When Should Crabgrass Preventer Be Applied?

We often get asked by homeowners, “When is the best time to put down crabgrass pre-emergents?”

This pesky lawn weed usually appears in the Northeast around late May so the best time to apply a preventer is in the beginning of spring. However, there’s more to it than just putting an “X” on the calendar for treatment. Although timing is important in managing this weed, we also have to be more specific about when and how to apply a crabgrass preventer.

When The Soil Temperature Is Right

Crabgrass doesn’t care about some arbitrary date we put on a calendar. The reality is that crabgrass germinates according to soil temperatures. Crabgrass starts to germinate when the average daily soil temperatures exceed 57 to 64 degrees Fahrenheit. Don’t get this confused with the air temperature, which is one of the most common mistakes most homeowners make when putting down a pre-emergent.

So, once the soil is in this temperature range, the next two weeks will be the perfect opportunity to put down a crabgrass preventer.

Before Or After It Rains?

It’s best to apply a pre-emergent crabgrass treatment right before it rains. This will wash the crabgrass preventer into the soil, coating the crabgrass seeds which will prevent them from germinating and developing roots.

If there’s no forecasted rain, crabgrass pre-emergent can be applied and the lawn should be watered about 2 to 3 days later to flush the herbicide into the soil.

How Long Do Pre-Emergents Last?

There are two different types of pre-emergents: Short Residual and long-term residual pre-emergents.

Short Residual Pre-Emergents:

These are usually effective for around 60 days after application. While the best time to apply crabgrass preventers with short-term effectiveness can vary depending on the weather pattern, the overall best time to apply crabgrass preventers with short-term effectiveness should be about mid-April.

Long-Term Residual Pre-Emergents:

If you don’t know how to schedule the application of a grass weed preventer, We consider opting for long-term options. A single application of these herbicides will eliminate crabgrass from your lawn for the whole season. You can also go with one of our packaged plans which will cover all scheduled treatments for your lawn.

How Often Should Crabgrass Preventer Be Applied?

Since most weed prevention herbicides have a 6-month lifespan, it is strongly recommended that they are applied twice a year.

Leave at least 2 to 6 months between applications, and avoid applying to freshly seeded lawns. Any pre-emergents can cause slow or weak germination of grass seed.