Fall Panicum
Home / Weed identification / Fall Panicum
Pennsylvania weed ID · Grassy weed
Fall Panicum
Panicum dichotomiflorum · Poaceae (grass family)
- Summer annual
- Grass
- Native
If a coarse, smooth grass with a white stripe down each leaf shows up in your thin lawn or garden in midsummer and throws out big airy seed heads by fall, it's fall panicum.
How to get rid of itAll weeds A–Z
What is fall panicum?
Quick fall panicum identification helps because people often lump it in with crabgrass. It’s a native summer annual grass that sprouts from seed in late spring and summer, grows fast, and dies at the first hard frost.
In farm fields it can grow chest-high. In a mowed lawn it stays low and spreads out, forming coarse, light-green clumps that stand out against bluegrass and fescue. It’s mostly a problem in thin turf, new seedings and gardens with bare soil.
The name throws people off. It doesn’t sprout in fall; it just shows off in fall, when those big, airy, purplish seed heads stand above everything else in a field or garden edge. By then, the damage for next year is already being done, so the real work happens in spring and early summer.
Fall panicum identification: what to look for
Fall panicum looks smooth and a little shiny compared to most weedy grasses. The best clues are in the leaves and stems.
- Leaves: Smooth and hairless on mature plants, with a wide, bright white midrib running down the center. Edges are often tinged red.
- Stems: Thick and waxy, often reddish-purple near the base. The stems bend at the swollen joints, giving them a zigzag look.
- Ligule: Bend a leaf back where it meets the stem and you’ll see a short fringe of hairs. There are no auricles.
- Seed heads: Large, open and branched, turning purplish in late summer and fall. That’s where the name comes from.
- Seedlings: Often purplish, with hairs on the underside of the first few leaves that disappear as the plant matures.
Where it grows in Pennsylvania
Fall panicum is common across Pennsylvania in cropland, gardens and disturbed soil. It likes warm, moist ground and will put up with soil that’s compacted or poorly drained, places where lawn grasses struggle.
In central PA yards, look for it in new lawns seeded in spring, along driveway and sidewalk edges where turf is thin, in bare spots after construction, and in vegetable gardens. River-valley soils that stay wet into summer suit it well.
It also moves around with soil. Fill dirt, topsoil brought in for a project, and mud on equipment can all carry seed into a yard that never had it before.
Fall panicum look-alikes
It’s usually mistaken for large crabgrass. Crabgrass is hairy on the leaves and sheaths and has a papery, membranous ligule. Fall panicum’s mature leaves are smooth, with that white stripe and a hairy-fringe ligule.
Foxtails have similar timing but form dense, bristly, bottlebrush seed heads, and yellow foxtail has long wispy hairs at the base of the leaf. Barnyardgrass is another summer annual, but it has no ligule at all, which is an easy check.
How to get rid of fall panicum
Because it’s an annual, each plant dies at frost on its own. Your goal is to keep it from dropping seed and to stop next year’s crop from sprouting.
- Pulling: A few clumps in a lawn or garden are easy to pull or dig, especially when the soil is moist. Get them before seed heads form.
- Mowing: Regular mowing keeps it from producing full seed heads, though plants in a lawn can still set some seed close to the ground.
- Garden cultivation: Shallow hoeing kills seedlings easily, and a layer of mulch blocks most new ones.
- Preemergence: Lawn preemergence herbicides with prodiamine or dithiopyr, applied in spring before it sprouts, are commonly labeled for fall panicum along with crabgrass. Don’t use them where you plan to seed grass.
- Postemergence: Fenoxaprop is labeled for panicum species in many cool-season lawns and works best on young plants. Some common crabgrass killers, like quinclorac, aren’t reliable on fall panicum, so check the label.
Always read and follow the product label (the label is the law), and make sure the product is labeled for your lawn type and site. Applying herbicide for hire in Pennsylvania requires a PA Department of Agriculture pesticide applicator certification, so bigger jobs go to a licensed lawn-care company.
Keeping it from coming back
A thick lawn is your best defense, since fall panicum needs bare soil and sunlight to get started. Mow at three to three and a half inches, fertilize in the fall, and overseed thin spots in late summer once the panicum has died back.
Loosening compacted soil with core aeration and fixing areas that stay wet both help your grass outcompete it. In gardens, keep soil covered with mulch or a crop, and pull late plants before they seed.
Remember that the seed doesn’t last as long in the soil as some weedy grasses do. If you keep plants from going to seed for a few seasons in a row, you’ll see noticeably fewer each year.
Questions we get about fall panicum
Is fall panicum the same as crabgrass?
No. Both are summer annual grasses, but fall panicum has smooth leaves with a white midrib and zigzag stems, while crabgrass is hairy and has a papery ligule.
Will my crabgrass preventer stop fall panicum?
Many lawn preemergence products with prodiamine or dithiopyr list fall panicum on the label, but check your specific product. Timing matters too, since it sprouts a bit later than crabgrass.
Is fall panicum a native plant?
Yes. It's native to North America, but it still acts as a weed in lawns, gardens and crop fields.
Weeds taking over a bed, slope or wet spot?
If bare, compacted ground keeps filling with summer grasses, Muthler can regrade and reseed or sod the area so you have a thick lawn instead. We rebuild beds, regrade and drain wet ground, clear overgrown brush and build patios and walls across Clinton, Lycoming, Centre and Union counties.
Get a free estimate(570) 397-9800Similar weeds
Further reading: Penn State Extension
Herbicides: always read and follow the product label. Applying pesticides for hire in Pennsylvania requires PA Dept. of Agriculture certification.