The best defense against weeds that take over the lawn is to maintain your lawn as a dense and vigorously growing turf. Weeds, especially those that can take over a lawn, are often an indication that an underlying problem may need to be addressed and corrected to completely eradicate the weed problems.
Dandelions, plaintain, purslane, clover and thistle are just some of the many broadleaf weeds that can take over the lawn. Treat these weeds using selective post-emergence herbicides. Apply them in early fall to control perennial and winter-germinating annual broadleaf weeds and in spring to control spring-germinating annual broadleaf weeds. The best results are obtained when post-emergent herbicides are applied when the soil is moist and the weeds are young and in active growth.
Annual Grass Weeds
Annual grass-like weeds such as annual bluegrass, crabgrass and foxtail are best controlled using a pre-emergent herbicide. It should be applied to the lawn at least two to three weeks before the annual grass weeds are likely to germinate, usually in mid spring. Do not use pre-emergent herbicides on newly seeded lawn as it will also kill the desired grass seed.
Perennial Grass Weeds
Quackgrass, tall fescue and creeping bentgrass are all perennial grass-like weeds that can be controlled only with a non-selective herbicide, which means it will kill all vegetation it comes in contact with. Spot treat individual weeds when they are in active growth and take care not to let the herbicide come in contact with your turf grass.