Common Weeds of Summer in Northwestern Nevada

Transcription

1 Common Weeds of Summer in Northwestern Nevada Common Name ID Control Common lambsquarter Chenopodium album L. Chenopodiaceae (Goosefoot Family) Seedling leaves are grayish green Annual Grows upright to 5 feet tall Stems branch; sometimes have purplish red stripes Leaves are light gray green and triangular or goosefoot shaped and whitish underneath ( album ); usually covered in a powdery white coating Flowers are small, green and have no petals Leaves can be eaten raw or cooked Pull, hoe or dig early in season. Seedlings do not tolerate disturbance. Mow regularly. Does not tolerate routine mowing when in lawns, and will often disappear after 1 2 months of mowing. Remove plants before they produce seed May need to use preemergence herbicides to control seed bank Pesticide resistance to triazine and ALS inhibitors is a problem; resistance to glyphosate has been reported; try 2,4 D/dicamba or aminopyralid

2 Prickly lettuce Lactuca serriola L. Asteraceae (Sunflower Family) Annual to biennial Grows 1 to 6 feet tall Stems are hollow and branch into the flowering structure; can be smooth or prickly Leaves are alternate, lobed or entire, twisted at the base and have prickles on margin and on the lower side of the pale midrib; leaves clasp the stem Leaves and stems ooze a milky sap when cut Flower heads are yellow and look like dandelions Has a taproot Pull, hoe, or dig rosettes; mowing is not effective as plants grow flat when mowed Can be grazed by sheep or goats Apply herbicides to young, small plants Resistant to sulfonyl urea herbicides (ex. Telar, Escort); try 2,4 D/dicamba mixture or clopyralid, aminopyralid

3 Sweetclover (white and yellow) Melilotus alba (white) Melilotus officinalis (yellow) Fabaceae (Pea Family) Sweetclover is sometimes cultivated for livestock forage and as a cover crop; used by honey bees and comsumed by wildlife. Annual to biennial legume Can grow to 6 feet tall Alternate leaves; each leaf has 3 leaflets; margins are serrated or notched all the way around (vs. alfalfa, notched only towards the tip) Foliage is smooth; may have tiny hairs White or yellow pea like fragrant flowers Taproot Fixes nitrogen in the soil Can cause bloat in cattle; high in coumarin Need to control seed production Pull, dig, mow, hoe plants prior to seed set Avoid disturbing the soil by disking or blading, as this creates ideal growing conditions for sweetclover Plant competing vegetation Use herbicides on young plants; try 2,4 D/dicamba

4 Russian thistle Salsola tragus L. Chenopodiaceae (Goosefoot Family) Summer annual Commonly called tumbleweed Forms a bushy plant that breaks off and tumbles when dry, spreading seeds Stems usually have red or purple stripes Leaves are alternate; young leaves are long and look like pine needles; later leaves are short and tipped with sharp spines Flowers are tiny, green or pinkish/red and have no petals and sit above 2 spiny bracts in the leaf axils Taproot Need to control seed production Pull, dig, mow, hoe plants prior to seed set Avoid disturbing the soil by disking or blading, as this creates ideal growing conditions for Russian thistle Use herbicides on very young plants; mature plants are difficult to kill with herbicides; try 2,4 D/dicamba or glyphosate

5 Kochia Kochia scoparia L. Chenopodiaceae (Goosefoot Family) Summer annual Grows 1 to 6 feet tall Forms a rosette Stems branch from base, slender, usually softhairy but sometimes smooth, often striped with red Leaves alternate, lance shaped, entire and ½ to 2 inches Leaf blades have 3 or 5 prominent veins Leaf margins fringed with hairs; upper surface usually smooth and lower surface usually covered with soft hairs Flowers green, petal less, inconspicuous in dense, bracted spikes Mature plant is pyramid shaped Spreads by seed; must manage the seed bank Pull, hoe, dig rosettes Use preemergence herbicides Apply postemergence herbicides to young, small plants; mature plants are difficult to kill with herbicides; try 2,4 D/dicamba or glyphosate

