Yellow Nutsedge (Cyperus esculentus)

Family:

Sedge Family (Cyperaceae)

Other Names:

chufa, coco, cocosedge, earth almond, edible galinglae, edible nutgrass, ground almond, northern nutgrass, rush nut, tiger nut, watergrass, yellow nutgrass.

Origin and Distribution:

Yellow nutsedge is native to North America and Eurasia, but is found throughout the world. Although it is of subtropical origin, this species has spread north into temperate regions. Prior to 1950, is was found mostly in native habitats, but today it is considered one of the world's worst weeds. Yellow nutsedge is especially troublesome in the northcentral and northeastern U.S. It is common throughout Ohio, where it occurs naturally in marshes and along riverbanks and lakeshores, and as a weed in cultivated fields, turf and gardens. It is especially common in poorly drained areas, but can tolerate upland sites as well. This species tolerates a wide range of soil types from sand to clay.

Plant Description:

Yellow nutsedge is an erect, grass-like perennial, characterized by its shiny yellowish-green leaves, triangular stem, golden-brown flower head and shallow rhizomes (horizontal underground stems) that produce many nut-like tubers. Young seedlings are often confused with grasses. This species reproduces primarily by tubers and less often by seeds. Rhizomes help to enlarge patches.

  • Root System:

    Yellow nutsedge forms a complex, shallow underground system composed of fine fibrous roots, thin scaly rhizomes (horizontal underground stems), hard spherical tubers and basal bulbs (swelled rhizome tips which produce stems and leaves). Roots are produced from rhizomes, tubers and basal bulbs. Two types of rhizomes are formed. Short rhizomes are produced from germinating tubers, and end in basal bulbs. Long wiry rhizomes are produced from basal bulbs, and can grow 2 to 8 inches long (sometimes up to 24 inches). Long rhizomes can end in either tubers or basal bulbs. Tubers (1/5 to 4/5 inch long) are white at first, turning brown and eventually black at maturity.

  • Stems:

    Stems (1/3 to 3 feet tall) are erect, hairless, unbranched and triangular in cross-section.

  • Leaves:

    The leaves are light yellowish-green (4 to 12 inches long or longer, 1/8 to 1/2 inch wide) with a prominent mid-vein, a waxy surface and a gradually tapering, pointed tip. Leaves are arranged in 3's and form a sheath around the stem. Most leaves are produced toward the base of the plant. A set of 3 specialized leaves (bracts) (1 to 8 inches long, 1/8 to 1/2 inch wide) occurs just below the flower head.

  • Flowers:

    Inconspicuous flowers are arranged into numerous, flat, narrow, straw-colored clusters within a branched, umbrella-shaped flower head at the top of the stem

  • Fruits and Seeds:

    Fruits are oval, 3-angled, single-seeded, and yellowish brown.

Similar Species:

Small yellow nutsedge plants or young shoots are often confused with young annual grasses, but can be distinguished by triangular stems that are apparent if you roll the stem between your finger and thumb or look at the stem in cross section near the base of the plant. Grass stems are flat or round. A related species, purple nutsedge (Cyperus rotundus), can be distinguished from yellow nutsedge by its generally darker leaves and red-brown to purple flower clusters. Unlike yellow nutsedge, which produces tubers only at rhizome tips, purple nutsedge produces a chain of tubers along the length of the rhizome.

Biology:

Flowering occurs from July to September. Seed germination begins in May. Tuber germination typically begins as soil temperatures reach about 54 Farenheit degree (12 Celsius) (in May), and shoots continue to emerge through mid-July. Tuber formation begins in late July and continues through the rest of the growing season.

Yellow nutsedge reproduces and spreads primarily by tubers, which are the only structures (besides seeds) that can survive the winter. All foliage, rhizomes, roots and basal bulbs die with the first hard frost. Viable seeds are produced, but tend not to be an important means of reproduction since seedling survival is low. When a tuber germinates in the spring, several short rhizomes are formed, ending in a basal bulb near the soil surface. Basal bulbs generate stems and leaves above the ground and fibrous roots and long rhizomes in the soil. Long rhizomes produce basal bulbs or tubers at their tips (usually basal bulbs are produced early in the season and tubers late in the season as the day length shortens). Basal bulbs sprout immediately to form new shoots, roots and rhizomes, and rhizomes go on to produce more basal bulbs (which germinate immediately) and tubers. This process continues throughout the season. Tubers remain dormant over the winter, and many germinate the following spring. Most tubers remain viable for no more than 3 years (rarely 10 years). Basal bulbs are usually found 3/4 to 2 inches below the surface, and over 75% of tubers are formed within the top 6 inches of the soil. Shaded conditions severely limit tuber production. Tubers are easily spread by farm equipment and on crop transplants. Since rhizomes lack buds, new plants cannot be produced from rhizome fragments.

Yellow nutsedge is especially troublesome in agriculture because it is adapted to many crops and tillage systems. Some herbicides commonly used in corn and soybeans are not very effective on yellow nutsedge and serve only to eliminate other competing weeds, thus allowing yellow nutsedge to survive and spread. This species is also troublesome because it competes with crops for water, nutrients and light, and suppresses crop growth by producing toxic compounds in the soil (allelopathy). With high populations of yellow nutsedge, allelopathy can suppress the growth of young corn, soybean, and other crop plants. A density of about 10 yellow nutsedge plants per square foot reduces corn yields about 8%. Each plant can produce hundreds to thousands of tubers per season, and in densely infested fields, this adds up to 10 to 32 million tubers per acre. Rhizomes can penetrate potato tubers. Control of yellow nutsedge may be aided by improved drainage, crop rotation, several years of fallow, or shallow cultivation throughout the growing season (while tubers are sprouting) to prevent the formation of new tubers.

Toxicity:

None known.

Facts and Folklore:

  • The scientific name of yellow nutsedge means 'abundant edible sedge'. Tubers have a mild, starchy taste, slightly reminiscent of almonds. Ancient wall paintings from Egypt indicate that this plant was cultivated as early as 400 BC. It is still grown in the Spanish-Mediterranean region, where tubers are used to make a nonalcoholic beverage

  • Pigs are reported to be very fond of the starchy tuber.

  • A Wisconsin field was reported to have up to 35,200,000 yellow nutsedge tubers per acre.

  • Four weedy varieties and one cultivated variety of yellow nutsedge are currently recognized.

  • An African variety called chufa (Cyperus esculentus var. sativas) is grown in the southeastern U.S. for its edible tubers.

  • Papyrus (Cyperus papyrus), a related species, grows 10 feet tall and was used in Ancient Egypt for making paper.