Should I kill crabgrass in late summer or wait for spring?
Killing a heavy crabgrass infestation in mid-September is rarely effective because the plants are already mature and will die off naturally with the first frost anyway. Waiting for the seasonal die-off and applying a pre-emergent herbicide in the spring prevents new seeds from germinating, which stops the endless cycle of trying to salvage a weed-choked lawn by hand.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
- 1scalping the lawn and seeding in the fall while planning to apply pre-emergent in the spring
- 2Applying a healthy dose of weed control
- 3Aerating, seeding, and fertilizing
- 4Mowing at a minimum height of 3 to 3.5 inches
- 5Letting the crabgrass die off naturally during the frost and applying a pre-emergent herbicide in the spring
- 6Manually pulling out the crabgrass during the growing process
- 7Using prodiamine or mesotrione pre-emergent products
- 8having a vendor spread weed killer multiple times
- 9laying partial sod
- 10Heavy dethatching, aeration, and overseeding
- 11Ripping up the worst areas to reseed
- 12Raking in fresh topsoil and a thin layer of peat moss
- 13Top dressing seeds with compost
- 14Mowing at a higher setting (55-60 mm) to protect young grass roots
- 15Considering selective weed killers like Dicophar but waiting for the recommended 6-month establishment mark
- 16Waiting until spring when the growing season is over to address the weeds
- 17Killing the entire lawn with chemicals and starting over
- 18Accepting it and turning the area into a putting green
- 19Spraying Tenacity with a surfactant over multiple applications
- 20giving up and letting the clover thrive
- 21using an iron-based control spray as a defoliant
- 22spraying triclopyr along with a surfactant
In their words
Unedited, most upvoted first, each linked to the thread it came from.
“Realized after mowing in late August that we had so many problem areas - looked like dying poa and just matted thatch buildup.”source ↗
“I can’t believe how many times I detatched a section of the yard (pictured below), but everytime I felt like we were exposing enough soil…it just looked the same the next day!”source ↗
“Located in NJ. like title says, lawn is at least half crab grass. Being mid Sept, does it make sense to kill the crab grass or do I just wait for it to die and add pre emergent in the spring?”source ↗
“I am really struggling to try to make the lawn look nice. Picture is of the front yard and how full it is of weeds, crabgrass, and other stuff.”source ↗
“Still doesn’t look bad but I have peppered crab grass throughout now. I did not put pre-emergent down in the spring.”source ↗
“Should I just scalp, Dethatch, bag, and overseed. Then in the growing process just be adamant on pulling out the crabgrass? Or should I just wait till spring and apply pre-emergent like I should have.”source ↗
“It has been overrun with every kind of weed there is.”source ↗
“In just 6 months I'd say a relatively healthy yard with maybe 10% weed coverage has become more like 85% weed coverage.”source ↗
“Need advice on our lawn and bent grass "infestation."”source ↗
“Is there any other way around this extreme measure?”source ↗
“I’m fighting this battle right now.”source ↗
“Looking to control clover. It’s gotten a pretty big foot-hold in my back lawn this year.”source ↗
“I got so much clover this year I just gave up and let it thrive.”source ↗
“Yea this year it exploded and I’ve heard this from other ppl as well.”source ↗
“The issue is that it isn’t so much “in” my lawn as it is *replacing* it lol. Large areas are getting blanketed out.”source ↗
“Please help! Irish lawn, about 2 months old. I put out seed and fertiliser, and strangely on the bits where I put out fertiliser I now have a crazy amount of docks, with some thistles for good measure.”source ↗
“I have no idea what to do, because I don't want to harm the grass that I've gained, yet I'm afraid that the docks will completely take over and basically destroy all my hard work.”source ↗