Apply crabgrass preventer to Wisconsin lawns in spring, when the soil temperature rises to 55℉ for 3 consecutive days. This typically occurs in mid-April. In order to get the best crabgrass prevention results, follow these guidelines:
- Apply when Spring soil temperatures reach 55℉ (typically mid-April)
- Use a high-quality crabgrass preventer.
- Apply using a broadcast spreader or seeder.
- Water crabgrass preventer into the soil after application.
- Do not seed your lawn less than 6 weeks after applying crabgrass preventer.
- Kill any crabgrass that emerges using a lawn-safe crabgrass spray.
By timing your crabgrass preventer application, using the right products for the job, and following guidelines for optimal application, you will prevent crabgrass from sprouting on your lawn.
Table of Contents
Why Soil Temperature is Key to Crabgrass Preventer Timing
Crabgrass preventers are pre-emergent herbicides. This means they kill seeds just as they begin to sprout underground. A crabgrass preventer won’t kill dormant seeds or mature crabgrass. So, for your crabgrass preventer to be effective, it should be applied when crabgrass seeds are just beginning to germinate in spring.
Crabgrass seeds germinate when soil temperatures reach 57℉. In order to make sure you stop crabgrass in its tracks, begin applying your crabgrass preventer once soil temperatures climb up to 55℉ in spring. Once you apply your crabgrass preventer and water it in, it will remain active and kill crabgrass seeds for about 6 weeks.
How to Check Your Soil Temperature for Free
There’s no need for soil thermometers or specialized tools. Simply use this free soil temperature map to check soil temperatures in your area. Although your yard may have slightly different soil temperatures due to shade, wind exposure, and other factors, this map is accurate enough for crabgrass preventer application.
Remember, the soil temperature is not the same as air temperature. Soil temperatures are typically around 10 degrees cooler than daytime air temperatures.
Average Timing for Crabgrass Preventer in Wisconsin
Most lawn care experts ballpark mid-April as the best date to apply a crabgrass preventer in Wisconsin. This is only a generalization, however. Temperatures and timing vary from year to year.
Following a mild winter, soil temperatures may reach optimal levels in late-March. Meanwhile, if there is a cold winter, or if you live in one of the northernmost portions of Wisconsin like Wausau or Superior, your soil may not reach the right temperature for pre-emergent herbicide application until late-April.
Best Wisconsin Crabgrass Control Products
Scotts WeedEx is one of the best crabgrass preventers on the market. It comes from a tried-and-true company that consistently provides great value at an affordable rate.
Preen is another highly effective product proven to stop crabgrass in spring. It is one of the most powerful pre-emergent herbicides on the market.
If you are planning to fertilize your lawn in spring, try Scotts Turf Builder/Crabgrass Preventer. It combines crabgrass preventing herbicide with fertilizer. Applying both at once is more cost-efficient and allows you to complete two jobs at once.
Natural Crabgrass Preventer
If you do not want to use chemicals on your Wisconsin lawn, try an all-natural crabgrass preventer, such as Espoma Weed Preventer.
This natural crabgrass preventer is made from 100% Corn Gluten Meal. This corn byproduct can be applied at the same time as a chemical crabgrass preventer. It works by absorbing moisture, drying out seeds as they sprout, killing them. It’s an organic alternative to chemical products.
How to Apply Crabgrass Preventer in Wisconsin
Once you have chosen your crabgrass preventer product and the soil temperature is ripe for application, follow these steps to ensure you obtain the best outcome.
- Wait until spring soil temperatures have risen to 55℉ for 3 consecutive days.
- Crabgrass preventer usually comes in pellet form. Load it into a broadcast spreader for even distribution.
- Follow label instructions to apply the manufacturer-recommended amount of crabgrass preventer per square foot of lawn.
- For even coverage, spread the crabgrass preventer going first in an east-west pattern, then in a north-south pattern.
- After application, water crabgrass preventer into the soil with 1/2 inch of water (about half an hour with a sprinkler).
Unlike most herbicides, crabgrass preventer must be watered into the soil, either with a sprinkler or by rainfall. This is because crabgrass preventer must seep into the soil and form a barrier that kills crabgrass seeds as they sprout.
Will Crabgrass Preventer Hurt Grass Seed?
Crabgrass preventer will prevent all seeds from sprouting. This includes any and all grass seed. The good news is that Wisconsin lawns thrive best when overseeded in fall, not spring. When creating your lawn care calendar, pencil crabgrass preventer in for spring and grass seeding in for early fall.
- Do not apply crabgrass preventer if you have seeded your lawn in the past 4 weeks.
- Do not apply crabgrass preventer if you plan to seed your lawn in the next 6 weeks.
- Plan to apply crabgrass preventer in spring, then seed your lawn in fall.
The fact that crabgrass preventer stops every type of plant from sprouting can be used to your benefit. When spreading crabgrass preventer, it’s often beneficial to also spread the product in gardens with established plants. The crabgrass preventer will stop weeds from sprouting there but won’t harm any mature plants.
What to Do if Crabgrass Preventer Fails
Maybe it’s too late in the year for a crabgrass preventer, or maybe some stubborn crabgrass survived the pre-emergent application in your yard. No matter the case, you can still attack the crabgrass growing in your yard without killing your grass.
- Spray with a lawn-safe weed killer containing Quinclorac, such as Orth Weed-B-Gon Plus Crabgrass Control.
- Hand-pull crabgrass in your yard.
- Mow your grass at 3–3.5 inches in height, to allow your lawn grass to grow tall enough to shade out crabgrass.
If you have applied your crabgrass preventer at the right time, most, if not all, of the crabgrass will be prevented from sprouting. If some does appear, it will be in much lower amounts than if you didn’t use a crabgrass preventer. This makes the invasive crabgrass a lot easier to manage.
Best Time to Apply Crabgrass Preventer in Wisconsin
Crabgrass preventer is most effective when applied in spring, as soil temperatures rise to 55℉. In Wisconsin, this typically occurs around mid-April. Times may vary for lawns in southern Wisconsin versus northern Wisconsin, so measure the temperature of your soil for the best results.
When the time is right, apply your crabgrass preventer using a seed spreader for even coverage. Then, water the crabgrass preventer into the soil. The pre-emergent herbicide in the crabgrass preventer will remain in the soil for up to 6 weeks, killing any crabgrass seeds as they sprout.