With all of the rainfall this winter, we are likely to see an explosion of weeds this spring in home lawns. Crabgrass is one of the most common lawn weeds and fortunately one of the easiest to control.
Much of this battle with crabgrass and many other weeds in the lawn can be won simply through timing a pesticide application. You must understand and identify the weed species before you can be successful with a control program. Is the weed warm or cool season, and is it an annual, biennial or perennial?
Crabgrass is a summer annual. This simply means that it germinates in the early spring from seed, grows, produces a seedhead, and then it dies when frosted on in October. It must then germinate again the following spring. Another weed common in home lawns is Bermuda grass. This weed is actually a summer perennial that emerges in the spring from an established root system, grows throughout the summer and then goes dormant after frost in the fall. Its root system grows each year and persists in the soil throughout the winter. A biennial, although less common in the home lawn, has a two-year life cycle where the plant will grow leaves in the first year, turn dormant in the winter, reemerge the second and flower.
Let us get back to gaining control of the crabgrass in your lawn. There are many crabgrass preventative materials on the market. Selection of a particular pesticide brand is usually not important, but application timing is critical. You will need to watch forsythia shrubs to know when to apply the herbicide. The best timing mechanism for crabgrass control is to apply a crabgrass preemergent when you see the first yellow bloom.
Applying the crabgrass preemergent at this time will prevent the establishment of crabgrass for approximately eight weeks. A follow-up application about eight weeks later will be essential to prevent the crabgrass for the full 120-day germination period into mid-July. This application will also control the goose grass and some other annual weeds in your lawn.
An herbicide, Quinclorac, is available to apply over the top of established crabgrass. This material is a liquid and will be more difficult to apply than the granular crabgrass preemergents.
Remember to watch for the forsythia bloom in the next few days.
Chris Ramsey is an agriculture extension agent at UT-TSU Extension in Sullivan County. His office is at 140 Spurgeon Lane, Blountville, TN 37617. You can reach him at 423-574-1919 or firstname.lastname@example.org.