It is true that cardboard and newspaper block weeds. What we have found is that cardboard and newspaper do not always breakdown the way we expect. Without sufficient moisture, cardboard and newspaper can create durable barriers that attract a couple of serious pests. Cardboard and vermin It ends up that termites and voles love cardboard. By putting a layer of cardboard under your raised beds, you are putting out the vole and termite welcome mat. If you have voles, forget the cardboard and use sturdy hardware cloth instead. Cardboard and sheet mulching The use of cardboard and newspaper in sheet mulching restricts water and gas exchanges. This means nearby plants have a harder time getting the air and water they need. Depending on the soil structure and other conditions, the soil may become so dry that it is hydrophobic, leaving installed plants to die of thirst and weeds around the edges of the cardboard to enjoy the runoff it creates. Cardboard and newspaper can also slow evaporation and aeration, setting the stage for fungal disease and root rots. Newspaper, if kept moist, will break down. If it is not kept moist, it becomes a barrier. Sheet mulching only works successfully as a temporary weed control measure. Long term use of newspaper or cardboard actually creates more problems than it prevents. What to do if the cardboard is already in place? If you already have cardboard and newspaper in place, inspect it for signs of termites and voles. If signs of either are visible, remove it completely, bag it, and throw it in the trash. Then, inspect the soil underneath for signs of life. If the sublayer looks like hardpan or mud, you will need to treat it accordingly. Hardpan layers need organic material. Mud needs to dry out. Unless roots have grown into the cardboard layer, it is better to remove it completely. If it cannot be removed, poke holes in it and water it until it decomposes. Once you have corrected the problem, cover the area with a healthy layer of coarse wood chips and let it go fallow for a while. The wood chips will reduce weeds while feeding important soil microorganisms.  Brassica collar Cardboard still makes an excellent brassica collar or earwig trap. Beyond that, send it to the recycling center.
Geraniums are cheerful flowers, but cutleaf geraniums are pesky weeds.  Cutleaf geranium flower (Alvesgaspar) CC BY-SA 3.0
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 fruits (MurielBendel) CC BY-SA 4.0 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.  Common chickweed (Simon at Lawn Health) CC BY 2.0 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. Common chickweed 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.
Chickweed control
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). Glyphosate is an herbicide. It is the active ingredient in Roundup and other broadleaf weed and grass killers. Scientific research has shown that glyphosate may be partially responsible for the global die-off of honey bees. My soapbox Before we begin learning about this litigious herbicide, let me tell you from the gate that I do not use it in any form. I practice sustainable, integrated pest management (IPM) and organic gardening. The chemistry of glyphosate Glyphosate is a broad-spectrum, systemic herbicide, which means it is absorbed by and kills the plants it touches. It does this by blocking an enzyme pathway called the shikimic acid pathway. [It gets this unique name from the Japanese shikimi flower, which was part of the initial discovery in the 1800s.] When the shikimate pathway in many organisms is blocked, they die.  (USGS) Public Domain Glyphosate in the environment Glyphosate is the world’s most-used pesticide, with over 700,000 tons produced annually. As a substance, glyphosate molecules bind tightly to soil. While this means they are less likely to end up in groundwater as motor oil, it can cause a different type of pollution. Depending on soil type and weather conditions, glyphosate may remain in the soil for six months or more. Soil bacteria break down glyphosate, but I have to wonder about the chemicals those bacteria poop out afterward. Maybe it’s just me. Some studies have found that carrots and lettuce plants absorb glyphosate months after spraying. Many glyphosate products also contain other toxic ingredients. Glyphosate and GMOs Glyphosate use walks hand-in-hand with genetically modified plant development. GMOs are resistant to glyphosate and other weed-killing chemicals by design, allowing farmers to grow more food for our ever-increasing global population. It certainly has