Agriculture - Witchgrass

Witchgrass

A member of the grass family, witchgrass (Panicum capillare) is an erect annual weed that has a shallow fibrous root system and reproduces by seed.

1. Fuzzy seedling of witchgrass.

Seedling Description

The stems of witchgrass seedlings are erect, slightly oval, and green, often tinged with purple. Both stems and leaf sheaths are densely covered with stiff hairs up to 1/8 inch (3 mm) long. Hairs stick straight out from the stem and give the weed a fuzzy appearance. Young leaves are rolled in the bud. When fully emerged, they taper evenly to a pointed tip. Both surfaces of the leaves are covered with soft short hairs, and the leaf margins have similar hairs on the lower (basal) half of the leaf blade. Leaf sheaths are split and the margins may be overlapping or separate. The ligule is a row of short hairs. Auricles are absent.

Biology

A member of the grass family, witchgrass is an erect annual weed that has a shallow fibrous root system and reproduces by seed. It grows 10 to 30 inches (25 to 76 cm) tall, usually in tufts or bunches, because its stems branch at the base. The stems are extremely hairy, especially at the nodes. Leaf blades are 6 to 12 inches (15 to 30 cm) long and ¼ to ½ inch (6 to 13 mm) wide. Soft erect hairs cover both surfaces, especially near the base of the blade; the tip end of the leaf is less hairy. The leaf sheaths are covered with dense, soft hairs up to 1/8 inch (3 mm) long that stand straight out from the surface and become quite harsh and bristly as the grass matures.

2. Plants become hairier as they mature.
3. Short hairy ligule.

The purple or green seed heads (panicles) are quite large, often one half to two thirds the size of the entire plant. Leaves may hide the base of the seed head until midsummer when the seeds begin to mature. The panicle then opens to form a wide-spreading, branched inflorescence with hundreds of tiny florets on threadlike stalks. Each floret produces a single seed about 1/16 inch (1 mm) long.

When the grains ripen, the stem of the seed head becomes brittle and breaks off easily. The whole panicle of springy fine branches drifts and bounces along in the wind like a tumbleweed, scattering seeds over great distances. Witchgrass spreads quickly once introduced to an area.

4. Emerging seed heads resemble a witch's broom.
5. Witchgrass produces a profusion of tiny seeds.
6. Tire wispy panicle is pyramid shaped.

Similar Species

Fall panicum (Panicum dichotomiflorum) is closely related to witchgrass, but has a smooth shiny stem. Witchgrass has a fuzzy stem, even in the seedling stage. The closely related wild proso millet (Panicum miliaceum) has a hairy stem, but its seedhead is distinctly drooping, while that of witchgrass is stiffer and more erect. Several brome grasses have similar hairy sheaths and stems. These are hairy chess or cheat (Bromus commutatus), downy brome (B. tectorum), and soft chess (B. mollis). However, the ligules of all three of these grasses are membranous, while the ligule of witchgrass is a row of short hairs.

Natural History

Witchgrass is native to the eastern United States and is a common weed in cotton, alfalfa, com, and other cultivated row crops. It prefers dry soil but adapts well to irrigated crops and gardens. Witchgrass grows in meadows, cultivated fields, and waste ground, and along stream banks and roadsides. It is more common east of the Rocky Mountains than in the western United States, but it does grow throughout the country at elevations between 100 and 8,000 feet. Witchgrass grows throughout the Northeast but is not quite as common as the closely related fall panicum (Panicum dichotomiflorum). It is often introduced to field crops when its seed contaminates small crop seed, especially alfalfa.

The young panicle of witchgrass looks like a pointed shaving brush or a witch's broom. Witchgrass is known by other common names, including ticklegrass, hairgrass, panic grass, and tumble grass.

Control

Witchgrass can be controlled by many of the methods used to control other annual grass weeds. Several cultural methods can help prevent problems. Clean cultivating may be done late in the season to destroy young plants and prevent seed formation. Also effective are mowing waste places before seeds form and pulling or hoeing scattered plants while they are small.

Witchgrass is one of the few weeds unaffected by the herbicide atrazine. When this chemical is used for weed control, other weeds are eliminated, and the absence of competition allows witchgrass to flourish. When witchgrass is among the weeds infesting agronomic crops, a combination of several herbicides should be used.

For specific recommendations, consult your county Extension agent or the most recent Weed Control Manual and Herbicide Guide, available through Meister Publishing Company, 37841 Euclid Avenue, Willoughby, Ohio 44094. Follow label instructions for all herbicides and observe restrictions on grazing and harvesting procedures.

Prepared by W. Thomas Lanini, Extension weed specialist, and Betsy Ann Wertz, agricultural writer.

Reference: http://extension.psu.edu/pests/weeds/weed-id/witchgrass