Weeds are simply plants that grow where we do not want them to. An attractive Indiana lawn should consist of the same type of grass throughout. This gives the lawn a smooth appearance after mowing. It also means that the grass will grow at the same pace throughout the lawn, making maintenance easier to schedule. Some native Indiana grasses intrude as weeds into seeded lawns, and they spoil the appearance of the turf. They also use up the water and nutrients that the surrounding lawn grass needs.
Foxtail (Alopecurus sp.) is a native Indiana grass. It is a coarse, bunching grass that detracts from the appearance of a lawn, even after mowing. Foxtail is an annual that grows from seed each spring. It does not appear until late spring or early summer, because it requires temperatures between 68 and 95 degrees for germination.
The most effective chemical treatment is a pre-emergent applied early in the spring before the seeds germinate. Eradication treatments later in the growing season give poor results on foxtail. Organic pre-emergent treatment uses corn gluten sprinkled on the lawn before the seed germinates. As a bonus, corn gluten also adds nitrogen to the soil, which gives the lawn a boost. Nitrogen applications that help the rest of the lawn can hamper the growth of foxtail. A healthy, thick lawn can actually choke out foxtail, which depends on a small patch of open soil for the seeds to germinate. Regular mowing to keep seedheads from forming will interrupt the foxtail life cycle.
Yellow nutsedge is not a grass and it is not a broadleaf. Sedges are classified in the family Cyperaceae. Yellow nutsedge is a perennial that reproduces by tiny tubers called nutlets, and by rhizomes. Nutsedge is easy to identify, because its stems are triangular. Roll the stem between your thumb and fingers, and if you feel the "corners," it is nutsedge.
Yellow nutsedge grows above the surface of the lawn, so it is easy to spot. If you see only a few plants, hand-pulling is the easy way to control it. You may want to loosen the soil with a small garden fork before pulling to make sure you get the tiny tubers. Nutsedge needs light and space to grow, so by keeping your lawn grass thick, it can crowd out competing weeds.
Crabgrass (Digitaria sp.) is a low-growing plant with long stems that spread in all directions like the legs of a crab. It grows in full sun, and will not grow in shade. Crabgrass is an annual that produces from mid-summer until frost. It is a lighter color that lawn grasses, so it stands out against a green lawn. The first crabgrass seed germinates in early May in Indiana.
Pre-emergent weed controls are effective in preventing crabgrass. Chemical treatments are available. The organic pre-emergent alternative, corn gluten, is a very effective option for crabgrass. It should be applied before the seeds germinate, when the soil temperature is not above 50 degrees F.