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Chicory
Cichorium intybus

IDENTIFICATION — The line between wildflower and weed can be narrow. With chicory, or blue sailor weed as it’s sometimes called, what one person considers a lovely blue flower, a neighbor might consider a weed. This is one of those perennials that can go either way.

In summer, branched flower stems spring up from the center of a low rosette of leaves that looks very much like a dandelion. These tough stems can reach more than 7 ft. tall, but the average is usually less than 3 ft. The leaves along the tough stems are small and not very noticeable. Underground there’s a fleshy taproot that if broken, will “bleed” a milky white sap. But the daisylike flowers (usually blue, but sometimes pink or white) are what you’ll notice first.

Each morning the flowers open facing the rising sun. They last just one day, so by late afternoon they fade and wither. But rest assured there will be more tomorrow morning.

You can eat tender young chicory leaves in salads or as a cooked green. Roots are cooked and eaten or dried and ground to make a coffee substitute.

FAVORITE CONDITIONS — This European native has naturalized across much of North America. You’ll spot it growing along roadsides or the edge of your garden. It does not like areas that are frequently cultivated or mowed to less than 2 in. tall.

CONTROL — Just like a dandelion, chicory spreads mainly by seeds, so you’ll want to keep it from setting seeds. However, pieces of root will also grow quite easily. Repeatedly mowing the plant short, or cutting it off at the soil line will eventually kill it. The taproot is hard to pull from the ground, even after soaking the area with water first. Broadleaf or non-selective herbicides are also effective at getting rid of chicory.

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Fuller’s teasel
Pastinaca sativa

IDENTIFICATION — Originally introduced from Europe for use as a dried flower, Fuller’s teasel has naturalized in much of North America. The first year, this biennial forms a rosette of oblong leaves that may grow to nearly 12 in. long. During the second year, several flower stalks with spines shoot up nearly 6 ft. The spiny egg-shaped lavender flowers bloom from June to October. After flowering and producing seed, the plant dies.

FAVORITE CONDITIONS — Fuller’s teasel prefers open, sunny sites like roadsides and disturbed areas, although it may grow in your lawn or garden. It’s a particular pest for restored prairies and wildlife areas because each plant is capable of producing more than 2,000 seeds and most of them will germinate. Under favorable growing conditions, it can actually outcompete native prairie plants.

CONTROL — As with all biennial weeds, it’s easier to manage Fuller’s teasel in the rosette stage. Use a dandelion-puller to pull out the long tap root or slice it off, below the soil, with a sharp spade. And as with dandelions, be sure to get as much of the root as possible so it won’t resprout. You can cut off the flower head to prevent it from going to seed. Herbicides that contain triclopyr or glyphosate can also be used, but are most effective when applied while the plants are in the rosette stage before they flower.

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Wild parsnip
Pastinaca sativa

IDENTIFICATION — This invasive biennial is related to the edible parsnips you may grow in your vegetable garden. Like its cultivated cousin, wild parsnip has a long, white-yellow taproot that is edible.

The first year, a rosette of leaves emerges and grows to about 1 ft. tall. Egg-shaped leaflets are in pairs along the stem and are deeply toothed or lobed. During the second year it sends up a thick, grooved flower stalk. Bright yellow flowers in flat clusters, like dill, appear from May to October. Flowering plants may grow as tall as 5 ft.

FAVORITE CONDITIONS — Wild parsnip spreads by seed and grows just about anywhere in North America in fields, ditches, prairies, bike paths, cultivated gardens and even your lawn. Although it prefers full sun and moist to wet soils, it will grow in shade and dry soils, too.

CONTROL — Hand digging wild parsnip is the most effective control method. But the deep taproot can make it difficult. If possible, identify and dig up plants when they’re in the rosette stage and the tap root is short and easier to dig. Cut or mow flower stalks on mature plants to prevent seeds from forming. Then dig up as much of the plant as you can. Herbicides that contain glyphosate, such as RoundUp^®, can be an effective control. Follow label directions. Wear long sleeves, pants and gloves when handling wild parsnip because it exudes a chemical that causes photodermatitis blisters when your skin is exposed to sunlight. These can become very painful and may require medical attention.

Click on the photo to see a larger image.

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Prostrate spurge
Euphorbia supina

IDENTIFICATION — The stems and undersides of the leaves of 2-in.-tall prostrate spurge have a red tint. If you break the somewhat hairy stems, they ooze a milky sap.

FAVORITE CONDITIONS — This mat-forming annual weed is often found from summer to fall in dry, gravelly to sandy soil in full sun. It thrives in full hot sun, even coming up in cracks of concrete, and is a prolific seeder.