its appeal. It’s so simple—Aim, squirt, done. No more weeds. But at what cost? Glyphosate and overspray If you (or your neighbor) use a glyphosate product, be aware of the overspray risk. Since none of us is perfect, and breezes happen, these chemicals can travel on the wind to where they are not welcome. That delicate, well-loved exotic, handed down from your great-grandmother, is just as vulnerable to death by glyphosate as the dandelions. Also, since glyphosate indiscriminately kills all the plants it touches, many plants important to local biodiversity are being lost to this herbicide. We do not yet know the full extent of that domino effect. Glyphosate and bees Beekeepers have long suspected that glyphosate is partly responsible for the recent decline in global bee populations. [Did you know that China now must hand-pollinate their apple and pear trees because there are not enough bees?] Research from the University of Texas at Austin shows that glyphosate kills beneficial bacteria in a honey bee’s gut, making the bees more susceptible to infection. [Maybe we need to start feeding our bees probiotics? I’m guessing.] Glyphosate use Glyphosate first came on the market in 1974. It provided an easy way to kill weeds with just a squirt. Commercial farms, railroad companies, and city parks all use glyphosate. According to the National Pesticide Information Center, farmers use one form of glyphosate to regulate plant growth and ripen fruit. It’s convenient, but not what I want in or on my food. More than 750 products on American shelves contain glyphosate, including Roundup, Bonide KleenUp Grass and Weed Killer, and Kleeraway Grass & Weed Killer. According to the Environmental Working Group (EWG), glyphosate is also in many oat products on grocery store shelves. This organization has successfully gotten many companies to reduce the amount of glyphosates in our food. You can read more here. Drugwatch also has more information. The FDA is aware of glyphosate in our food but has failed to release its findings publicly. [Makes me wonder what we are paying taxes for...] Glyphosate may also be involved in Parkinson’s and Alzheimer’s diseases and may cause cancer. Herbicide safety As with any herbicide, always follow the package directions EXACTLY and COMPLETELY. It is not a time to be careless. You can harm other plants with overspray or expose yourself to dangerous chemicals. It can occur by breathing it in during the application process, eating or smoking after applying it, if you don’t wash your hands, or by touching plants still wet from the spray. If exposure occurs, follow the first aid directions on the product label. For more information about risks and treatments, contact the Poison Control Center at 1-800-222-1222. Pets are also susceptible to herbicide poisoning.  Remove weeds, roots and all (WikiHow) CC BY-NC-SA 3.0 Instead of using toxic chemicals to rid your garden and lawn of weeds, be industrious and pull them before they go to seed. While you’re out there, use it as a time to take a closer look at the other plants and soil and listen for the birds and insects that share your yard space.
Bottom line: glyphosate makes it possible to grow far more food, at least in the short term. But the long-term costs, in my opinion, far outweigh any convenience or benefits it may provide. Curly dock may sound like a fantastical marina attraction, but it’s actually an edible weed you probably already have growing nearby.  Curly dock (Pikist) Public Domain Curly dock (Rumex crispus) is also known as yellow dock or curled dock. There are several subspecies of curly dock, each adapted to distinct habitats. Curly dock is a perennial plant native to Western Asia and Europe. It is now found throughout the United States and Canada. Generally speaking, curly dock is considered an invasive weed. To make matters worse, curly dock is also a host plant of cutworms. Before you write off this sour salad green, keep in mind that it is also host to the ruddy copper butterfly, and it contains high levels of iron, vitamins A and C, and potassium. .jpg) Curly dock seed heads are a common sight in overgrazed pastures CC BY-SA 2.0 Eating curly dock Cousin to sorrel, and a member of the buckwheat family, curly dock leaves are larger and more bitter than its stylish relations. This bitterness is caused by oxalic acid. As such, only the young, tender leaves are harvested and eaten. You can also reduce the bitterness by boiling leaves in multiple changes of water, the same way some people cook collards. Mature leaves are generally too bitter to eat.