6 Curlycup gumweed Grindelia squarrosa Asteraceae (Sunflower Family) Biennial to short lived perennial Grows 1 to 3 feet tall First year s growth is a rosette Has a deep taproot with shallow lateral roots Stems are branched and somewhat woody Alternate leaves have serrated margins and clasp the stem Flowers are bright yellow with bracts that curve downward Bracts secrete the sticky substance for which the plant is named Leaves are also sticky Grows along roadsides Dig rosettes in first year, removing as much of the taproot as possible Do not allow to flower Woody stems make it difficult to weed whack Use herbicides for large infestations; try 2,4 D/dicamba

7 Musk thistle Carduus nutans Asteraceae (Sunflower Family) Biennial Rosette leaves are broad & long; have frosted edges and pale midribs Stems are winged Leaves dark green with pale midrib; deep lobes and spiny margins Large taproot Grows to 6+ feet tall Single large (1½ to 3 inches across) flower at the end of a stem nods when mature; color is deep rose, violet, or purple Flower bracts are tipped with purple Dig rosettes in first year, removing 2 of the root below the crown Do not allow to flower Large plants can be clipped and then dug Use 2, D/dicamba, chlorsulfuron, clopyralid or aminopyralid with surfactant per label directions

8 Perennial pepperweed Lepidium latifolium Brassicaceae (Mustard Family) Perennial Grows a rosette Grows to 6+ feet tall (taller in moist sites) Lance shaped leaves attach with petioles; feel waxy Lower leaves are larger, upper leaves smaller Side stems emerge from junction of leaf to main stem giving a branched, bushy appearance Leaf margins smooth to toothed Small white flowers in dense clusters in racemes; flowers have 4 petals Reproduces by seed and creeping roots Creeping roots make this perennial weed difficult to control mechanically Can try repeated digging for a period of years; get as much root as possible Clipping blooms seems to stimulate the roots to send out shoots Herbicides are available; try 2,4 D, chlorsulfuron, metsulfuron, imazapyr or imazapic

9 Puncturevine Tribulus terrestris L. Zygophyllaceae (Caltrop Family) Summer annual Grows in a flat mat up to 5 feet wide Stems radiate from a central point Leaves are hairy and opposite and have 4 to 8 pairs of leaflets Flowers are yellow and have 5 petals Seeds have 5 parts that break apart into sharpspined goatheads Taproot Pull or hoe young plants Must control production of seeds, which is continual Mowing does not work (plants are too flat) Mulch with 4 inches of organic mulch or landscape fabric to exclude light There are effective biocontrol insects Herbicides can be used; try 2,4 D on young plants

10 Prostrate knotweed Polygonum arenastrum Polygonaceae (Buckwheat Family or Knotweed Family) Annual to short lived perennial Grows in a flat, round shape Stems are wiry and are enlarged at each joint; highly branched Oval leaves are bluish green Stipules are silvery and membranous White to green or pinkish flowers are tiny and appear in the axils Does NOT ooze milky sap when stem is broken (vs. spurge) Taproot; difficult to pull in compacted soils Pull, hoe or dig early in season Use 3 4 inches of organic mulch or use landscape fabric to exclude light Herbicides can also be used; try 2,4 D/dicamba, chlorsulfuron or clopyralid Avoid compacting the soil

11 Spotted and prostrate spurge Chamaesyce maculate, prostrata L. Euphorbiaceae (Spurge Family) Classified as the same species Summer annuals Grow in flat, dense mats Leaves are opposite and dark green; purple spots in spotted version Hairy stems and leaves ooze an irritating sap when broken Tiny pinkish flowers in leaf axils consist only of pistils and stamens Common in lawns Prevent seed production Wearing gloves, pull, dig or hoe plants Try solarization Use 3 4 of organic mulch or landscape fabric to exclude light Herbicides can be used; try 2,4 D/dicamba on very young plants

12 Field bindweed Convolvulus arvensis L. Convolvulaceae (Morningglory Family) Perennial Vining plant that climbs or produces mats Stems are 1 to 4 feet long Leaves are alternate, shaped like arrowheads; stalks are grooved on the upper surface Flowers are white to pinkish and shaped like bells (typical morningglory flowers) Spreads by rhizomes and extensive root system Massive root system makes this plant difficult to control Pull, cultivate or hoe every 2 to 3 weeks to control young plants Use black plastic mulch; must exclude all light; monitor for several years Apply herbicides to young, actively growing plants; 2,4 D/dicamba only suppresses plants; try metsulfuron, imazapic; glyphosate on actively growing plants Prevent seed production Plant forms: July 2010