CONTROL — Despite having a central tap root, prostrate spurge is easy to pull or hoe.

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Common mallow
Malva neglecta

IDENTIFICATION — Common mallow is a relative of hollyhocks that produces pink, pale blue or white summer flowers. It is sometimes called cheeseweed because the seed pods that follow the blooms are shaped like segmented wheels of cheese. These pods turn brown in summer and split open to release seeds.

FAVORITE CONDITIONS — In full sun to light shade and moist soil, common mallow can sprout in fall or early spring, producing flowers and seeds the following summer.

CONTROL — This weed has a short taproot, which makes it easy to pull or hoe.

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American elder
Sambucus canadensis

IDENTIFICATION — A quick way to identify this tree seedling is to crush a stem or a few leaves and you’ll get a disagreeable odor. Break or cut a mature stem and you’ll discover a spongy white pith in the center. And last but not least, the creamy white flowers in spring and the dark purple fruits that follow are in large, flat-topped clusters.

FAVORITE CONDITIONS — Full sun to part shade in moist, fertile soil is where you’re likely to find American elder. It also tolerates moderately dry conditions.

CONTROL — Pull or dig out saplings or spray with a nonselective herbicide like Roundup^®.

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Musk thistle
Curduus nutans

IDENTIFICATION — All the surfaces of the leaves and stems of musk thistle are covered with sharp prickles. The spiny multi-branched stems reach 2 to 6 ft. tall. From summer to fall, its showy red-purple flowers open, the flower heads drooping as they age.

FAVORITE CONDITIONS — The seeds of this biennial weed sprout in summer, in full sun or shade, in areas not regularly cultivated, such as fence rows, garden perimeters and lawns.

CONTROL — Sharp spines make hand-pulling this weed difficult. So hoe the young plants or spray a broadleaf herbicide before the seeds ripen.

PHOTO: © Jerry Pavia

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Chameleon plant
Houttuynia cordata

IDENTIFICATION — Often sold as an ornamental, the leaves of chameleon plant are green with margins of red, bronze or yellow and have a pungent odor when they’re crushed. The plant reaches 6 to 12 in. tall and spreads by underground rhizomes, rooting stems and seeds.

FAVORITE CONDITIONS — It prefers wet soil in sun or shade; in dry shade situations it spreads much slower.

CONTROL — Start digging and keep digging or spray with a nonselective herbicide. If you want to keep some, plant it in a buried container so the roots can’t run.

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Red clover
Trifolium pratense

IDENTIFICATION — Red clover is cultivated as a hay crop in agricultural areas, but is considered a weed elsewhere. It has fuzzy red-pink flowers and a V-shaped marking on each leaf. It can reach 20 in. tall.

FAVORITE CONDITIONS — You’ll most likely find red clover growing in sunny areas along garden edges and perennial borders, but rarely in tilled areas. It’s quite tolerant of wet soil conditions.

CONTROL — The stems of this weed root at nodes wherever they touch the soil. A broadleaf herbicide is the best control.

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Japanese knotweed
Polygonum cuspidatum

IDENTIFICATION — This extremely invasive weed has simple medium-green leaves and spike-shaped pale-green to white flowers in summer. By the end of summer the plant can reach to 8 ft. tall.

FAVORITE CONDITIONS — Japanese knotweed spreads by rhizomes in full sun and dry soil. Cultivated areas, such as garden beds, and waste areas are where you’ll find this pest.

CONTROL — Use a nonselective herbicide like Roundup^® as the plant is starting to go dormant in early fall.

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Buffalo bur
Solanum rostratum

IDENTIFICATION — Buffalo bur grows up to 2 ft. tall and is armed with long yellow spines on its deeply lobed light green leaves and along sturdy stems. In summer, small clusters of bright-yellow flowers form, followed by spiny seed pods.

FAVORITE CONDITIONS — Any dry, exposed soil in full sun is ideal for buffalo bur. Unfortunately, the weed is even drought-tolerant.

CONTROL — The simplest control for buffalo bur is to hoe out the young seedlings. Because of the sharp spines on the flowers, stems and seed pods, wear gloves to pull older plants.

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Eastern poison oak
Toxicodendron toxicarium

Western poison oak
Toxicodendron diversilobum

IDENTIFICATION — As with their close relative, poison ivy, “Leaves of three, let it be” is good advice. Eastern and Western poison oak both have three-leaflet leaves, with red-tinged new foliage and green-white fruit in late summer. Both species grow as small shrubs or vines up to 20 ft. long.

