When To Apply
Crabgrass Preventer

What If You Miss The Best Time To Apply?

Are you not sure when to apply crabgrass preventer? Conventional wisdom says you must apply pre-emergents prior to, or early in, the growing season. Obviously, the start of crabgrass hunting season will vary, depending on where you live.

The problem always develops that many people do not get it done when the best time arrives. Is that the end of the story? Can you effectively apply pre-emergent at other times?

Would you consider 50% success in preventing crabgrass a victory? Asked another way, would you feel worse about a lawn completely filled with crabgrass, or a lawn only half affected?

The most practical answer to ‘when to apply crabgrass preventer’ might be ‘whenever you have the time, money, and willingness to do it!’ Let’s discuss why that makes sense.

When To Apply Crabgrass Preventer For Early and Best Control

Crabgrass seeds can germinate each year when nighttime soil temperatures reach over 50 degrees for 3 days. This “wakes up” the seed, and starts it on its process of growing up to be your worst nightmare.

Note, the seed “can” germinate at that point. So common thinking is to have the preemergent applied no later than this. That could mean a December application in Southern California, but April in Ohio.

So you can diligently observe soil temperatures, either through your own monitoring, or a local source. Perhaps the newspaper in your area provides such information, or the county agricultural department. State universities may provide this information on a website as a guideline for when to apply crabgrass preventer and other products.

But, how much of the current crabgrass seed lurking in your yard will germinate this early?

The earlier that you apply the preemergent, the sooner it will lose effectiveness. The duration of effective control depends on the type of product, and how heavy of a concentration you apply.

The control could last 2 to 3 months, or longer than 4 months, depending on several factors. So the date chosen as when to apply crabgrass preventer could determine if you need to do it one or two additional times.

Is Early Application The Best Time Or The Only Time?

Crabgrass seed doesn’t line up at the germination window like holiday shoppers do at stores on the morning after Thanksgiving. Some are late sleepers.

Researchers at the University of Maryland determined that the minimum daytime soil temperature to observe the initial emergence of crabgrass was 54 degrees.

The major emergence of crabgrass, however, did not appear until soil temperatures were at least in the range of 60 to 70 degrees.

This explains something that you have probably observed. There seems to be no end to the appearance of new crabgrass throughout the warm months of the year. Individual seed specimens will vary by size, maturity, and depth in the ground, as to when they are ready to germinate.

Soil temperatures will vary throughout your yard. How much is the soil shaded during the day? The thickness and height of your grass can affect this. So can trees, shrubs and buildings nearby, as well as cloudy days. The amount of moisture present, wind, and more, can also affect temperatures.

The end result is, these pesky weeds will pop up consistently over an extremely long growing season. Will the late bloomers be met with preemergent, or will it have worn off already? So there really is not one small window that is fitting for when to apply crabgrass preventer

What if you miss the early date for applying the preemergent? You watch crabgrass sprouting for a month because you don‘t have a chance to get to yard chores. Does that doom you to allowing the remaining seeds to have their way the rest of the growing season? Certainly not!