When is a good time to apply a pre-emergent crabgrass preventer?
So we never have an “exact” date on when to apply the crabgrass pre-emergent since every season is different. We monitor the weather and soil temperatures. Crabgrass germinates when the soil temperatures are consistently 60° F degrees for 3-5 days at a 1/4″ level. To be effective, crabgrass pre-emergent must be applied at least 2 weeks prior to germination. Here’s a great (real time) link we use for crabgrass germination and optimum times to apply pre-emergent from Michigan State University. GDD Tracker.
As you may know, the best crabgrass prevention is a dense, healthy turf, but because crabgrass has a massive reproductive & survival capability, it is common to have some in your lawn. Some of you may have seen more crabgrass come up several weeks after your first application last year. Here’s a tip: To prevent that second flush, simply apply another crabgrass pre-emergent to your lawn 7 weeks after the first treatment.
Regular fertilization should help thicken turf along with proper watering and mowing. Water deeply and infrequently. (Light and shallow watering will encourage crabgrass growth). Do not mow more than 1/3 of the leaf blade at one time. If you mow below 2.5-3 inches (depending on the turf species) it will increase crabgrass populations.
IMPORTANT TO KNOW: If you are planning on seeding or have completed a dormant winter seeding, we do not recommend using a crabgrass pre-emergent until the new seedlings grow (at least 2 mows at 3 inches high). If you apply it too soon, it will likely end up killing any new grass seedling growth. There are a few options for crabgrass treatment if you have planted grass seed or plan on planting this spring.
For example, a very effective product is a selective herbicide called Tenacity. Tenacity herbicide can be used for pre- and post-emergence control of a wide range broadleaf weed and grass species, including CRABGRASS (well, up to the point where the crabgrass has 4 tillers or fewer).
SOURCE: Kansas State University
Tenacity’s active ingredient, mesotrione, which is based on a naturally occurring compound produced by the bottlebrush plant that inhibits photosynthesis in susceptible plant species. The mesotrione is absorbed by weeds you are targeting through the roots, shoots and leaves and distributed throughout the plant by “translocation“. Because the targeted weeds are blocked from using photosynthesis, it does turn the targeted weeds white, and it may also cause temporary whitening of your turfgrass (for a few weeks anyhow).
Tenacity does NOT contain any fertilizer, so if this is the herbicide you choose, you’ll likely want to also do a non-herbicide / straight fertilizer application (like our 25-0-5 fertilizer) in May. When properly applied, Tenacity will destroy the weed but not harm your grass. And it’s safe to use on established or newly seeded turf.
Just give us a call and we can go over the products to use. Use caution when using post emergent herbicides and ALWAYS read the label. 574-232-6811 is the number to call.
Pick your battles. You shouldn’t plant grass seed AND apply crabgrass pre-emergent at the same time. If crabgrass was a problem for you last year and you want to treat it, apply the crabgrass pre-emergent and save your seeding for fall. That is the best time to seed anyway. (Typically around August 15-September 15 … again, every year is a bit different … Purdue explains more about seeding in their free publication – CLICK HERE).
Here’s more info from Purdue Science: Crabgrass Control
Know when to give up. Crabgrass can be a pain if it is not taken care of early enough. If you wait until summer and you realize your crabgrass is out of control, you may as well let it go until it dies off with the first frost. There are post emergent herbicides that you can use but they are more difficult to use than the pre-emergent products, they cannot be used in the heat of the summer, are expensive, and are only effective on smaller crabgrass plants – which you probably don’t see anyway.
If you are looking for crabgrass pre-emergent + fertilizer, come see us!
We have quality fertilizer in stock at great prices AND you get free expert advice!
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Until next time!
The Red Hen Crew
Article last updated 04/08/24