All parts of poison oak contain an oil called “urushiol.” About 90 percent of humans are allergic to this compound, and it causes severe itching and blistering on skin. The more you’re exposed to poison oak, the more likely you are to become sensitive to it, so don’t assume that you’re immune just because you’ve never reacted before.

FAVORITE CONDITIONS — Eastern poison oak is found mainly in the southeastern quarter of the United States, from Florida into Kansas. Western poison oak is found in California, Oregon and Washington and British Columbia. Both species are common in fence rows, waste land, stream banks and wild areas — and unfortunately, also in gardens.

CONTROL — It’s important to remove or kill the entire plant when you’re dealing with poison oak because it regrows from even small portions of the roots. You can pull seedlings or small plants by hand, but be very careful. Urushiol on gloves or clothing can get on your skin, so you’ll need to wash anything you’re wearing — even shoes. Don’t burn the pulled-up plants because inhaling the smoke can cause throat and lung irritation. It’s not a good idea to put them in the compost pile either, so put the plants in a heavy paper bag and dispose of them with your yard waste.

Using herbicide is often the easiest way to get rid of large, old plants. Systemic herbicides with glyphosate (like Roundup^®) will kill poison oak. But it’s most effective when you apply it in late summer, after fruit have formed but before the leaves turn red. You may need to apply it more than once. Because the herbicide will kill any plant it comes in contact with, be careful not to get it on any nearby ornamental plants.

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White clover
Trifolium repens

IDENTIFICATION — This low, 4- to 12-in.-tall spreading weed has white flowers and roots wherever stem nodes touch the soil, but it also spreads by seed. Some folks plant white clover because it adds nitrogen to the soil, which keeps the grass green during heat and drought.

FAVORITE CONDITIONS — White clover thrives in full sun in areas that are rarely tilled, such as lawns and perennial borders.

CONTROL — Broadleaf herbicides, especially those containing 2,4-D, are the most effective means of control for white clover. If you have white clover growing in your lawn, a fall application of nitrogen feeds the grass while it controls this weed.

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Sulfur cinquefoil
Potentilla recta

IDENTIFICATION — This 2-ft.-tall perennial weed blooms with sulfur-yellow flowers from late spring to late summer. The plant has stout, hairy stems and leaves with five to seven deep lobes. It spreads by seeds and also by root pieces that are left in the soil.

FAVORITE CONDITIONS — Sulfur cinquefoil needs a place in full sun and is usually found in dry, alkaline soil in rarely cultivated areas.

CONTROL — Hand pull or hoe, making sure to remove all parts of the root. Broadleaf herbicides containing 2,4-D are also effective.

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Black nightshade
Solanum nigrum

IDENTIFICATION — This rambling, 1- to 2-ft.-tall annual weed blooms all summer with clusters of star-shaped white flowers with yellow centers. Large quantities of berries turn dull black when ripe and are toxic to humans and animals but are eaten by birds. Each berry contains up to 60 seeds.

FAVORITE CONDITIONS — Black nightshade grows in sun or shade almost anywhere but prefers rich, moist soil.

CONTROL — Before it sets seed, pull and remove all parts of the plant. Even small stem pieces dropped on the ground can root and regrow. A pre-emergent herbicide, such as Dacthal, can be applied in the spring to prevent seed from germinating.

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Narrowleaf hawksbeard
Crepis tectorum

IDENTIFICATION — At 8 to 20 in. tall, narrowleaf hawksbeard looks like a dandelion on steroids. In fact, this edible annual’s leaves can be used just like a dandelion’s, as a green in salads. Plants grow upright, branching stems from a long, thin taproot. The toothed edged leaves get narrower and smoother near the top of the stems. A single, daisylike yellow flower forms at the end of each branch.

FAVORITE CONDITIONS — Hawksbeard was introduced from Europe and isn’t picky about where it lives. Sandy, loam or clay soils are all fine. And it grows in full sun to part shade. It’s found in tilled, moist soils, like vegetable gardens, throughout Canada and the northern tier states, the Midwest and on both coasts from Washington to Southern California and Maine to South Carolina. It seems to avoid the desert Southwest and Deep South.

CONTROL — These plants reproduce by seed. Although they can appear most any time during the growing season, the main flush emerges from mid-May to mid-June and from early August to mid-September. They flower in July and August and set seed through the fall. Preventing the seeds from setting and being dispersed is the best long-term control.

