Age-Old Wisdom meets Modern Tools
Identifying and Controlling Common Weeds
No one likes to talk about weeds, but if you’re growing vegetables, fruit, herbs, or flowers, it’s important to identify and control the unwanted plants. Here are 13 of the most common weeds found in gardens and lawns—with weed identification pictures and tips on how to manage their growth.
What is a Weed?
A weed is simply a plant growing where it is not wanted—usually in competition with cultivated plants. For example, if you are intending to grow strawberries, you don’t want other plants (weeds) taking over your patch.
Understand how different plants grow and spread. A handful of weeds are naturally strong competitors; those weeds that can best compete always tend to dominate.
Of the approximately 250,000 species of plants worldwide, only about 3% behave as weeds that we don’t want in cultivated areas. These weeds have many traits in common, including:
- Abundant seed productivity—sometimes tens of thousands of seeds per plant.
- Rapid population establishment and spread.
- Long-term survival—seeds go dormant but then sprout just as soon as conditions are right.
These weeds are troublesome in many ways. Primarily, they reduce crop yield by competing for water, light, soil nutrients, and space. Some produce chemical substances which are toxic to crop plants (and often animals and humans).
“Weeds” aren’t inherently bad, though! Many weeds stabilize the soil and add organic matter. Some are edible to humans and provide habitat and food for wildlife, too. See “Eating Weeds: Why Not?”
So, there is a balance. To the agriculturist, the weeds that interfere with cultivated crops do need to be controlled, in an economical, practical and safe way, in order to produce food, feed, and fiber for humans and animals.
Top 5 Weed Control Tips
1. Never let ‘em set seed!
This is the #1 rule with weeds. Some varieties produce tens of thousands of seeds from a single plant, multiplying your weed control problems for years to come. So make certain you remove weeds around your home before they flower and produce seeds. Pigweed, purslane, Shepherd’s purse, chickweed, and lambsquarters are examples. Their seeds are very small and light enough to be blown by the wind over short distances, spreading profusely and often surviving for decades in the soil.
Remember that it may take a few years to get weed-free. Seeds of most annual weedy grasses die after two or three years, but some broadleaf weed seeds can last much longer. On average, though, the bulk of your weed seeds will be depleted in about five years if no additional seeds are added. That means diligence is the key.
For further weed suppression throughout the growing season, apply two to three inches of mulch or use landscape fabric or black plastic. Mulch not only blocks weed seeds from sunlight so they do not germinate, but also promotes better water retention, provides needed nutrients as it decomposes over time, and moderates soil temperatures. If you mow or blow leaves in the fall, be sure to get a shredder (like this one from Echo) to turn those leaves into garden mulch—and save yourself the costs of buying bags of mulch.
3. Turn to tools.
A garden hoe, tiller or even hand-weeding can work, especially if the space you’re tending is fairly small. And keep your tools (garden hoe, spade, mower, tiller) clean to keep from spreading weed seeds or plant parts that you encounter. Tillers like this one from Echo is ideal for aerating soil and keeping flower and plant beds weed-free, turning what can be a difficult job into easy, productive work.
4. Establish a perimeter.
Pay special attention to the area adjoining your flower bed, garden, natural area or lawn and establish a weed-free perimeter. Mow or mulch the area or pull or dig up weeds as they emerge. You’ll help to reduce the number of new weed seeds in the area you want to protect. Also, a good trimmer (like this one from Echo) can make it easier to reach weeds along garden beds, posts, and tight spots.
5. Pay special attention to perennial weeds.
When you deal with perennials, you need dig up any roots, underground tubers and rhizomes without leaving fragments behind. New weeds can grow from any pieces that break off and remain in the soil. It does also help to cut off the emerged green part of the weed with your hoe or mower—repeating the process quickly each time it regrows. Without leaves needed for photosynthesis, the underground plant parts will become weakened and may eventually die.
With these techniques, you’ll soon find that you won’t spend much time weeding the following years!
13 Common Weeds
Some of the below weeds are noxious and invasive, while others have more beneficial uses (and could even be harvested), but all are rated as the most troublesome weeds that compete with vegetables, fruits, and crops (source: WSSA).
1. Bindweed (Perennial Morning Glory)
Field bindweed (Convolvulus arvensis) is a hardy perennial vine that has been given many names, including perennial or wild morning-glory, creeping jenny, sheepbine, cornbind, and bellbine.
