Weeds are plants you did not select that grow where you do not want them. Weeds compete with lawn grass for sunlight, moisture, space and nutrition. They grow where the grass is not healthy enough to keep them out. Pulling, emergent weed killing chemicals and pre-emergent weed killers help eliminate weeds. The first step in controlling yard weeds is to identify the plant and understand why they are succeeding in your yard. After identification, you can select the best control methods.
The two largest categories of lawn weeds are broadleaf and grassy. For removing or controlling weeds, it is less important to identify the specific weed type than it is to identify which large category it belongs to because the control methods are different.
Grassy weeds have blade type leaves and appear similar to the planted grass. Grassy weeds may be divided into bunchers and spreaders. Bunch grasses have a single clump of blades that grow in size if not removed. Common bunch grasses are dallisgrass, crabgrass, orchardgrass, nimblewill, and tall fescue. Bunch grasses increase their share of your yard by spreading seeds.
Spreaders as the name implies produce above-ground stems or runners called stolons or below-ground stems called rhizomes that spread the weed throughout your lawn. Although a desirable grass in some locales, bermuda grass may be a spreading weed in turf lawns in the North. Quackgrass, another troublesome grassy weed, spreads underground through its roots as well as producing seeds.
In general, a broadleaf weed is any weed that is not a grass. Common broadleaf weeds include dandelions, chickweed, purslane, henbit and clover. Over 100 types of broadleaf weeds grow in yards across the United States. Broadleaf weeds may be perennials, annuals or winter annuals.
The most effective way to control weeds in your yard is to maintain a healthy stand of desired grass. St. Augustine, Bermuda, bluegrass, and fine fescue are examples of desirable grasses depending on the area of the country. Providing fertilizer and adequate moisture helps your grass successfully compete and fight-off invading grasses and weeds. New lawns should be seeded with grass that is certified weed-free. Sodded lawns should be checked for weeds before the laying the sod.
Pre-emergent weed control products stop weed seeds from growing. They are granular products that control annual grassy weeds by inhibiting root system cell division. Pre-emergent weed killers do not work on weeds that are actively growing. Apply a pre-emergent weed control in your yard before the weeds are growing. In the Northern U.S., early spring is the time to use a pre-emergent. In the warmer South, fall is the best time to apply for winter weeds.
Broadleaf weed control can be selective or non-selective. The herbicide glyphosate, found in Roundup, is an example of a non-selective weed control that kills any plant it touches including your desired yard grass. Spot use of glyphosates leaves a dead area in the yard that can be filled in later with seed or sod.
Selective broadleaf weed control removes certain kinds of weeds while not harming the surrounding turf grass. For bermuda or zoysia lawns, weed killers with MSMA or DSMA often provide a wide spectrum of selective control. 2,4-D is an active ingredient in many herbicides that provides effective broadleaf weed control for most types of yard grass. However, these products are not to be used on St. Augustine grass. If your lawn is St. Augustine, be sure to read package directions on any weed control product to make sure it is safe for use on your grass.