Giant Foxtail
Grassy weed
Giant foxtail (Setaria faberi) is a warm-season annual grass introduced from Asia that has become one of the most common weeds in Midwestern crop fields, gardens, and disturbed ground. Gardeners and growers notice it because of its tall, arching, bristly seedheads and its ability to build up a large seed bank in a single season.
How to identify it
Giant foxtail grows in an upright clump from 2 to 7 feet tall, taller than the other common foxtails. Its leaf blades are broad and flat with a distinctive band of short, soft hairs across the upper surface, and the leaf collar carries a ligule that is a fringe of tiny hairs rather than a membrane. The seedhead is a dense, cylindrical, spike-like cluster covered in fine bristles that nods or droops over at the tip, giving it a fox-tail look. It has a shallow, fibrous root system and no rhizomes or stolons.
Where it grows
It thrives in row crops such as corn and soybeans, along with vegetable gardens, field edges, roadsides, and recently disturbed or tilled soil. Seeds germinate through the warm months from late spring into summer, and the plant completes its life cycle in a single growing season. Giant foxtail spreads only by seed, and a single vigorous plant can produce thousands of seeds that remain viable in the soil for several years.
Why it is a problem
Because it grows tall and fast, giant foxtail competes strongly with crops and garden plants for light, water, and soil nutrients, and heavy stands can noticeably reduce yields. Its prolific seed production quickly builds a persistent seed bank that makes it harder to control in later seasons. The stiff, barbed bristles on the seedheads can also work into the mouths, gums, and skin of grazing livestock and pets, causing irritation.
How to manage it
Since giant foxtail reproduces only by seed, the most important step is preventing plants from maturing and setting seed. Pull or hoe seedlings while they are small, and use shallow cultivation to cut off young plants before the seedheads form; in gardens, a layer of mulch blocks light and greatly reduces germination. Mow field edges and open areas before the bristly heads develop, and keep turf and crop stands dense and vigorous so a competitive canopy shades out new seedlings. Clean soil and plant debris off tillers, mowers, and boots to avoid moving seed to clean ground, and stay consistent over several years to draw down the seed bank.
Commonly confused with
It is easily confused with green foxtail and yellow foxtail, which are shorter with more upright, non-nodding seedheads; green foxtail has mostly smooth leaves, and yellow foxtail shows long hairs near the leaf base and yellowish bristles, while giant foxtail is larger with a drooping head and hairy upper leaf surfaces.
General guidance for US lawns and gardens, focused on prevention and non-chemical control. For a confirmed identification and options specific to your area, contact your local Cooperative Extension office. Page updated Aug 4, 2026.