Bindweed is NOT the same as the ornamental annual morning-glory (in the genus Ipomea) which has a larger (2-inch wide) and more showy flower that can be white to blue or purple; it also has a thicker stem that is sometimes hairy and heart-shaped leaves that are 1 ½ inches wide and 2 inches or more long. The two species are easy to distinguish from each other.
An invasive from Eurasia, field bindweed is one of the most persistent and difficult to control weeds. It spreads from an extensive rootstock and from seed. And its roots are found to depths of 14 feet! Lateral roots becoming a secondary vertical root. A single field bindweed plant can spread radially more than 10 feet in a growing season. This extensive underground network allows for overwintering without foliage, and it can persist for many years in the soil.
Bindweed sprouts in late spring and can be seen throughout the summer. Though the plant’s flowers are attractive, field bindweed can become a big problem in warm weather, when they spread ruthlessly.
Image: Bindweed seedling
Unfortunately, tilling and cultivation seems to aide bindweed spread. Fragments of vertical roots and rhizomes as short as 2 inches can form new plants! Field bindweed also is very drought tolerant and once established is difficult to control even with herbicides.
The best control is, as with most weeds, is prevention or early intervention. Seedlings of field bindweed must be removed before they become perennial plants. However, this need to be done when they’re young—about 3 to 4 weeks after germination. After that, perennial buds are formed, and successful control is much more difficult.
Bindweed can grow through many mulches so you need to use landscape fabrics such as polypropylene and polyester or mulches such as black plastic or cardboard but also ensure that the edges of the covering overlap so that the bindweed stems can’t find their way into the light. If holes are made in the fabric or plastic for plants, bindweed will grow through these holes. A landscape fabric placed over soil then covered with bark or other plant-derived product (e.g., organic matter) or rock will likely keep field bindweed from emerging. It might take more than 3 years of light exclusion before the bindweed dies. Once landscape fabric or other mulch is removed, new bindweed plants might germinate from seed in the soil; be sure to monitor the site for new seedlings.
Lambsquarters. Photo by Michigan State University.
According to the Weed Science Society of America (WSSA), lambsquarters ranks as the most common weed in gardens.
Common lambsquarters is an annual broadleaf weed that is widely distributed across the northern half of the United States and southern Canada. So it’s not surprising that lambsquarters is a problem in gardens with sugar beets, vegetable crops and pulse crops, such as dry edible beans, lentils and chickpeas.
Lambsquarters is a very fast-growing annual with seeds that are small and light enough to be blown by the wind over short distances and can sometimes survive for decades in the soil. Under favorable conditions, these three weeds can establish themselves quickly and spread profusely.
This summer weed rapidly removes moisture from soil, so remove it as soon as possible!
Cultivate this weed out of your garden using a sharp hoe.
If you wish, you can eat lambsquarters (assuming you’re not using chemicals). The young shoots and leaves can be eaten raw in any vegetable dish, or sauteed or steamed like spinach. See our natural health blogger’s post on Anytime Salad.
3. Pigweed (Amaranth)
Image: Pigweed. Credit: United Soybean Board.
Pigweed or Amaranth wins the title of most “problematic” weed. Amaranth has evolved traits that makes it a tough competitor, especially in broadleaf crops like soybeans and cotton.
An annual weed that reproduces by seeds, pigweed is characterized by its fleshly, red taproot. This weed appears in late spring or early summer and likes warm weather.
Try to pull out this weed before it flowers!
To prevent pigweed in the future, cover your garden plot with a winter mulch, then till the garden shallowly in early spring. When you till you may bring up some pigweed seed so it’s best to mulch again. Cover the soil with five layers of wet newspaper and cover that with 3-6 inches of mulch.
Pigweed is also edible—though usually only when young and tender, and when taken from a pesticide-free area. In June, the young leaves of Amaranthus blitum or amaranth are abundant and should be eaten because of their high nutritional content. Vitamin-wise, these greens are packed like carrots and beets and can be delicious in a tossed salad. You can also cook them as you would spinach. Native Americans used the black seeds of this plant as a ground meal for baking.
4. Buckhorn Plantain
Buckhorn plantain. Photo by Oregon State University.
