As most of you are WELL aware of, crabgrass is a common summer annual weed in our Michiana lawns. In July, crabgrass plants were busy flowering and spreading their seeds, but each year it will die out naturally after the first frost.
But what can you do about crabgrass in the months between July and October/November when we usually see our first frost?
Unfortunately, the best time to control late summer / early fall crabgrass is to go back in time and deal with it in THE SPRING with a PRE-EMERGENT herbicide (like our 13-0-5 Fertilizer + Crabgrass preventer), along with mowing right, watering right, and fertilizing right.
Crabgrass is tough to kill and reproduces very effectively. To expect a 100% crabgrass-free lawn is probably not very realistic – Mother Nature has the upper hand. The most effective approach to controlling this weed is to nurture and maintain a dense, healthy lawn to out-compete crabgrass (and other weeds by default), and prevent it from establishing in the first place.
We’ve been getting quite a few calls and visits from customers whose lawns are mostly free of this weed EXCEPT along areas like the edges along sidewalks, driveways, and roads. These sections have two major issues going against them:
(1) SALT from winter that is still hanging around in the soil; and
(2) COMPACTION from things like foot traffic, auto/mower tires, and piled snow.
Crabgrass – among other weeds – is very tolerant of growing where there is salt and compaction. Turf grasses are sensitive to both salt and compaction, and tend to NOT grow well in these spots. Kentucky bluegrass is especially sensitive to salt damage, while perennial ryegrass, fine fescues, and tall fescue are more tolerant, but not totally resistant.
Another common trouble-spot is along the seams where sod was laid but the edges of the rolls were probably not placed close enough together. The turf growing in these seams is thin and weak, allowing weeds to out-compete your grass.
Again, the crabgrass you see now in late-August WILL die off with our first frost. But what about using a POST-emergent herbicide? There are effective products to use, but TIMING is everything and ALWAYS READ THE LABEL. Common to these post-emergent crabgrass herbicides is that you need to apply them when the plant is YOUNG … and, well, once we get past mid-July the crabgrass plants are usually
too large to control effectively. Another challenge to treating crabgrass that has already shown up is that these post-emergents work best at temperatures below 85ºF on clear days with low humidity. That’s pretty hard to do in the dog-days of summer!
So what do I do this time of year in my own yard? I pulled a few out of my front yard the other day. I have more in the backyard and I plan on leaving them. I am not going to try to attempt to eradicate them with herbicides at this time. They are very big and tougher to kill. I am going to tolerate them because they will die with the first frost. Every year I tell many customers that you can apply Crabgrass preventer 2 times in a year. If crabgrass was bad this year, I would look to doing better prevention next year.
On the other hand, if you’re up for the challenge, we do carry some post-emergent herbicides that we’d be happy to educate you about.
For more in-depth, science-based information, check out Purdue Extension’s publication, “Control of Crabgrass in Home Lawns” by CLICKING HERE.
As always, give our team a call if you have any questions – 574-232-6811.
— Jeremy and the Red Hen Turf Farm Team