Green foxtail, Setaria viridis

Life Cycle



Reproducing only by seed.


Stems erect or spreading, 10 - 100 cm tall or occasionally taller, usually round in cross-section but occasionally much flattened.


Leaves and leaf sheaths of very young plants often densely hairy but with upward-pointing hair; upper leaf blades and leaf sheaths mostly without hair; margins (a) and both surfaces (b) of leaf blades rough with very fine forward-pointing barbs; leaf sheath split with overlapping margins (c), both margins being fringed with a band of short hair (d); ligule (e) a fringe of hair 1.5 - 2 mm long; no auricles.

Flowers and Fruit

Inflorescence a very dense spike 1 - 15 cm long and 0.6 - 2.0 cm wide, usually straight and erect or rarely somewhat curved, the larger ones sometimes with short branches up to 1 cm long, and covered with short green to slightly purplish bristles which give the inflorescence a bottle-brush appearance; the bristles have microscopic forward-pointing barbs that allow the seed head to be dragged downwards but not pushed upwards over the skin or a rough surface. Spikelets about 2 mm long by 1 mm wide; each contains a single fertile floret (“seed” or “grain”), that is rounded on one surface but flattened on the other, finely cross-ridged (seen only with magnification), and dull yellowish-green with brownish spots. Flowers from July to August.

Roots and Underground Structures

Fibrous root system.


Green foxtail is very common and widespread throughout all agricultural regions of Ontario. It grows well in all soil textures and occurs in cultivated lands, waste places, roadsides, gardens and occasionally lawns.


Corn yield loss (%)*: 2 % at 1 plant/m2 7 % at 5 plant/m2 Soybean yield loss (%)*: 2 % at 1 plant/m2 8 % 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 Yellow foxtail by its green or purple bristles, the absence of long, kinky hair on the upper surface of the leaf blade near the stem, the presence of a fringe of hair (d) on both margins (c) of the leaf sheath, and its somewhat smaller grains or seeds. It is distinguished from Bristly foxtail by its denser, more continuous spike whose bristles do not cling when sliding the fingers upwards on it. It is distinguished from Giant foxtail by its usually shorter stature, its shorter, thinner and usually erect inflorescence (rarely curved or nodding) and the absence of a covering of short hair on leaf surfaces in the middle and upper parts of the plant.


Green foxtail is not known to be toxic.

Human Health Issues

Green foxtail is not a known allergen.

Forage Quality

No information exists at this time.

Species Benefits

No information available at this time.

Often Mistaken For

Fall panicum (PANDI), Giant foxtail (SETFA)

Power Ranking Corn

Power Ranking

↑ 3


Power Ranking Soybeans

Power Ranking

↑ 6


Biological Control

Currently none available for this weed. For the latest research on biological weed control:

Biopesticide Control

Currently none available for this weed in corn and soybean.

Herbicide Resistance

Sulphonylurea and imidazolinone resistant (WSSA group 2) populations exist in Huron, Lambton, Perth, Wellington and Victoria counties (ON). For more information on weed resistance:

Figure #1.

Green foxtail: A. Plant with stem folded twice. B. Leaf-base. C. Spike.

Figure #2.

Ligule: Hairy.

Figure #3.

Leaf blade: Smooth upper and lower surface.

Figure #4.

Leaf sheath: Hairy margins.

Figure #5.

Seed head.