One of the most frustrating problems with growing a lawn is managing weeds. Besides making a lawn look unattractive and unkempt, lawn weeds can complete with grass for nutrients and moisture. Although homeowners battle many different types of weeds, some of them are more common than others. It’s important to properly identify a particular weed in order to determine how best to control it.
Crabgrass - Crabgrass (Digitaria spp.) is one of the most typical lawn weeds. The two main crabgrass types are smooth crabgrass and hairy crabgrass. Although they're similar in appearance, the hairy variety has hairs on its leaf, while the other one doesn't. Both are annuals, are coarse in texture and sprout sometime in May. Because crabgrass grows close to the ground, it can escape a lawnmower. Use a crabgrass rake to control lighter populations.
Goosegrass - Goosegrass (Eleusine indica (L.) Gaertn) lawn weeds resemble the shape of a wagon-wheel and have a white centre. They need light and moisture to germinate, do well in compacted soils and mostly compete with turfgrass in thin lawns subjected to heavy traffic. This weed germinates at least two weeks after crabgrass appears. Although the herbicide, Dimension (dithiopyr), can help control goosegrass, don't use this chemical under dry, hot conditions as it's volatile.
Common Chickweed - Common chickweed (Stellaria media), a herbaceous, broadleaved annual, is a spring weed that loves wet, cool conditions. It has smooth, egg-shaped leaves and tender, branching stems. Chickweed flowers grow singularly in small clusters. Their reddish-brown seeds are flat and circular. Because chickweeds form a thick vegetation mat, they can't be eliminated by close mowing. Use timely applications of pre-emergent herbicides such as Simazine and others.
Dandelions - Dandelions (Taraxacum officinaleare) are perennials with fleshy, dense taproots that are able to penetrate 2 feet or more into soil. The top part of the weed has a rosette of leaves that arise from the plant's crown. It's known for its bright yellow, round flowers that grow on a stalk and a seed-head that resembles a puffball of seeds. Control small populations of dandelions by digging or pulling them out. Applying a herbicide is another control method.
Annual Bluegrass - Annual bluegrass (Poa annual) is a bright-green grass that grows vigorously in cool, moist weather. It produces numerous weed seed heads. Patches formed by annual bluegrass can quickly die out with the arrival of hot, dry weather. Control the weed with Glyphosate and use Dacthal in late spring or early fall for any pre-emergence management, advices the University of Delaware Cooperative Extension.
Carpetweed (Mollugo verticillata) - Annual; spreads by seeds; stems grow to 1 foot; found across U.S., except for ND and parts of MT and MN; flowers June through November. Hoe or pull plants when they appear. Mulch deeply to smother any seedlings.
Poison Ivy (Rhus radicans) - Perennial; spreads by creeping rootstock; found across U.S. (not AK or CA) and southern Canada, as vine or shrub; flowers in May and June. Entire plant is toxic. Wear protective gloves and clothing. Cut plant at base, let it dry out, and bury or put vines in trash. Do not compost or burn (inhaling smoke can be fatal). Mulch with cardboard.
Prickly Lettuce (Lactuca serriola) - Annual/biennial; spreads by seeds; height to 5 feet; found across U.S. except southernmost Florida; flowers July through September. Hoe or pull plants as you see them, or cut taproot below soil line. Wear gloves. Attracts beneficial insects and so may be fine for outlying areas, but can play host to lettuce diseases.
Common Cocklebur (Xanthium strumarium) - Annual; spreads by seeds; height to 4 feet; found across U.S. and most of southern Canada, except Quebec and northern New England; flowers August through October. Pull or hoe plants beneath soil line. Can be composted if haven't gone to seed. Use dense mulch to smother seedlings. Thrives in wet soil. Poisonous to livestock; often confused with common burdock.
Canada Thistle (Cirsium arvense) - Perennial; spreads by seeds/rhizomes; height to 5 feet; found coast to coast across northern U.S. into Canada; flowers July through October. Wearing gloves, dig out plants, removing as much root as possible. Cut down new shoots monthly. Mulch with cardboard. Spread corn gluten in early spring to suppress seedlings.