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
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.
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.
(Cyperus esculentus): Sedge family; perennial; grasslike;
light green blades, flat, slender; leaf tip long and drawn
out; nutlets globe shaped, smooth, and almond flavored.
(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.
(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.
(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.
(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.
(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
(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.
(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.
(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.
(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.
(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.
(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.
(Avena fatua): Grass family; winter annual; first leaves
with small marginal hairs and counterclockwise twist when viewed
from above; ligule large, papery, and pointed.
(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
(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.
(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
(left to right: barley, wheat, oat collars)
(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.