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



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[
SYNONYMS] [GENERAL DESCRIPTION] [SEEDLINGS] [MATURE PLANT] [ROOTS and UNDERGROUND STRUCTURES] [SPIKELETS/FRUITS] [POSTSENESCENCE CHARACTERISTICS] [HABITAT] [DISTRIBUTION] [PROPAGATION/PHENOLOGY] [MANAGEMENT FAVORING/DISCOURAGING SURVIVAL] [SIMILAR SPECIES] [CONTROL METHODS]

SYNONYMS:

GENERAL 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 "world’s worst weed."

SEEDLINGS:Leaves similar 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.

MATURE PLANT:Stems 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 green.

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ROOTS 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 scales.

SPIKELETS/FRUITS:Inflorescences 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.

POSTSENESCENCE CHARACTERISTICS:Foliage dies back with cool temperatures in fall, but tubers survive and resprout the following spring.

HABITAT:Disturbed areas, 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.

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DISTRIBUTION:Nearly worldwide.

PROPAGATION/PHENOLOGY:Reproduce vegetatively 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.

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MANAGEMENT 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 triangular.

CONTROL METHODS:

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

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