A hardy perennial that reproduces by seeds. This narrow-leafed weed invades meadows, pastures, and lawns. This weed appears in any season.
Hand weed this plant and destroy it to remove it from your garden.
Plantain’s also edible, especially when the leaves are young and tender. Enjoy raw, steamed, boiled, or sauteed.
Crabgrass. Photo by R. Dyer/Bugwood.org
Crabgrass is a low-growing, summer annual that spreads by seed and from rootings of nodes that lie on the soil. Unmowed, it can grow to 2 feet tall.
This weed appears from mid-spring through summer when the ground is warm. It grows well under dry, hot conditions.
As an annual, crabgrass dies at the end of each growing season, usually at the first frost in the fall, and it must produce new seeds every year.
Fortunately, crabgrass is easy to manage. Controlling crabgrass before it sets seed is important, because the seeds can remain viable for at least 3 years in soil.
In the lawn, mowing regularly is often all you need to prevent them from flowering and producing seed. Most experts recommend that you mow your lawn to a height of 2 to 4 inches and that you mow frequently enough to keep it within that range.
Also, if you keep a lawn, be sure to select grass adapted to your location so it’s a healthy, thick lawn. Because seedling crabgrass isn’t very competitive, a vigorously growing turf will crowd out new seedlings. Perennial ryegrass is the best competition for crabgrass. It also provides some insect control, as it emits a natural poison that gives some small, damaging bugs the “flu.” Fertilizing is key and must be done in the spring and in the fall. Crabgrass thrives in compacted lawns, so aeration can help. A mixture of 1 pint of hydrogen peroxide, diluted to 3 percent, per 100 square feet of lawn can help eradicate the pesky plant.
In gardens, you easily can control crabgrass by mulching, hoeing, and hand pulling when the plants are young and before they set seed. You also can control this weed with solarization. Several chemical herbicides are available but often aren’t necessary. Mulching with wood products (e.g. wood chips or nuggets), composted yard waste, or synthetic landscape fabrics covered with mulch will reduce crabgrass in shrub beds and bedding plants and around trees by blocking sunlight needed for its germination, establishment, and growth.
Organic mulches that have been on the soil for a while decomposing can provide an adequate growth medium for weeds to germinate and grow in. If crabgrass is germinating in the mulch, move it about with a rake to reduce seedling establishment. Hand pull escaped crabgrass plants before they set seed
If you’re using herbicides, apply pre-emergent herbicides before crabgrass germinates or post-emergent herbicides after it germinates. Avoid using chemical herbicides in vegetable gardens because of the variety of crops grown and planted there.
Photo: Quackgrass in strawberry garden.
A creeping, persistent perennial grass that reproduces by seeds. Its long, jointed, straw-colored rhizomes form a heavy mat in soil, from which new shoots may also appear.
Try to dig out this weed as soon as you see it in your garden.
Mouse-ear chickweed. Photo by Oregon State University.
There are two species of chickweed, common (Stellaria media) and sticky (Cerastium glomeratum), which grow easily in gardens, low-maintenance lawns, and agricultural areas. Mouseear chickweed (Cerastium fontanum ssp. vulgare) is a perennial also found in lawns.
When growing without competition from other plants, common chickweed can produce approximately 800 seeds and it takes 7 to 8 years to eradicate. Chickseed thrives in moist, cool areas so it often gets started before spring crops can become competitive and can limit vegetable harvest.
Fortunately, annual chickweed is easier to control as long as you control before it flowers. This can be difficult due to the short period between germination and flower production so you need to keep an eye out for this weed. Both types have shallow roots, so they can often be removed by hoeing or hand-pulling if done early. It is most effective if the soil is dry and plants are small.
New plants can grow from broken pieces of mouse-ear rootstock, however, so make sure you remove the entire plant when using either method. Herbicides should only avoided in the vegetable garden.
Using an organic mulch such as wood chips, at least two inches deep, will reduce the amount of weed seeds germinating by limiting light and serving as a physical barrier. Synthetic mulches such as landscape fabrics may also be used. In landscaped areas, they should be covered with an additional layer of mulch (rock or bark). Vegetable gardens also can utilize black plastic, both as mulch into which seeds or transplants are placed and also between rows.
