UC IPM Online UC ANR home page UC IPM home page

UC IPM Home

SKIP navigation

 

Potato

Problem Weeds—Previous Crop and Preplant

On this page
  • Quackgrass
  • Nutsedge
  • Hairy nightshade
  • Black nightshade
  • Mustards
  • Pigweed
  • Common lambsquarters
  • Wild oat
  • Burning nettle
  • Wheat (volunteer grains)

Special management practices may be required to control these weeds before planting potatoes. Use the photos below to identify weeds in the field. Names link to information on identification and biology.s

Click on photos to enlarge
Seedling Mature
Quackgrass
Quackgrass
Elytrigia repens (=Elymus repens): Grass family; perennial; occurs in cooler Northern California and coastal areas; first leaf blade narrow with short, membranous ligule that is minutely fringed; auricles may be undeveloped or difficult to see; leaf blades light green or covered with a white bloom; sheaths smooth or hairy; difficult to distinguish from other grass seedlings; perennial rhizomes develop by the 6- to 8-leaf stage.
Quackgrass
Quackgrass
Elytrigia repens (=Elymus repens): Grass family; perennial; occurs in cooler northern California and coastal areas; erect, stems single or forming clumps; leaf surface hairy above and hairy or smooth below; ligule membranous, minutely fringed; auricles slender, clasp the stem, whitish to violet tinged; flower heads closely resemble those of ryegrass, spikelets flattened with flat side facing stem; forms extensive system of straw-colored rhizomes.
Young yellow 
				nutsedge plant.
Yellow nutsedge
(Cyperus esculentus): Sedge family; perennial; grasslike; light green blades, flat, slender; leaf tip long and drawn out; nutlets globe shaped, smooth, and almond flavored.
Nutsedge
Nutsedge
(Cyperus spp.): Sedge family; perennial; leaves V-shaped in cross section, arranged in sets of three at base; stems triangular in cross section; yellow nutsedge can be distinguished from purple nutsedge via the tubers; yellow nutsedge tubers are produced singly on rhizomes while purple nutsedge tubers are produced in chains with several tubers on a single rhizome.
Hairy 
				nightshade seedling.
Hairy nightshade
(Solanum sarrachoides): Nightshade family; summer annual; seed leaves narrow, small, and lance shaped with very short soft hairs along edges; first true leaves with wavy edges and prominent veins.
Hairy nightshade
Hairy nightshade
(Solanum sarrachoides): Nightshade family; summer annual; bushy; stems and leaves covered with conspicuous hairs, sticky to the touch; flowers usually white, petals form star-shaped corollas; fruit green when mature, sepals cover about half the fruit; each fruit contains 10 to 35 small, tan to yellow, oval, flattened seeds.
Black 
				nightshade seedling.
Black nightshade
(Solanum nigrum): Nightshade family; summer annual or short-lived perennial; seed leaves oval and pointed; first true leaves spade shaped with smooth edges; lower surfaces often purple; petioles stems and leaves with some hairs.
Black nightshade
Black nightshade
(Solanum nigrum): Nightshade family; summer annual or short-lived perennial; plants erect to bushy; stems and leaves smooth or with inconspicuous hairs, not sticky to the touch; flowers usually white, petals form star-shaped corollas; fruit black when mature, calyx lobes do not cover base of fruit; each fruit contains 15 to 60 small, yellowish to white, oval, flattened seeds.
Mustard 
				seedling.
Mustards
(Brassica spp.): Mustard family; winter annual; all mustard seedlings with broad seed leaves and deep notch at tip; first true leaves bright green on the upper surface and paler below.
Mustards
Mustards
(Brassica spp.): Mustard family; winter annuals; plants erect, branched; basal leaves lobed and stalked, upper leaves reduced and lacking stalks; yellow flowers with four petals in dense clusters at the tips of branches; fruit elongated, slender, beaked pods containing two rows of spherical to oval seeds.
Redroot 
				pigweed seedlings.
Redroot pigweed
(Amaranthus retroflexus): Pigweed family; summer annual; seed leaves long and narrow with red undersides; first true leaves with notched tips and much broader than seed leaves.
Redroot pigweed
Redroot pigweed
(Amaranthus retroflexus): Pigweed family; summer annual; plants erect with dense terminal masses of inconspicuous flowers; leaves alternate, on stalks, lower leaves oval or diamond shaped, upper leaves lance shaped; seed capsules contain single, lens-shaped, glossy, dark brown or black seed.
Seedling 
				of common lambsquarters, Chenopodium album.
Common lambsquarters
(Chenopodium album): Goosefoot family; summer annual; seed leaves are narrow, with nearly parallel sides; seed leaves and early true leaves dull blue green above and often purple below; young leaves have mealy appearance from coating of  fine translucent granules.
Common lambsquarters
Common lambsquarters
(Chenopodium album): Goosefoot family; summer annual; plants erect; leaves pale green with a white, powdery appearance; tiny flowers in dense, spike-like clusters at tips of main stem and branches; fruit smooth to irregularly textured, each containing one glossy, dark seed.
Wild oats seedling.
Wild oat
(Avena fatua): Grass family; winter annual; first leaves with small marginal hairs and counterclockwise twist when viewed from above; ligule large, papery, and pointed.
WIld oat
Wild oat
(Avena fatua): Grass family; winter annual; erect plants, several stems growing from the base of each plant; leaves often twisted counterclockwise, with sparse hairs on margin at base; ligule membranelike with rounded, jagged tip; auricles lacking; inflorescence openly branched with large spikelets; distinguished from cultivated oat by twisted awns bent at right angles when flowers mature and by horseshoe-shaped scar ("muleshoe") at base of seed.
Burning nettle 
				seedling.
Burning nettle
(Urtica urens): Nettle family; winter or summer annual; rounded seed leaves with smooth margin and small notch at tip; first true leaves with small notch at tip, opposite, stalked, and distinctly toothed.
Burning nettle
Burning nettle
(Urtica urens): Nettle family; winter or summer annual; plants erect, stinging hairs on stems, leaf stalks, and lower leaf surfaces; stems square in cross section, branching at base; leaves opposite; flower clusters mostly headlike, with male and female flowers in same cluster; single-seeded fruit oval, flattened, smooth, tan to yellow-brown.
Collar regions of 
				(left to right) barley, wheat, and oat.
(left to right: barley, wheat, oat collars)
Wheat
(Triticum aestivum): Grass family; winter annual; distinguished from most other grasses by ligules that clasp stem with slight overlap; barley plant ligules longer, with more overlap.
 

Top of page


Statewide IPM Program, Agriculture and Natural Resources, University of California
All contents copyright © 2014 The Regents of the University of California. All rights reserved.

For noncommercial purposes only, any Web site may link directly to this page. FOR ALL OTHER USES or more information, read Legal Notices. Unfortunately, we cannot provide individual solutions to specific pest problems. See our Home page, or in the U.S., contact your local Cooperative Extension office for assistance.

Agriculture and Natural Resources, University of California

Accessibility   /PMG/C607/m607epprobweeds.html revised: April 25, 2014. Contact webmaster.