Winter Annual Weeds
Click for larger image Common chickweed (Stellaria media)--also called, Alsine media, starwort, starweed, bindweed, winterweed, satin flower, tongue-grass--can be a pest of the lawn or garden

Annual winter weeds germinate in the fall and winter and grow actively in spring. Gardeners are often surprised how quickly these weeds can seemingly pop up overnight in their yards and gardens, being unaware that they may have been growing slowly all winter long. After they flower in spring they die and disappear for the summer only to return in fall or winter when new seeds germinate.

Some of the more common annual winter weeds in the Midwest are henbit, deadnettle, common chickweed, annual bluegrass, wild mustards, prickly lettuce, Persian speedwell, horseweed, cheatgrass and rabbitfoot clover. Some people do not consider these plants as weeds, as some can also be used for food or have been used for medicinal purposes.

Deadnettle and Henbit

Deadnettle (Lamium purpureum) and henbit (Lamium amplexicaule) are often confused. These winter weeds are both in the mint family and have square stems with opposite leaves. Both plants have pink/purple flowers and can reach 16 inches high but more commonly reach only about 6 inches high in the Midwest. Henbit has circular or rounded leaves with rounded teeth on the leaf margin. Deadnettle has triangular shaped leaves and less deeply lobed than henbit and at times the upper leaves are purple or red. Both plants are decumbent in youth but more upright with age. Flowers appear in whorls in the leaf axis of upper leaves from March to May and are tube-like with 2 lips.

Common Chickweed

Common chickweed (Stellaria media) is a winter annual with a shallow fibrous root which grows in moist, cool shaded areas. The bright green leaves are about ½ inch long, smooth, pointed at the tip, and elliptic in shape. They have opposite branching, slender, creeping stems which root at the nodes. The white flowers of chickweed are ½ inch in diameter and star-shaped with five deeply notched petals. Flowering occurs from early spring to fall. Chickweed reproduces by seed and rooting at the nodes on prostrate stems. The fruit contains many seeds within a dry capsule which splits when mature, shaking out the seeds onto the soil. Seeds will germinate at any time of the year but particularly in spring and autumn. Seeds are dispersed in mud on footwear and tires as well as by animals. Chickweed is found in turfgrass as well as nursery, cultivated horticultural, and agricultural crops. It is a host of several damaging virus diseases of crop plants which can be carried in the chickweed seeds.

Annual Bluegrass

Annual bluegrass (Poa annua) is one of the most common weeds in the United States. It is a native of Europe. Golf courses consider it a particular problem. It is identified by its boat-shaped leaf tips which curve up like the bow of a boat. Annual bluegrass is upright growing (growing 3-12" high) and can be noticed by its pale green spring appearance. It can produce 100 seeds in 8 weeks. It germinates when the temperature falls below 70 degrees and throughout the winter. It usually dies in the summer.

Prickly Lettuce

Prickly lettuce (Lactuca serriola) is in the aster family. It can grow up to 5’ tall. Sometimes this winter weed can be a biennial. It has creamy yellow aster-like flowers. Butterfly larvae feed on this plant. Alternate leaves branch off the main stem. There is a prominent midvein on each leaf which contains a row of spines on the bottom surface. Several edible lettuces, such as crisphead, butterhead, cos, Romaine, loose leaf or bunching, and stem lettuce or celtuce were all derived from this species.

Persian speedwell

Persian speedwell (Veronica persica) is a winter annual with slender, weak stems that grow along the ground but turn up at the tips. In shaded areas it tends to grow more upright. The stems are covered with finely pointed, flattened hairs. The hairy leaf blades are oval to roundish with rounded teeth around the edges. The lower leaves are arranged oppositely and occur on petioles, but the upper leaves occur on the more erect flowering stems, are arranged alternately, and do not have petioles. The flowers occur singly on long, slender flower stalks which arise from the leaf axils. The small flowers are usually light blue in color with darker blue lines and a pale blue to white center. Prior to flowering, the speedwells are often misidentified as ground ivy, henbit, or purple deadnettle. However, ground ivy does not have hairy leaves and both henbit and purple deadnettle have leaves that are arranged oppositely along the flowering stem. Speedwell is primarily a weed of lawns, turfgrass, landscapes, nurseries, and winter small grains.

