Lawn grass weeds can be a nuisance for any homeowner or backyard gardener, with millions spent each year on products such as herbicides and other weed control methods. While some grass species may be just what one homeowner wants, others may consider it to be a nuisance weed. Aggressive grass types include crabgrass, annual bluegrass, Bermuda grass and dallisgrass. These grass weeds may appear at different times of the year and be treated in different ways.
If you are having trouble identifying the type of grass weeds you have, keep in mind that seasons often bring different grass types. For example, some grasses may appear in the spring when the weather is cool and others may appear during the summer. These are often referred to as cool-season grasses and warm-season grasses. Tall fescue and orchard grass are examples of cool-season weeds. Crabgrass and Bermuda are warm-season weeds. You may find that the simplest solution is simply to see what your neighbors are growing and compare it to what is intruding onto your lawn.
Many lawn weeds are able to take advantage of grasses that have become distressed or are otherwise unhealthy. Therefore, the best way to prevent an incursion of weeds is to keep your lawn full and healthy and cut at the highest recommended height. Because most weeds prefer locations with little competition for resources and bright areas, these simple steps can go a long way toward a great-looking lawn.
One of the most important things you can do to come up with an effective plan of action against any weed species is to accurately identify it. Some are annuals and some are perennials. If they are annuals, for example, they can be controlled with a pre-emergent herbicide before they emerge each year. Perennials will require a post-emergent herbicide or other method.
The vast majority of grass weeds favor bright, sunny conditions, whether they are cool-season or warm-season grasses. Therefore, covering the grass with newspaper, black plastic or some other type of opaque product should help. Grass depends on photosynthesis to provide sugars needed for life. Without light, photosynthesis cannot happen and the life cycle will be dramatically reduced.
Some weeds will not look like grass and instead are referred to as broadleaf weeds because they have larger leaves reminiscent of other types of plants. These weeds can still choke out desired grass species and have an unflattering look in a lawn. Broadleaf herbicides can be used on these types of weeds without any harmful effects on existing grasses. Common broadleaf weeds include dandelions, clover and chickweed.
Though it may sometimes be necessary, using a non-selective herbicide will likely destroy all plant material in the area it is applied. Thus, even desired species could be adversely affected by the action. If possible, spray such herbicides only in areas where the undesired species exist. If this is not possible, then be prepared to replant a desired grass species within a month or two of the herbicide application.