Although this isn’t a major turf weed, if you do find it in your lawn, mow back the plant before it flowers. Or use a postemergent, broadleaf herbicide that contains 2,4-D, like Trimec®, mid-April through early June and September and October, when the weed is actively growing. Avoid using 2,4-D in July and August. In high heat and dry conditions, it could damage or discolor a lawn. Remember, broadleaf herbicides can injure or kill vegetables, flowers and ornamentals, as well as weeds. So don’t let herbicide sprays or granules come into contact with them in the garden. Instead, hoe out sprouting hawksbeard seedlings. For more mature plants, dig down at least 3 in., loosen the soil around the taproot and try to pull the weed out whole.

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Field bindweed
Convolvulus arvensis

Don’t let this morning glory lookalike fool you — it will take over your garden if you let it.

IDENTIFICATION — Native to Europe and Asia, field bindweed is a perennial with arrowhead-shaped dark-green leaves along a vine 1 to 4 ft. long. White, pink or pink and white, 1-in. trumpet-shaped flowers bloom in spring in the South and by midsummer in Northern gardens. Twining up through other plants or along the ground, field bindweed creates large islands as more stems sprout along the fibrous, horizontal root system. In addition, roots can reach 10 to 20 ft. below the surface. As if the deep roots weren’t enough, bindweed reproduces by seed, too.

FAVORITE CONDITIONS — Field bindweed grows throughout most of the United States and Canada, except for the southernmost parts of the Southeast, southern Texas, New Mexico and southern Arizona. This weed isn’t picky about soil and grows in anything from loam to heavy clay. You’ll see it in gardens, ditches, along roadsides or any open area in full sun.

CONTROL — The key to beating this pest is to deprive the roots of nourishment as much as possible. It’s not easy, but persistence pays off. Apply a glyphosate herbicide, such as Roundup®, to mature plants before they set seed. Unfortunately, repeat applications are usually necessary. Be careful using this systemic herbicide around the garden plants you want to keep — it’ll kill them, too.

You can also try digging the roots out. Dig down at least 6 in. and 3 or 4 in. out from the main rhizome. Use a digging fork rather than a spade to avoid breaking up the roots. Dispose of the plants in the garbage. Then cover the area with landscape fabric or a 3- to 4-in.-thick layer of mulch to discourage resprouting. No matter what method you choose, keep the flowers clipped to prevent seeds from forming. One plant may produce up to 550 seeds, which can remain viable in the soil for 50 years.

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Purple loosestrife
Lythrum salicaria

IDENTIFICATION — Is it a weed? Is it an ornamental? It’s both. This square-stemmed, woody perennial grows in every state except Florida, and its sale as an ornamental is prohibited in many of those states.

Purple loosestrife was imported from Europe as an ornamental in the 1800s. Its magenta flower spikes, which bloom all summer, lead to it quickly spreading across the country. One mature plant can produce 2 to 3 million seeds per year. And in wet areas, it spreads underground by about a foot per year.

FAVORITE CONDITIONS — It prefers moist soil, especially areas of standing water and full sun. There it reproduces quickly and can grow up to 10 ft. tall. The stems and roots are so tough that boats and wildlife can’t get through a large stand of it. And it’ll quickly squeeze out less aggressive native plants.

CONTROL — Hand pull purple loosestrife before it sets seed in home gardens. Eradicate large stands in late summer with glyphosate herbicides. Be sure to follow the instructions for applying any chemical, particularly near water. Parasitic insects that feed on roots and leaves have been introduced into wild areas of purple loosestrife as biological controls.

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Broadleaf plantain
Plantago major

IDENTIFICATION — The presence of broadleaf plantain is a concern for multiple reasons. Not only is this weed unwanted, but it indicates that the soil is compacted. Spikes of tiny flowers stand 6 in. above a rosette of leaves in summer. Crushed leaves sooth the itch of poison ivy.

FAVORITE CONDITIONS — Broadleaf plantain thrives in part to full shade in damp, compacted soil. It can be found in lawns and at the edge of the garden.

CONTROL — Young plants can be hoed or pulled out, but older plants are tougher to remove. Dig them out with a shovel or use a broadleaf herbicide, especially in lawns.

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Chickweed
Stellaria media

IDENTIFICATION — This broadleaved annual creeps low to the ground, growing roots at nodes that touch the soil. Chickweed has slender, branching stems with a row of white hairs on one side of each branch, small pointed leaves and tiny white flowers that appear from midwinter to early spring.

FAVORITE CONDITIONS — Found throughout North America, this cool-season weed grows in fall to spring. It usually dies in the heat of summer. But in cool, shady gardens it may thrive year-round.

CONTROL — Hand pull the entire weed. Pieces left on the ground may reroot. Spray with a broadleaf-herbicide that contains triclopyr or a non-selective herbicide that contains glyphosate. As always, follow label directions when applying herbicides.