A healthy lawn can compete against mouse-ear chickweed if the grass is not mowed too short or too frequently. Watering the lawn deeply and infrequently will encourage the grass to grow deeper roots, which also can help it compete against chickweed. Water once every seven to ten days, and apply enough water so that it soaks six to eight inches into the ground.
Chickweed is also edible. When young, the leaves, stems, and flowers can all be eaten either raw or cooked, where it adds a delicate spinach-like taste to any dish.
Ah, we love much about dandelions with their bright yellow heads in the springtime. They provide a lovely source of food for bees early in the year, and the jagged leaves of this perennial (Taraxacum officinale) are even edible, especially when young and tender. The flowers, too, can be eaten raw or fried, or used to make dandelion wine! Here are a few dandelion recipes: Dandelion Recipes
In time, however, dandelions will also take over any habitat from your garden to your ornamentals to your grasses. They have the most weedy characteristics of all the weeds. Not only do dandelions have wind-borne seed but also reproduce vegetatively thanks to large tap roots. So unless you cut the root deep into the soil, you can rest assured the plant will reemerge.
Removing dandelions by hand-pulling or hoeing is often futile, unless done repeatedly over a long period of time, because of the deep tap root system of established plants. But if you have a small area, pull young dandelions by grasping them firmly by their base and wiggling gently, as you must dislodge their deep taproot from the soil. Alternatively, use a hand trowel to dig them out. Try to remove the whole dandelion root at once, as any piece left in the ground will probably grow back.
If you keep a lawn, a vigorous (and competitive) lawn will slow down dandelion infestation. Dense turfgrass and ornamentals shade the soil surface, reducing the establishment of new dandelion seedlings. Many broadleaf weeds may be controlled with mowing but this is NOT true of dandelion. Because it grows from a basal rosette that is lower than a mower blade can reach, mowing will have no effect on control.
For a garden bed, mulches of wood chips or bark are effective if they are maintained at a depth of least 3 inches deep (and replaced over time). Mulching with landscape fabrics can be particularly effective for controlling seedlings, reducing the amount of light that is able to reach the soil. Use a polypropylene or polyester fabric or black polyethylene (plastic tarp) to block all plant growth.
Solitary new dandelion plants along fence rows, roadsides, flower beds, and in turfgrass should be grubbed out (removed by digging out the entire plant, taproot and all) before they produce seed. Dandelion knives and similar specialized tools are available for removing individual weeds and their roots while minimizing soil disturbance. Monitor the area for several months to make sure that removal of the taproot was complete.
If you’re using herbicides, consider pre-emergence herbicides such as those containing dithiopyr or isoxaben because they are applied to the soil BEFORE the seeds germinate.
Purslane is an annual succulent that reproduces by tiny black seeds and stem fragments. This weed appears in late spring or early summer and likes warm weather, fertile soil and moist garden beds.
Purslane produces over 2,000,000 seeds PER PLANT! Wow. Purslane also can reproduce vegetatively through its succulent leaves, making it especially tough to eradicate. Many a gardener hoed purslane one day only to see it growing at full strength the next.
The primary method of management for common purslane is prevention. In home landscapes and gardens, this weed is generally managed by hand-weeding. Pull out this weed as soon as you see it and destroy the plant; this weed can live in your soil for years!
Young purslane is edible, too! It’s a nutritional powerhouse and a great addition to a salad or stir-fry. See purslane’s health benefits and find a recipe here.
Mulching is also helpful, especially in garden beds. To be effective, organic mulches should be at least 3 inches thick. Synthetic mulches (plastic or fabric mulch) which screen out light and provide a physical barrier to seedling development, also work well. Fabric mulches, which are porous and allow flow of water and air to roots, are preferred over plastics. Combinations of synthetic mulches with organic or rock mulches on top are commonly used in ornamental plantings.
10. Shepherd’s Purse
Shepherd’s Purse. Photo by Oregon State University.
A flowering annual that reproduces by seeds. It likes cool weather and its yellowish-brown seeds are long-lived in the ground.
Try to pull out this weed before it seeds.
11. Nutsedge (Yellow, Purple)
Image: Yelllow Nutsedge
Nutsedges are perennial weeds that superficially resemble grasses, but they are thicker and stiffer and V-shaped. Their leaves are arranged in sets of three from their base instead of sets of two as you would find in grass leaves. They are among the most problematic weeds for vegetable crops and can greatly reduce harvest yields. Yellow nutsedge has light brown flowers and seeds, while purple nutsedge flowers have a reddish tinge and the seeds are dark brown or black.