Curly dock description
Curly dock seedlings can be green or tinged with red. Wavy or curled leaves grow in a rosette, close to the ground, while flower stalks, or inflorescences, can reach 3 to 5 feet in height. Flowers are produced in clusters on these stalks. Fruits are triangular achenes, much like buckwheat. Curly dock seeds tend to catch on fur and sweaters, helping spread the species far and wide. Underground, curly dock features a large, forked yellow taproot. If you’s rather get rid of the curly dock in your garden, limit wet areas. Curly dock loves moisture. Also, be sure to cut off and dispose of seed heads before they mature. Eventually, you will reduce the curly dock population in your garden. If you happen to get stung by stinging nettles, rub a large curly dock leaf over the area to relieve some of the pain. You may be seeing large purple flowers popping up in your landscape each spring. Frequently considered weeds, the oyster plant offers delicious roots, shoots, and flowers.  Oyster plant with flower (Kate Russell) The oyster plant (Tragopogon porrifolius), also known as salsify, purple salsify, Jerusalem star, or goatsbeard, offers lovely spiked purple flowers each spring morning, tucking themselves discretely away by early afternoon. [The names goatsbeard and salsify are applied to other species, as well, so we will avoid using them here.] The oyster plant is a member of the sunflower family. Oyster plant description Oyster plants are a biennial wildflower/vegetable. Originally from the Mediterranean, this plant is now found around the globe. Oyster plants start out looking much like grass, with straight blade-like leaves. A central stalk emerges that can reach 4 feet in height, though they are normally half that height. If damaged or broken off, a milky white sap, or latex, is seen. The taproot looks much like a white carrot. Large purple flowers can be 2 inches across. Behind each flower head, you will see green spikes that are longer than the flower petals. These spikes are ligules of the ray flowers (petals). Flowers are both male and female. Pollination is performed by insects. These plants, similarly to dandelions, produce seeds that are actually dried fruits surrounding the seed. These seeds are known as achenes. Oyster plant seed heads look much like dandelion seed heads, only bigger.  Close-up of oyster plant achenes (Zeynel Cebeci) CC BY-SA 4.0 Edible roots, shoots, and flowers
This plant has been used for food for over 2,000 years. As a food, this plant has gained, lost, regained, and lost again its popularity. All parts of the oyster plant are edible. It is a mild, slightly oyster-tasting vegetable, hence the name. Once broken, the root tissue will become discolored and quickly spoil if not eaten soon after. This process can be slowed if the root is stored in water with a splash of vinegar. Young roots can be grated into salads, while older roots are cooked into soups and stews. Oyster plant latex can be used to make a chewing gum. Edible flowers can also be added to salads, and young floral shoots can be treated the same way you would use asparagus. Even the achenes can be sprouted and added to salads. Rather than yanking this plant out of your landscape as an unwanted weed, take advantage of its ability to grow without any help from us, savor its delicious taste, and enjoy the lovely blooms while they last. 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. .jpg) CA burclover (Ixitixel) CC BY-SA 3.0 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. .jpg) Green burclover burr (Harry Rose) CC BY 2.0 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 landscape 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.  Sowthistle (Pikist) Public Domain 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. .jpg) Annual sowthistle (Forest and Kim Starr) CC BY 2.0  Sowthistle seedling (Salicyna) CC BY-SA 4.0 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. Sowthistle control 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.  White clover (Forest & Kim Starr) CC BY 3.0 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.  Little hop clover (Wikipedia) CC BY-SA 3.0
Annual Clovers 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.  Yellow sweetclover (AnRo0002) Sweetclovers 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 Perennial clovers are often planted on purpose to reduce the need for nitrogen fertilizers. White clover (Trifolium repens) and strawberry clover (Trifolium fragiferum) both have the compound flower heads common to these clovers.  Strawberry clover (Christian Fischer) CC BY-SA 3.0
Beneficial clover
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. 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.  Buttercup oxalis plant (MathKnight and Zachi Evenor) CC BY 3.0 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 (carol) CC BY-SA 3.0 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:
As with all weeds, this is an ongoing battle. Because these plants carry disease, it is better to be vigilant. Good luck! Magenta Spreen may sound like a great steampunk name, but this edible annual weed is probably already in your garden!  Magenta spreen growing tips (Zoey Kroll) CC BY-SA 3.0 Also known as purple goosefoot, tree spinach, and giant lambsquarters, this local weed can reach 8 feet in height and takes practically no care. The fresh growing tips provide the best flavor (and they look amazing in a salad) but even the larger leaves can be steamed, the same way as spinach, and the seeds are edible, as well. Like rhubarb, spinach, parsley, and chives, magenta spreen contains relatively high levels of oxalic acid, but not enough to worry about.  'Chenopodium giganteum' The magenta spreen plant
Believed to have originated in India, magenta spreen made its way to China and then to other parts of the world, where it has long been a food plant. [In the 1500’s, magenta spreen lost out to spinach in the popularity race.] Cousin to chard, beets, and quinoa, magenta spreen (Chenopodium giganteum) is a chenopod that tastes like what you’d expect from a cross between spinach and asparagus. Like other chenopods, magenta spreen has triangular leaves, somewhat akin to a goose’s foot. Overall, the plants are green, but they feature iridescent, hot pink growing tips and new leaf edges. Magenta spreen can grow equally well in full sun or partial shade. If allowed to go to seed and flourish, it can be used as both an edible crop or as a green manure. It has no major pest or disease problems. How to grow magenta spreen If you live in relatively warm region, you have probably been pulling this plant out as a weed for years. Rather than ridding yourself of this visual and edible treat, simply let it grow! You don’t have to buy seeds, unless you’ve never seen it in your garden. In that case, plant seeds 1/2-inch deep in succession, starting in early spring or late summer. If plants bolt, let them. The seeds will provide you and your family with even more plants. They transplant easily, in case you don’t like where they start growing, or if you’d like to share with friends. 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.  Common dandelion flower (Greg Hume) CC BY-SA 3.0 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.  Dandelion in a lawn Dandelion plants 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 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. #/media/File:A_Taraxacum_Ruderalia_dandelion_clock.jpg) Dandelion cypsela (Richard Bartz) CC BY-SA 2.5 Dandelion latex
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. Dandelion roots 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. Dandelion control 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 landscape weeds: annual bluegrass. Annual bluegrass (Poa annua) is a cool season annual or biennial that appears each year with the first rains. This weed is a member of the grass family.  Annual bluegrass (Rasbak) CC BY-SA 3.0 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!)  Poison hemlock stem (King County) Public Domain 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.  Carrot leaf (left) and poison hemlock (right) image courtesy of World Carrot Museum 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. UPDATE:
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. I think I'll stay away anyway, 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.  Devil's apple 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. Creeping woodsorrel is a common lawn weed.  Creeping woodsorrel Creeping woodsorrel is a member of the Oxalis family, which gets its name because of its sour taste. If livestock eat too much woodsorrel, they can get oxalate poisoning. Personally, I just don’t like seeing it in my lawn. It tends to grow in tandem with clumping tall fescue grasses, stealing nutrients, sunlight, and prime real estate from more desirable turf grasses and ground cover. Know thy enemy Before you can eradicate creeping woodsorrel from your lawn, you need to understand how it lives, grows, and thrives. Creeping woodsorrel (Oxalis corniculata) is a perennial plant that grows close to the ground in all directions. This growth pattern is called prostrate (and don’t let me get started on what a pain in the rear getting rid of it can be!). Creeping woodsorrel is often mistaken for a type of clover, with its three heart-shaped leaves. These are actually leaflets, and they can be green to purple, or even red. Sometimes the leaves fold downward. The plants have small, 5-petaled yellow flowers, which tells us that this plant is a dicot. The seed pods tend to stick up, are cylindrical with tiny hairs. Each seed pod can hold 10 to 50 seeds, which translates into each plant producing over 5,000 seeds! If I actually liked these plants (which I don’t), I would be really impressed by the fact that seeds are ejected from the pods, sometimes landing as much as 10 feet away. Also, the seed hulls are rough, making them stick to socks, tools, pets, lawnmowers, pretty much anything. Clearly, these plants need to be dealt with sooner rather than later. Creeping woodsorrel seeds prefer temperatures between 60° and 80°F, but they grow year round in warmer regions. Temperatures over 97°F for 8 hours will halt this plant’s growth, but fall’s cooler weather is exactly what is needed for this plant to take over your lawn.
