How To Control Crabgrass

Controlling Crabgrass

With Atlanta thawing and the heat rolling in, this means weeds are coming back to life. This always means the dreaded and stubborn crabgrass. With some prevention and determination, you can prevent this aggravating intruder from totally taking over your lawn.

Preventing Crabgrass

The warm summer months is when crabgrass is most active and spreads the most. Each plant produces thousands of seeds between midsummer and early fall. While the first frost kills off the crabgrass, the seeds remain dormant. Now that the temperatures are rising, the seeds are beginning to grow. The secret to eliminating crabgrass is making sure that the seeds don’t germinate. This can be done several ways:

  • Check the recommended mowing heights for your type of grass and cut your lawn at the highest recommended setting. Crabgrass needs plenty of light to germinate, so keep the your grass as thick and long as possible to ensure there is shade near the soil surface.
  • Remove no more than one-third of the grass blade at one time when mowing. Mow at frequent intervals to keep the grass a fairly consistent length. Scalping your lawn produces patches where crabgrass and other weeds can germinate.
  • Water in long, heavy intervals rather than shallow, frequent ones. Watering on an irregular schedule only when needed promotes deeper root growth that’s essential to healthy turfgrass. If your lawn has been seeded recently, water in shallow, more frequent intervals until the grass gets established. Remember that most established lawns require one inch of water per week from rain or irrigation.
  • At least once a year, fertilize your grass.

Dealing with established crabgrass.

If the crabgrass has already become established in your lawn, the aforementioned maintenance may not be enough. The next line of defense when it comes to crabgrass is pre-emergent herbicide. These herbicides kill the crabgrass seedlings as they are germinating. When you apply this always follow the instructions on the label. However the general guidelines are as follows:

  • Timing is key when using pre-emergent herbicides. Application times depend greatly on weather patterns, which vary depending on where you live.
  • Apply the herbicide when the ground temperature rises above 60 degrees. Since it’s difficult for most of us to monitor the soil temperature, there’s an easier way. When you notice shrubs blooming and trees budding, this is the time to apply the herbicide. Warm nights and periods of rainfall encourage crabgrass germination. If your weather fits this pattern, get the herbicide in place right away.
  • For newly-seeded lawns, wait until you have mowed your lawn three times before applying the herbicide to avoid killing the new grass seedlings.
  • Apply the herbicide uniformly across your lawn. If a spot is missed, crabgrass can get established and then attack the rest of your lawn.
  • Do not de-thatch or aerate the lawn after applying the herbicide. Doing so may break the chemical barrier of the herbicide.
  • Wait two to four months to re-seed the lawn after using a pre-emergent herbicide.
  • Do not use a pre-emergent herbicide if crabgrass is already in the lawn or if you have just installed sod.
  • Use a pre-emergent herbicide during the late winter or early spring of the next year to prevent any crabgrass seeds left behind from developing at their next opportunity.