Yellow nutsedge [Cyperus
esculentus L.][CYPES][CDFA list: B] Map
of Distribution Photographs
Purple nutsedge [Cyperus
rotundus L.][CYPRO][CDFA list: B] Map
of Distribution Photographs
DESCRIPTION:Perennials with grass-like
leaves, triangular stems, and rhizomes with small
tubers attached. Both species are among the most noxious
of agricultural weeds in temperate to tropical regions worldwide.
They often form dense colonies, can greatly reduce crop yields,
and are difficult to control. In California, nutsedges are especially
troublesome in annual and perennial crops that receive summer
irrigation. Elsewhere yellow nutsedge is grown for its
edible, earthy almond-flavored tubers. Purple nutsedge tubers
taste bitter and are used medicinally in China and India. Yellow
nutsedge is a widespread, highly variable native of North
America and Eurasia. Purple nutsedge is introduced from
Eurasia and is often called the "worlds worst weed."
to those of mature plants but smaller. Stem base slightly triangular.
Midvein region often pale. First 2-3 leaves emerge simultaneously
and are folded lengthwise.
erect, simple, glabrous, triangular in cross-section. Leaves
3-ranked, mostly basal, glossy, glabrous, often creased
lengthwise. Leaves lack ligules, auricles, and collar regions.
Margins finely serrate. Sheaths closed, membranous, pale
back to top of
and UNDERGROUND STRUCTURES:Plants develop extensive systems of rhizomes,
tubers, and roots. Rhizomes produce tubers and basal bulbs
that bear aerial shoots. Tubers store starch and have several
buds that produce rhizomes, which develop more basal bulbs and
new plants. Roots often grow to greater soil depths than tubers
or rhizomes. Rhizomes slender, fleshy when young, covered with
loose, umbel-like, with leaf-like bracts at the base. Spikelets
consist of several to ~ 40 florets. Achenes +/- elliptic, triangular
in cross-section, 1-1.5 mm long, seldom mature.
CHARACTERISTICS:Foliage dies back with cool temperatures in fall,
but tubers survive and resprout the following spring.
cultivated fields, especially those irrigated in summer, irrigation
ditches, orchards, vineyards, gardens, turf, landscaped areas.
Typically grows where moisture is plentiful. Tolerates many soil
conditions, including periods of drought and flooding. Yellow
nutsedge often grows on sandy, well-drained soils.
from tubers and by seed. Tubers and seeds disperse
with agricultural and nursery activities, soil movement, and in
water, especially flooding. Seeds also disperse with wind. Seeds
and tubers germinate in spring. Tubers develop to soil depths
of ~ 32 cm, but most are in the top 20 cm. One plant can produce
hundreds to thousands of tubers in one season. Seed production
can be high, but viability is variable. In California, seed viability
is typically low. One plant can develop into a dense colony 3
m (10 ft) or more in diameter. Patch boundaries can increase by
more than 1 m per year.
FAVORING/DISCOURAGING SURVIVAL:Limit tuber production and drain tuber energy reserves
by repeatedly removing small plants before the 6-leaf stage (every
2-3 weeks in summer). Mature tubers can resprout up to ~12 times.
Shading or solarization can reduce infestations by weaking shoots
and decreasing new tuber formation, but mature tubers may not
be eliminated. Cultivation can worsen an infestation if not repeated
often enough to exhaust tubers and prevent new tuber formation.
SIMILAR SPECIES:Yellow and purple nutsedge
are the only sedges in California that have tubers. Unlike the nutsedges, grass
species have 2-ranked leaves with ligules and round or flattened stems, never
A comprehensive nutsedge management guide has been developed
by the University of California (UC ANR Publication 7432) authored by Cheryl
Wilen, Milton McGiffen Jr., and Clyde Elmore. The management guide can be accessed
online at the following address: http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7432.html