Horseweed

Horseweed or mare's tail (Conya canadensis) can grow to 6 1/2 ’ tall. A mature plant has alternate leaves that have no petiole. Young leaves are egg-shaped with toothed margins but mature leaves are 3-4 inches long, hairy, and oblanceolate in shape (broader and rounded at the apex, and tapering at the base.) Plant has a taproot. Small inconspicuous flower heads are at the top of the central stem. Flowers are about 1/4 inch in diameter, with white or slightly pink ray flowers. This is a composite flower and there are many tiny disk flowers in the flower head (like daisies and coneflowers). In the early stages, this plant resembles shepherd’s purse or Virginia pepperweed. The fruit (or seed) is a 1/16 inch long achene that does not split open when it is ripe. It tapers from the apex with many small bristles that aid in wind dispersal. This plant is susceptible to aster yellows.

Cheatgrass

Cheatgrass (Bromus tectorum) is a winter annual that has a fine feathery appearance, with slender light-green stems drooping at the tips where the seeds form. Seed spikelets and their bristles can be 2 inches long. Mature grass grows to 30 inches and turns first purple, and then brown, as it dries. Cheatgrass occurs throughout most of the United States and is on state noxious weed lists in 43 states. It grows on rangelands, pastures, prairies, fields, eroded sites and roadsides. Cheatgrass can alter ecosystems by maintaining dominance for years on sites where native vegetation has been eliminated or severely reduced due to grazing, cultivation, or fire. Moreover, it increases the frequency and timing of wildfires. At maturity the sharp-pointed bristly sections can injure wildlife species by working into the nose, ears, mouth, or eyes. Spikelets can also cling to clothing.

Rabbitfoot Clover

Rabbitfoot clover (Trifolium arvense) is in the pea family. This winter weed has a multi-branched growth habit and is 4-16 inches tall. It came from Eurasia and is naturalized now. Both stems and leaves are densely hairy. Leaves consist of 3 narrow leaflets with minute teeth-like projections at the tip. Flowers are small and pink to purple in color. They are clustered in grayish soft and silky cylinder-shaped heads. It flowers in the spring, and reproduces by seed. Rabbitfoot clover is found in the Southeast United States, west to Louisiana and north to Missouri. Rabbitfoot clover contributes nitrogen to the soil, as do other clovers, but it grows in unimproved sandy soils in semi-arid grasslands.

Bedstraw

Bedstraw (Galium aparine) is a winter annual with square stems and short, downward pointing hooks on the stem corners. The stems are weakly branched, prostrate on the ground or climbing on other plants producing a tangled mass. The rough hairy leaves grow in whorls of six to eight. The tiny white flowers have four-lobed pointed petals on long flower stalks. Bedstraw is found in moist shady areas, thickets, valleys, roadsides, waste ground, under trees, and clearings. The hooked spines of the stems, leaves and seeds cling to just about everything and are difficult to remove. The burr-like seeds are produced in pairs and are covered with hooked hairs. This clinging characteristic minimized matting when bedstraw was used as a mattress filling.

Shepherd's Purse and other mustards

Shepherd’s purse (Capsella bursa-pastoris) is a winter annual with erect stems that grow 3 to 18 inches tall from a basal rosette quite similar to that of a dandelion. The rosette grows to be 4 to 8 inches in diameter. Shepherd’s purse has alternate leaves with the lower leaves more deeply lobed than the upper leaves. The flowers are small and white, appearing in clusters at the top of the stalk from early spring to early winter. Each flower has four petals and develops into a heart-shaped or triangular seedpod which, when the pod dries, splits in half releasing the mature seeds. The seedpods are supposed to resemble the purses of ancient shepherds. It does best in sunny, rich, disturbed soil, but it will also grow in partly shaded, extremely poor soils.. It can be found in flowerbeds, lawns, sidewalk cracks and along the edges of sidewalks and paths.

Integrated Pest Mangement Strategies

1. Encourage grass. Keep lawn areas thick and mulch flowerbeds to help prevent weed seeds from germinating.

2. Removal. Dig or pull the weeds in the winter or spring before they flower and set seed for the next year.

3. Good sanitation. Use good cultural and sanitation practices to prevent the spread of weeds. Small weed seeds can be spread by machines, clothing, pets, and by contaminated seed.

