Crabgrass is an annual weed, meaning that it sprouts from seeds each spring and dies with the first hard frost each fall. It produces lots of seeds that persist for a long time. Its light green color and coarse, flat texture make it stand out in contrast to the desirable grasses in your lawn. The best way to prevent crabgrass is to keep your lawn thick and lush so the weed seeds have no where to sprout.
What to do now
There's no point in applying any kind of crabgrass treatment now because the plants are mature and will die with the first hard frost which usually strikes by late September in our region. So what can you do now?
The key is to remember that a dense lawn will discourage crabgrass seeds from sprouting and establishing. September is the best month of the year to establish a new lawn and it's the best time to repair and bare spots and get desirable grass species established.
Since the crabgrass plants are going to die soon, now is a great time to get new grass seed established.. By doing so the new grass will have the rest of the fall to thicken up and by next spring your turf should be as dense as possible. Crabgrass seeds don't sprout until early-mid May, a few weeks after your lawn has greened up and thickened.
Steps to Tackle Crabgrass Now
To summarize, here's a process to follow this fall:
1. Set your mower very low to scalp only the areas with crabgrass.
2. Use an iron rake, de-thatching tool or a similar kind of equipment to rip up the remaining crabgrass plants as much as possible and expose the soil beneath. Its impractical to actually pull up the crabgrass plants over a large area, just mangle them as much as possible.
3. Broadcast good quality grass seed and starter fertilizer over the area (perennial ryegrass and fine fescue establish more quickly than Kentucky bluegrass a mixture of all 3 works well.) The packages give you the rates, take time to do the math to apply the right amounts of seed and fertilizer.
4. Apply starter fertilizer wherever you have spread grass seed. The package will identify it as starter fertilizer for lawns.
5. Rake lightly to mix the seed with the soil and to help it settle below existing grass blades
6. Roll entire lawn to press seed into the soil (very important for good germination!)
7. Keep area watered until new seed sprouts (remember, ryegrass and fescue take just a few days to germinate, but Kentucky bluegrass takes 3 weeks)
For more information call our office or visit Cornell's home lawn Web site at www.gardening.cornell.edu/lawn/index.html
Office phone numbers: Clinton County 561-7450, Essex County 962-4810, Franklin County 483-7403.
Visit our local Web site at http://ecgardening.cce.cornell.edu or email your question to askMG@cornell.edu