If you have nutsedge, it’s often an indicated that your soil drainage is poor or waterlogged. However, once nutsedge is established, it’s very difficult to control.
The best approach is to prevent establishment of the weed in the first place.
Remove small plants before they develop tubers. Tubers are key to nutsedge survival. If you can limit production of tubers, you’ll eventually control the nutsedge itself. Most herbicides aren’t effective against tubers.
Also, eliminate the wet conditions that favor nutsedge growth. Use mulches in landscape beds. Landscape fabrics are the best mulch because the sharp leaves of nutsedge can pierce other mulches.
12. Canada Thistle
Canada thistle (Cirsium arvense) is an aggressive, creeping perennial weed from Eurasia. It infests crops, pastures, and non-crop areas like ditch banks and roadside. Canada thistle reduces forage consumption in pastures and rangeland because cattle typically will not graze near infestations.
Introduced perennial from Eurasia. Reproduces by seeds and whitish, creeping rootstocks which send up new shoots every 8 to 12 inches. Plants 2 to 4 feet tall, It is a colony-forming weed, reproducing asexually from rhizomatous roots (any part of the root system may give rise to new plants) or sexually from wind-blown seed. The plant emerges from its roots in mid- to late spring and forms rosettes.
Then, it will send up shoots every 8 to 12 inches. The plants will grow 2 to 4 feet tall. You may spots its purple flowers are produced in July and August.
Canada Thistle is difficult to control because its extensive and deep root system allows it to recover from control attempts. Horizontal roots may extend 15 feet or more and vertical roots may grow 6 to 15 feet deep! Seeds may retain viability 4+ years in the soil.
The first plants need to be destroyed by pulling or hoeing before they become securely rooted. Look for Canada Thistle above ground in early spring.
If Canada Thistle becomes rooted, the best control is to stress the plant and force it to use stored root nutrients. It’s at its weakest during the flowering stage in summertime; this is a good time to begin cultivation and destroy the roots and rootstock. One season of cultivation followed by a season of growing competitive crops such as winter rye, will go a long way toward eradication.
An approved herbicide, applied for two years in an established in a thistle-infested area, is an effective control. Usually, a combination of techniques is needed. Consult with your cooperative extension office for an approved herbicide and suggested program.
13. Creeping Charlie
Creeping Charlie (Glechoma hederacea), also called “ground ivy,” is a herbaceous perennial plant that enjoys moist and shady areas. Native to Europe, it has become an invasive lawn weed in North America. The plant has bright green leaves with scalloped edges on creeping stems that root at the nodes. It tends to form a dense mat over the ground.
The reason Creeping Charlie is so challenging is the way it spreads—by both seeds and by creeping stems (called stolons) that grow along the ground. If you try to dig it out and leave behind a fragment of rhizome (root), even a tiny piece can grow up as a new plant!
To control, improve soil drainage or water less frequently to dry the soil. If Creeping Charlie is invading a thin lawn, try to improve turf health and density to get weeds under control. This can be accomplished by mowing regularly (to a height of two to three and one-half inches), fertilizing and watering appropriately, and overseeding in the fall. Also, make sure to grow the most suitable type of turfgrass for the location (e.g., plant shade tolerant turfgrass varieties under trees).
Alternatively, consider removing grass and growing shade-loving plants such as vinca, English ivy, pachysandra, or hosta that compete well with weeds (though they can also become weeds themselves, so plant at your own risk!). In areas where Creeping Charlie has become established, try removing plants by hand. This is the control method of choice in vegetable or flower gardens. Try to pull the weed without breaking it and over time it may give up.
However, this may not be a viable option in heavily infested areas, as the extensive spreading stems of creeping Charlie can be difficult to completely remove. If you have mats of weed, smother with newspaper or tarp. Once plants are pulled, make sure to dispose of the plants in such a way that they cannot re-root.
Borax, once used for organic control, is not recommended for creeping Charlie (or other broadleaf weed) control. It does not provide long-term control of creeping Charlie, and can injure turf and other plants, causing stunting and yellowing.
Often, herbicide applications are a necessary last resort. Consult your local garden center or cooperative extension for the appropriate herbicides in your local area.