4. Use chemical herbicides. For established weeds the best time to apply herbicides is early spring when the weeds are actively growing but before they go to seed. Herbicides containing Dicamba and/or MCPA or MCPP are more effective than 2,4-D alone. After you have identified the weed you have, check product labels or resource materials to see which herbicides are most effective for that weed or combination of weeds. Use herbicides with caution around desirable plants that may be damaged. Read label directions and cautions carefully.

5. Use pre-emergent herbicide. To prevent germination of the seeds of these winter annuals, apply a pre-emergent herbicide, such as, Gallery in late summer or early fall before the weed seeds have germinated.

(The following Weed ID pages with good images of the weeds are linked to with permission of UMass Extension.)

Weed ID links Weed ID links Weed ID links
Arenaria serpyllifolia (sandwort, thymeleaf ) Lactuca serriola (lettuce, prickly) Ranunculus abortivus (buttercup, smallflower)
Barbarea vulgaris (rocket, yellow) Lamium amplexicaule (henbit) Brassica kaber (mustard, wild)
Capsella bursa-pastoris (shepherd's-purse) Lamium purpureum (deadnettle, red) Sisymbrium officinale (mustard, hedge)
Cardamine hirsuta (bittercress) Lepidium campestre (pepperweed, field) Stellaria media (chickweed, common)
Conyza canadensis (horseweed) Lepidium virginicum (pepperweed, Virginia) Thlaspi arvense (pennycress, field)
Erodium cicutarium (filaree, redstem) Matricaria matricariodes (pineappleweed) Veronica arvensis (speedwell, corn)
Hibiscus trionum (mallow, venice) Potentilla norvegica (cinquefoil, rough) Veronica peregrina (speedwell, purslane)

Organic Strategies

Strategies 1, 2, and 3 are strictly organic approaches.

More images:

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Catchweed bedstraw (Galium aparine) with purple-flowering henbit (Lamium amplexicaule) in front
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Field pennycress (Thlaspi arvense), an introduced weed species, also called Frenchweed, fanweed, stinkweed
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Field pennycress (Thlaspi arvense), an introduced weed, also called Frenchweed, fanweed, stinkweed; note, the distinctive shape of the seed pod
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Catchweed bedstraw (Galium aparine); also called, cleavers, goose-grass, scratch-grass, grip-grass
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Corn speedwell (Veronica arvensis); note spreading habit
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4 petaled blue flower of corn speedwell (Veronica arvensis)
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Heart-shaped, hairy seedpod of corn speedwell (Veronica arvensis)
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Red deadnettle (Lamium purpureum) can be a pest of the lawn or garden
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Henbit (Lamium amplexicaule)--also called, dead nettle, blind nettle, bee nettle--can be a pest of the lawn or garden
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Henbit (Lamium amplexicaule)--also called, dead nettle, blind nettle, bee nettle--can be a pest of the lawn or garden
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Red deadnettle (Lamium purpureum)
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Annual bluegrass in fescue (Festuca) lawn
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Annual bluegrass in fescue (Festuca) lawn
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Henbit (Lamium amplexicaule)--also called, dead nettle, blind nettle, bee nettle--can be a pest of the lawn or garden
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Close-up of henbit (Lamium amplexicaule)--also called, dead nettle, blind nettle, bee nettle--which can be a pest of the lawn or garden
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In the spring passersby seeing a field of henbit in bloom may think it's beautiful, but the owner of the field probably considers this winter annual a difficult-to-control weed
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Spreading chervil or Chaerophyllum procumbens is sometimes called wild chervil
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Bedstraw, a common weed of the lawn and garden, can be easily pulled when small
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Chickweed with flower, a common weed of the lawn and garden
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Henbit (Lamium amplexicaule), a common weed of lawns, gardens, and fields
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Henbit (Lamium amplexicaule), a common weed of lawns, gardens, and fields
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Spreading chervil or Chaerophyllum procumbens is sometimes called wild chervil
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Chickweed (Stellaria media) and henbit (Lamium amplexicaule) growing in the spaces left by sparsely seeding a fescue lawn (Festuca)


Pests and Problems

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