Witch grass, Panicum capillare

Life Cycle

Annual

Propagation

Reproducing only by seed.

Stems

Stems 5 - 120 cm high, erect, or spreading.

Leaves

Leaf blades and leaf sheaths densely hairy, the hair 2 - 3 mm long and becoming harsh and prickly as the plant matures; leaf sheath split (B), its margins (a) either separate or overlapping; ligule (b) a dense fringe of hair 1 - 2 mm (1/25 - 1/12 in.) long; no auricles.

Flowers and Fruit

Inflorescence (C) a large, loose, open, fluffy panicle with numerous, very fine branches and tiny spikelets (d) at the ends of those branches; the much-branched panicle often wider than long and, on small- to medium-sized plants, often making up ½ to 2/3 the total height of the plant; mature spikelets 0.7 - 0.8 mm wide by 2.0 - 2.3 mm long florets (“seeds”) 0.6 - 0.7 mm wide and 1.3 - 1.4 mm long shiny gray-brown with 5 parallel beige veins. At maturity, the stem breaks easily below the inflorescence and the whole panicle is rolled and tumbled by the wind, dropping seed with every bounce. Flowers from July to September.

Roots and Underground Structures

Fibrous root system.

Habitat

Witch grass is very common in fields, waste areas, roadsides, backyards, gardens and occasionally in lawns throughout southern Ontario and sporadically in northern and northwestern Ontario.

Competitiveness

Corn yield loss (%)*: 1 % at 1 plant/m2 5 % at 5 plant/m2 Soybean yield loss (%)*: 1 % at 1 plant/m2 4 % at 5 plant/m2 *assumes that the weed has emerged with the crop and has been left uncontrolled all season.

Distinguishing Features

It is distinguished from Fall panicum by its densely hairy leaves and leaf sheaths, its very fine, bushy panicle and its smaller seeds; and from Proso millet by its much smaller seeds that are only gray-brown in colour. Seedlings of Witch grass can be distinguished from those of Proso millet only by the size, shape and colour of the mother seed clinging to the primary root.

Toxicity

Witch grass is not known to be toxic.

Human Health Issues

Witch grass is not a known allergen.

Forage Quality

No information exists at this time.

Species Benefits

No information available at this time.

Power Ranking Corn

Power Ranking

↑ 22

 

Power Ranking Soybeans

Power Ranking

↑ 35

 

Biological Control

Currently none available for this weed. For the latest research on biological weed control: http://res2.agr.ca/Lethbridge/weedbio/index_e.htm#toc

Biopesticide Control

Currently none available for this weed.

Herbicide Resistance

Triazine resistant (WSSA group 5) populations exist in Grenville, Grey, Haldimond/Norfolk, Prescott and Wellington counties (ON). For more information on weed resistance: http://www.plant.uoguelph.ca/resistant-weeds/


Figure #1.

Witch grass: A. Base of plant B. Leaf-base C. Panicle


Figure #2.

Ligule: hairy.


Figure #3.

Leaf blade: hairy on the upper and lower surfaces.


Figure #4.

Leaf sheath: extremely hairy, leaf sheath margins are also hairy.


Figure #5.

Seed head.


Figure #6.

Whole plant.