Notice: Your lawn will likely soon be invaded with large, dead patches, especially along streets and driveways and on south- or west-facing hillsides with thin soil and little shade. Chemicals will not solve the problem, at least not this year, so don’t bother calling Dr. Chem and ordering another round of Chem-o-therapy for your lawn.
No, this has been a great summer for crabgrass, and it seems to be growing places that it normally doesn’t. Crabgrass is grass, and this is why you will have no success with selective herbicides.
This fall, while the rest of your lawn stays green even after killing frosts, crabgrass will turn brown for the same reason that it glows green when the rest of your lawn turns brown in mid-summer. In contrast to the rest of your lawn – unless you ordered the plugs of Amazon Zoysia grass from an ad in Parade Magazine – it is a warm-season grass. So in our area, it sprouts late and dies quickly. In contrast to the Amazon Zoysia lawn, however, crabgrass is an annual, so the winter kill is winter kill, and to survive, it must germinate next year on this year’s seeds.
So how do you stop crabgrass?
For now, your only options are weeding: hand-weeding, chemical-weeding, or mechanical-weeding. Hand-weeding will be the least invasive to the rest of your lawn, but the most labor intensive to you. For the future, you need to stop those seeds. You can wait until early next spring to apply a pre-emergent weed treatment (chemical or corn gluten), but this disables any new lawn seeds as well. Possibly the best approach is to use this fall to get a running start on thickening up your desirable turf to leave less room for crabgrass – and other weeds – to sprout next spring.
Now, while we are on the topic of desirable and undesirable grasses, what seed should someone use if overseeding this fall (or seeding anytime)?
1. Unless you know you are seeding toward a specific variety (bluegrass or tall fescue), using a mix is best.
2. Check the label of the mix you buy and avoid products that have tall fescue or a proprietary blend with the word “black” in the name.
“Black” grass will look like there is a shadow on the section of lawn where you use it, and the shadow will last for a few years. Tall fescue is a clump-forming, course-bladed grass that looks like a weed in a fine-bladed lawn, but is as difficult as crabgrass to remove.
3. On the other hand, consider planting a tall fescue lawn if the area has to deal with much sun and traffic.
4. Unless the area is in full sun, use a sun-and-shade mix. If the area is full shade, use shade seed, but expect a mid-summer brownout and weak performance thereafter.
Joshua Arp is an ISA-certified municipal specialist, Clarks Summit’s municipal arborist and an operator of an organic lawn and landscape maintenance business. Reach him at firstname.lastname@example.org.