Grassy weeds like crabgrass are the bane of every homeowner’s existence.
Crabgrass not only makes your lawn look unsightly, but it spreads very quickly.
Without proper crabgrass control measures, the grassy weed will take over your entire lawn in a short amount of time.
By using a crabgrass pre-emergent herbicide, you will be able to stop the weed before it germinates.
Timing is crucial when applying a crabgrass preventer because you want to ensure it reaches the soil.
So, can crabgrass preventer be applied to wet grass?
Applying crabgrass preventers on wet grass is safe if the herbicide makes it into the soil. Liquid crabgrass preventers will automatically wash down into the soil, but granular crabgrass preventers will stick to wet leaves and need to be rinsed off.
If granular crabgrass preventers are not rinsed from wet grass blades, they will not be effective at weed control.
Crabgrass preventers must also be applied at the right time of year to work correctly.
Read on for tips on applying crabgrass preventer and learn what might cause the pre-emergent herbicide to fail.
Tips for Applying Crabgrass Preventer at the Right Time
Perfect timing is everything when applying crabgrass preventer to your lawn.
Since crabgrass preventer is a pre-emergent herbicide, it will only stop seeds from germinating.
If you have existing crabgrass weeds on your lawn, you must use a post-emergent herbicide to kill them.
Below are some tips for applying crabgrass preventer at the ideal time.
Further Reading: Getting Rid of Crabgrass Tips and Tricks
Apply in Early Spring
Crabgrass seeds are dropped in late summer to fall and stay dormant in soil throughout the winter.
The crabgrass seeds will germinate in the spring as temperatures get warmer.
Applying a crabgrass preventer in the early spring stops seed germination.
The perfect time to apply crabgrass preventer to your lawn is between late March and early April.
Ensure the Soil Is Warm
Seeds need warmth to activate the enzymes necessary for stimulating germination.
The ideal ground temperature range for crabgrass seeds to begin germinating is between 55 to 60° degrees Fahrenheit (16° C).
Soil temperatures are affected by several factors, including wind, air temperature, and the amount of sunlight on your lawn.
To get an accurate reading on ground temperatures in your lawn, use a clean soil thermometer to check daily temperatures beginning in early March.
Look for consistent soil temperatures of at least 55° degrees Fahrenheit (13° C) or higher for several days in a row and no danger of a late frost.
It is time to apply a crabgrass preventer when these conditions are met.
Most crabgrass weed seeds will begin to germinate at these soil temperatures.
The pre-emergent herbicide will halt the germination process of the crabgrass seedlings.
This allows you to control the crabgrass weeds for the upcoming growing season.
Apply Before Rainfall
The optimal time for applying a crabgrass preventer is before it rains.
Rain washes crabgrass preventer into the soil.
This is great!
It prevents the seeds from germinating and developing roots.
Look for dry conditions in your weather forecast when it is time to apply the crabgrass preventer.
You will need to thoroughly water your lawn after application if this is the case.
For the best results, your lawn will need 1/4 to 1/2″ inches of water within 2-3 days of crabgrass pre-emergent application.
When the crabgrass preventer is applied without watering or rainfall, the herbicide will be less effective because it will break down.
Follow the instructions on the product label.
It will ensure your lawn is getting the correct amount of water after crabgrass preventer application.
Most liquid herbicides need not be watered to be effective, but granular products must be washed into the soil.
Applying the crabgrass preventer in extremely wet conditions may cause the herbicide to dissolve or run off your lawn.
This will render it ineffective.
If heavy rains wash away the herbicide, you may need another application of crabgrass preventer for adequate coverage.
When the ground has been soaked by consistent rain, wait for the ground to dry out before applying the crabgrass preventer.
How Long Does a Crabgrass Preventer Last?
Most long-term crabgrass preventers are effective in the soil for anywhere from 2 to 6 months.
A crabgrass preventer like this one will keep crabgrass weed seeds from germinating for up to six months.
Applying a crabgrass preventer twice yearly is usually recommended to offer complete protection.
The second application is typically applied in early summer, around 3-4 months after the first application.
You must wait for a minimum of two months between pre-emergent herbicide applications.
Do not apply a crabgrass preventer within 6-8 weeks of overseeding or planting new grass.
The herbicide may prevent your grass seeds from sprouting.
Always read the label on the pre-emergent herbicide you are using to ensure it will not damage the type of grass on your lawn, and follow the application instructions carefully.
If crabgrass is already growing in your lawn, you will need a post-emergent herbicide, such as this one on Amazon, to kill the existing weeds.
Most herbicides for killing crabgrass will also eliminate broadleaf weeds like dandelion and clover.
What Causes a Crabgrass Preventer To Fail?
If the crabgrass preventer is somehow diluted or breaks down, the crabgrass seeds will be able to germinate and sprout into weeds.
There are several reasons this issue might occur, but there are ways to prevent it.
If you are experiencing drought conditions, your soil may become dry enough to crack.
Crabgrass weed seedlings are persistent and will grow through these cracks in the dry soil even when there is little moisture in the ground.
To prevent the ground from completely drying out, you must irrigate your lawn at least once per week with a half-inch of water.
When you water the lawn less frequently, it is best to soak the soil.
Giving your lawn a good soak at least once per week is more effective than watering just a little daily.
It may not be enough to keep your grass from going dormant, but it will supply your soil with enough moisture to prevent it from drying out entirely.
Any soil disturbances in areas treated with a crabgrass preventer will break the herbicide’s barrier and allow crabgrass weeds to grow.
If you need to dig up part of your lawn, you must reapply the crabgrass preventer to the area for it to be effective.
During periods of heavy rain or overwatering your lawn, the crabgrass preventer will become diluted.
The herbicide barrier will break down early, and you will have crabgrass growth late into the growing season.
Avoid overwatering your lawn; if your area has received excess rainfall, it will be necessary to reapply a crabgrass preventer.
Uneven crabgrass preventer application or a failure to apply the proper amount according to the product label will cause the herbicide to be less effective.
Following a few basic steps makes it easy to avoid improper herbicide application.
You will need a sprayer to apply a liquid crabgrass preventer.
Be sure to follow the application rate on the herbicide product label and calibrate your sprayer accordingly.
For granular crabgrass preventer application, you will use a spreader.
Adjust the settings on your spreader according to the instructions on the herbicide label.
Granules do not have to be watered in, but the herbicide will be more effective if your lawn receives between 1/4 and 1/2″ inches of water within 2-3 days.
The water washes the granules from the grass blades and allows the herbicide to penetrate the soil, creating a barrier against weeds.