What is giant foxtail?

Giant foxtail is a summer annual grass from eastern Asia that arrived in the 1920s and now grows in every corner of the country. It’s one of the most common grass weeds in Pennsylvania crop fields, and it moves right into gardens, new lawn seedings and any patch of bare soil. Giant foxtail identification comes down to one feature most people notice first: a fuzzy, bottle-brush seed head that bends over at the tip.

Because it’s an annual, it dies at the first hard frost and comes back the next year only from seed. That’s good news, because it means stopping seed production is the whole game.

Giant foxtail identification: what to look for

Giant foxtail is the largest of the three foxtails you’ll run into in central PA. Left alone in a garden it often reaches 2 to 4 feet.

• Seed head: A dense, bristly, cylinder-shaped head, several inches long, that arches or droops over as it matures. Yellow and green foxtail heads stand straight up.
• Leaves: Wide, flat blades, up to an inch across, with many short hairs on the upper surface. Run your fingers along the top of the leaf and it feels slightly fuzzy.
• Collar: At the point where the leaf blade meets the stem, the ligule is a short fringe of hairs. There are no ear-like auricles.
• Growth habit: Upright clumps that send up several stems from the base as the plant gets older.

Seedlings can be hard to tell apart from other grasses, so it’s often easiest to confirm the ID once the first heads appear in July.

Where it grows in Pennsylvania

Giant foxtail loves disturbed, sunny ground. You’ll find it in vegetable gardens, corn and soybean fields, freshly graded yards, new lawns seeded in spring, mulch beds where the mulch has worn thin, and along roadsides and construction sites.

Seeds start sprouting in late spring once the soil warms and keep coming through midsummer, mostly from the top inch of soil. In a healthy, established lawn it’s uncommon, because mowing and thick turf keep it from getting started.

Where it does get into a lawn, it usually means the soil was bare in late spring. New construction lots, trenches for drain lines and yards that were reseeded in May are the usual spots, and the clumps stick out as coarse, wide-bladed tufts among finer grass.

Giant foxtail look-alikes

Yellow foxtail has an upright seed head that turns golden and a few long, silky hairs near the base of the leaf instead of hairs all over. Green foxtail is smaller, with an upright green head and smooth leaves.

Crabgrass grows in the same places but has thin, finger-like seed spikes spreading from a single point, and a papery ligule. All of these are summer annuals, so prevention works the same way for each.

How to get rid of giant foxtail

For a garden or a small patch, pulling is the right call. Foxtail has a shallow, fibrous root and comes out easily when the soil is moist. Hoeing seedlings in June takes care of most of it. The key is to get it out before the heads mature in late summer.

• Mulch and cover: In beds, keep 2 to 3 inches of shredded mulch so seeds in the soil never see light. In vegetable gardens, straw mulch between rows does the same job.
• Thicken the lawn: In lawns, mow at about 3 inches and keep turf dense. Most foxtail in turf is a sign of new seeding or thin, bare areas.
• Preemergence: If foxtail was heavy last year in a lawn, a spring preemergence herbicide containing prodiamine, pendimethalin or dithiopyr, applied before soil temperatures reach about 65°F, stops seedlings. These also stop grass seed, so don’t use them where you plan to overseed that spring.
• Postemergence in lawns: Products with fenoxaprop, quinclorac or topramezone are labeled for foxtails in many cool-season lawns. They work best on young plants before they’ve tillered much.

Always read and follow the product label; the label is the law. Check that it’s labeled for your turf species and for the site, since vegetable gardens and beds need different products than lawns. In Pennsylvania, anyone applying herbicide for hire must hold a PA Department of Agriculture pesticide applicator certification, so if you want a program for the whole lawn, hire a licensed lawn-care company.

Keeping giant foxtail from coming back

Here’s the good news: giant foxtail seed doesn’t last long in the soil compared with many weeds. If you keep it from going to seed for a couple of seasons, the problem drops off sharply.

Cover bare soil quickly after any digging or grading, mulch beds, and pull stragglers before the heads ripen. If you’re bringing in topsoil, ask where it came from, since soil from an old crop field can be loaded with foxtail seed.

Questions we get about giant foxtail

Similar weeds

Yellow FoxtailSetaria pumilaGreen FoxtailSetaria viridisLarge CrabgrassDigitaria sanguinalis