The term “weed” can be applied to any undesirable plant you find growing in your lawn. For example, you may enjoy the early spring appearance of the English daisy dotting the grass, whereas other gardeners might feel it spoils the even texture they would like to have. If you follow the school of thought that a lawn should consist solely of grass, read on.
Lawn weeds should be removed before they have a chance to spread. The two ways to do this are to pull them up by hand or with a tool, or use a chemical spray.
Two effective weeding tools are the screwdriver and asparagus knife. If the lawn is moist, these tools will help you to pry out deep-rooted weeds such as dandelions and plantain, or to lift up weed runners like those on bur clover.
Below you’ll find recommended chemical controls for the common lawn weeds along with some suggestions on how to maintain your lawn to prevent weeds from growing.
Crabgrass. A hot weather annual, crabgrass sprouts in the spring and vigorously spreads its wide leaves, crowding out other grass. When cool fall weather arrives, it turns reddish brown, then dies, leaving its seed in your lawn.One effective non-chemical method for controlling crabgrass is to set your lawn mower at a higher setting; the taller grass prevents sunlight from reaching the crab- grass seeds. A second way is to avoid wearing lawn grass down to bald spots so crabgrass can get a foothold. A third way is to water the lawn infrequently and deeply. The lawn surface will stay fairly dry, cutting down seed germination.
A chemical control for crabgrass is to apply a product containing azac, balan (benefin), betasan (bensulide), or dacthal in winter. Then if any crabgrass sprouts in spring, treat it with a chemical containing amine methyl arsonate, disodium methyl arsonate, or calcium methyl arsonate. Although these chemicals may initially change the color of your grass, this condition is only temporary. Be sure to water the area thoroughly before applying any of the chemicals listed above, then give the grass a second treatment a week later.
Bermuda grass. In hot climates, Bermuda grass grows better than cool season grasses (bluegrass and bent grass). You can encourage its growth by setting your lawn mower at a low setting. This practice weakens other grasses and encourages growth of Bermuda. The only way to kill Bermuda chemically is to apply dalapon to the entire patch of Bermuda repeatedly. Handle dalapon with care because it also kills desirable lawn grasses.
Quackgrass. In cool climates, quackgrass spreads by rhizomes (underground stems that root). Quackgrass also spreads seed heavily; some of the seeds sprout quickly while others lie dormant for years. In addition, quack- grass poisons other grasses. At the first sign of quackgrass, treat the infected areas with a chemical called amino triazole. If quackgrass gets out of hand you may have to have a professional sterilize the ground with a fumigant or sterilant (ask your nurseryman for the name of a contractor who does this work), then plant new grass seed.
Other weed grasses. Many grasses that are too coarse or the wrong color for lawns can be hand-pulled easily. Most of these grasses have dense roots that leave a hole when removed. Dig a little peat moss into the bare patch to bring it up to lawn level, then reseed.
If an unknown lawn weed continues to grow despite removal or chemical treatment, pull up a sampling of the weed and take it to a nurseryman or county agricultural advisor for identification and advice.
Leafy weeds. For spot treatment of leafy weeds use weed oil, but handle it carefully because it will kill any other plant it touches. Applicator sticks containing weedicide can also be used for spot treatment.
Chemical control of leafy weeds consists of spraying on a phenoxy compound that resembles a plant growth hormone, This material is absorbed by the weed, making it grow so fast that it dies. The compound is sold as 2,4-D or 2,4,5-TP. You’ll find 2,4,5-TP more effective for certain weeds such as oxalis or chickweed; check the label for specific directions on how to apply. (Both chemicals will be more effective if you feed and water the lawn first.)
Handle hormone sprays with as much caution as you would insect poisons. Choose a still day for spraying; hormone sprays carried away by a breeze may disfigure or kill other broad-leafed garden plants. Set the sprayer for a dense spray. Avoid hitting your skin and clothing and wash thoroughly after spraying. (Caution: Never use a sprayer that has held chemical hormone sprays for general garden spraying.)
Some lawn fertilizers contain additives for leafy weed control. These fertilizers may be a partial or a complete solution. Read the labels and follow the directions carefully.