I attribute to increased worm population to cooler temperatures, more frequent watering, and the addition of aged compost spread lightly on top of the lawn as food. I also found that the soil structure, while still compacted, is much better than it was three years ago. (These things take time…) After breaking up the soil and fishing out the weeds, I mixed some aged compost into the pile and covered it with straw, leaving a bit of a trench around the edge (to prevent re-infestation). I will water the pile daily for a few days, just as I would with a new compost pile, to help break down the organic matter. Next, I will use cardboard or some other temporary barrier to keep other plants from moving in and plant some oregano. If it works, great. If it doesn’t, I’ll have that much more organic material in the soil that will feed whatever grass seed I decide on. I have decided to combine ridding my yard of creeping woodsorrel with an experiment in unique ground cover/lawn replacement. I noticed that the oregano in my herb garden is delightfully low growing, soft to the touch, and it smells great when you step on it! Be sure to check back and see how well it works! UPDATE: After one month passed, the new grass started coming in very nicely, without any creeping woodsorrel. I do have some rogue curly lettuce (left) and the oregano planted on purpose (right), but the creeping woodsorrel is currently a minority in this patch of lawn!  Bindweed (Convolvulus arvensis) is an insidious Eurasian garden and agricultural weed that is frequently mistaken for morning glory because the flowers look very similar. This invasive weed was first seen in California in 1884 and can now be found growing just about anywhere below 5,000 feet elevation. Bindweed can be particularly troublesome for beans, cereals, and potatoes, but it attacks many other crops, as well. Bindweed can carry viruses that carry tomato spotted wilt, vaccinium false bottom, and potato X disease.  Bindweed can be difficult to get rid of Bindweed identification
Bindweed is a hardy perennial that grows from rhizomes. It’s seed leaves (cotyledons) look square with a tiny notch at the top. Sprouts that emerge directly from rhizomes do not have cotyledons. Stems are flattened with a groove along the upper surface.True leaves are spade shaped and can be 1/2 -2 inches long. As leaves mature, they become lobed at the base. Stems can grow several feet in length and may trail on the ground or climb upright plants (such as my blueberry bushes). Bindweed control Since bindweed reproduces underground through rhizomes, as well as above ground by seed, it is especially difficult to control. The root system of bindweed can grow as deep as 20 feet! Roots able to bud are found as deep as 14 feet below the surface. The majority of bindweed roots are found in the top 2 feet of soil with most of the lateral roots in the top 12 inches. Due to its ability to overwinter without foliage, bindweed can persist in an area for up to 60 years. Herbicides may be effective as a suppressant but will not eliminate bindweed. Once bindweed has invaded an area, sheet mulching may be the only organic solution. Bindweed roots are able to penetrate most fabric, plastic and cardboard barriers, so the sheeting material must be exceptionally sturdy to be effective and it must remain in place for at least 3 years. Monitor for bindweed daily and pull seedlings as soon as you see them. Bindweed is less of a problem in shaded areas, so dense plantings can reduce bindweed’s success. Any word that ends with ‘-cide’ means death to something. In the case of herbicides, it means death to some or all plants that it contacts. Non-selective herbicides kill everything, while selective herbicides are slightly more choosy. Until the 20th century, weed management included cultural controls and old-fashioned elbow grease.  Man spraying herbicides in rice field (zefe wu) Pixabay Chemical warfare
Chemical warfare research from WWII discovered how synthetic plant hormones and other chemicals could kill many broadleaf plants. Several chemical reactions are going on when these chemicals are applied. Some herbicides work by halting cell production in the meristems (growth tips). Other chemicals starve plants by interfering with the production of amino acids or by halting photosynthesis. Using herbicides can lead to several problems, including:
Loss of biodiversity is a serious problem when it comes to herbicides. Nature’s balancing act is delicate. The effects of this chemical use are not fully understood. For example, Roundup (glyphosate) has decimated global Monarch butterfly populations. Other herbicides, like Paraquat, are so dangerous that only licensed professionals are supposed to have access. Long-term exposure to paraquat can kill you. You can read more about the health effects of paraquat here. Safer alternatives While chemical herbicides offer short-term convenience, there are many safer, sustainable options, including the following:
If you must apply chemicals in the garden, follow the package directions exactly. Confirm it is the correct herbicide for the site and the specific weeds. Apply too much, and the excess enters our water supply. You will also want to ensure that the weeds are in the correct life stage for the herbicide to be effective. If a chemical claims to be pre-emergent, it will attack germinating seeds. Post-emergent herbicides attack growing plants, and they work better on young plants. Post-emergent herbicides can be foliar (leaf absorption), root, contact, or systemic. Systemic herbicides are absorbed and spread throughout the plant. Be sure to read and follow product labels carefully. And dispose of the container properly. Better yet, practice sustainable, organic gardening. 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.  Dandelion (Greg Hume) CC BY-SA 3.0
Why get rid of weeds? Getting rid 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? Weed control 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. |
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