How Long Does Prodiamine Last?

Prodiamine can be found as the active ingredient in many weed control formulas targeting crabgrass and other annual weeds. It can also be purchased in a fine granular form that’s mixed with water and applied as a liquid, notably sold as Barrier and Prodiamine 65 WDG (water dispersible granular). 

When the time comes to apply pre-emergents in the late winter, early spring, or early fall, the amount you put down, and when, determines how long the herbicide will be effective. For Prodiamine, this may be anywhere between 2 and 8 months, based on the amount that you put down.

How Does Prodiamine Work?

Prodiamine is an herbicide used to prevent seeds of unwanted plants from germinating. The herbicide is applied in a liquid form, then soaks into the ground to create a barrier in the upper topsoil that prevents any germinating seeds from successfully growing roots, stopping the plant from sprouting or emerging from the surface.

The herbicide is usually used for grassy and annual weeds that sprout from seed each year. This is in contrast with most broadleaf weeds, like clover and dandelion, which are perennial weeds that regrow each year from established roots. Post-emergent formulas are used to target broadleaf weeds to get rid of both the plant and the roots.

Quali-Pro Prodiamine, Pre-Emergent Herbicide, 5 lbs, Yellow Granules

Since weed seeds are prevented from sprouting, your grass doesn’t have competition when it grows back out of dormancy, allowing the grass to fill in all the open space in the yard. When the lawn revives and regrows a dense turf, it’s healthier and fewer weeds are able to grow throughout the season. Since weeds not only compete for space but also moisture and nutrients, a weed-free lawn shouldn’t need as much fertilizer or herbicide applications later in the year. 

When Should Prodiamine 65 WDG Be Applied?

Prodiamine should be applied in the early spring or early fall before crabgrass appears. When soil temperatures are 55-70 degrees, crabgrass seeds will germinate and start to sprout. Once these grassy weeds take hold, they can be difficult to get rid of without affecting your grass since they mix into the lawn. 

The soil temperature is the important metric to focus on when applying Prodiamine, since pre-emergent herbicides interrupt the germination process, which is triggered by certain weather conditions. In early spring, apply it when soil temperatures are about 50 degrees, and in the early fall, when they are about 75 degrees. This makes sure the herbicide is in the ground and is present to control growth once the transitional season begins. 

How Do You Apply Prodiamine?

Herbicides like Prodiamine will come with instructions on the product label on how much to use and how to apply it. The product to water ratio will depend on the size of your yard and the strength of an application that you plan to apply. The label should have directions on how much to use for either an acre or an area of 1,000 square feet. The amount is normally measured by dry grams per gallon of water. An online Prodiamine calculator can help you be sure your calculations are correct.

Yard Mastery Prodiamine 65 WDG Professional Pre Emergent Weed Killer Herbicide for Crabgrass, POA Annua and Other Problem Weeds - 5oz Bottle - Water Dispersible Granule

Using a backpack or hand sprayer, the mixture should be applied evenly across the yard. While applying the herbicide, wear gloves, long sleeves, and long pants because the solution can irritate skin. You should avoid putting herbicide out on dry, windy days, or on summer days when the liquid can quickly evaporate. It’s best to do an application in the mid-morning or early evening, avoiding the hottest times of the day.

Be sure your pace is even and that you don’t overapply the product. A lighter application is best if you’re uncertain about the dosage. A split application is a strategy some people use when applying Prodiamine, putting a half-strength solution down in early spring, then another 2 months later in mid-spring.

Since seeds germinate at an uneven rate across the several months over each cool season, the two-pass application spaces a couple of months apart allowing you to apply a refreshment halfway through the season to ensure the summer or winter will be weed-free. A full strength application should last several months and protect you for the whole season.

Does Prodiamine Need To Be Watered In?

Prodiamine needs to be watered in with about half an inch of water after application to create the subsurface chemical barrier that prevents seeds from sprouting. If you use too much water, it can drain the herbicide too deeply below the upper topsoil layer where seeds germinate. If the barrier is too diluted, the herbicide may not be effective.

Watering Lawn

Avoid applying Prodiamine on the same day that it’s going to rain so you can control how much water the ground receives, and if possible, apply it when there are several days without rain ahead.

Can You Over-Apply Prodiamine?

Prodiamine can harm your existing grass if overapplied. The herbicide works by inhibiting root growth in germinating seeds, but the proper application rate won’t harm your mature grass roots. Too much, however, can interfere with the grass’ root growth, or burn and damage the root system. When in doubt, less is more, and a smaller dosage can be followed up 2 or 3 months later with another light pass. 

How Long After Prodiamine Can I Seed?

It’s recommended to wait until the next seeding season to sow grass seed after an application of Prodiamine. If you apply in early spring, you should wait until the fall to overseed. If you put down seed in the same season as Prodiamine 65 WDG, the barrier it creates for weed seeds will affect the grass seed as well.

The application will help your existing grass grow in thick since it won’t have competition from weeds. So, even though you can’t overseed at the same time, you’ll still be encouraging dense grass growth. 

What If Prodiamine Is Applied Too Late?


If you miss the 50-degree soil temperature that is the best time to get in before the crabgrass starts to germinate, there may still be time to get in an application. Crabgrass and cool season annual weeds can sprout and emerge while soil temperatures are between 55 and 70, which lasts for several weeks. Starting late in the transitional season might not catch all the weeds, but it can still prevent some from showing up. 

Do You Need To Mow Or Dethatch Before Applying Prodiamine?

It doesn’t hurt to mow or dethatch the lawn before applying Prodiamine 65 WDG or other pre-emergent herbicides. Clearing the turf of debris and buildup can help the herbicide reach the soil surface more directly, although the watering session immediately following your Prodiamine application will rinse the herbicide off of the grass and thatch, and down into the ground.