Annual grass species germinate from seed, complete their life cycle, produce seeds, and die within a year.
Crabgrass is the most common and troublesome weed among annual grass weeds in lawns. Two species, large (hairy) crabgrass and small (smooth) crabgrass, are common in lawns. Other annual grass weeds include foxtails, barnyardgrass, goosegrass, and annual bluegrass. In addition, there are many undesirable perennial grass weeds that infest lawns. Perennial grass weeds such as quackgrass, nimblewill, bromegrass and others can be easily confused with annual grass weeds.
An integrated weed management program is a combination of sound cultural practices and the use of herbicides when necessary. Producing a dense, healthy stand of turfgrass is the first line of defense for controlling annual grass weeds and broadleaf weeds. The proper mowing height and frequency, fertilization and irrigation are part of a sound weed control program and should be practiced throughout the growing season.
Management with Herbicides
Annual grass weeds can be managed with herbicides. Preemergence herbicides provide effective control of crabgrass and other annual grass weeds for several weeks or months, depending upon the product and the rate used. The effectiveness of these materials is based upon their ability to provide excellent weed control with no turf injury.
Timing is important for herbicide application. The best approach is to apply preemergence herbicides before annual grass seeds germinate. If you apply preemergent herbicides after annual grasses emerge above ground, the application will not be as effective.
In general, preemergence herbicides should be applied approximately two weeks prior to the expected weed seed germination period. The best time for annual grass weed control is normally late April or early May in Massachusetts. Herbicides should be watered-in so that the material can form a barrier in the soil prior to weed seed germination. The resulting chemical barrier should not be disturbed during the key weed germination period.
Selective management of germinating annual broadleaf weeds such as chickweed, yellow wood sorrel, and prostrate spurge can be obtained with these preemergence treatments. Preemergence herbicides are generally intended for use only on established turfgrass. Siduron is the only preemergence herbicide that can be used at time of seeding. Quinclorac can be used before seeding or after seeding on seedling turf. Refer to the label of the herbicide selected for information on amount of time between application and seeding of desired grasses, as well as other pertinent information.