It’s mid-March, the clocks have sprung forward and sunset is well after 7:30PM now. I am already taking advantage of the additional yard time after work, getting some much needed pruning done.
The days are longer too, almost up to a full 12 hours of day length! The more sunlight available means the more your grass can grab it for photosynthesis. That’s a trigger for it to wake up and start growing.
Longer days also mean the soil is heating up and that is what drives our strategy for pre-emergents to stop crab grass. Soil temperatures tell us when to apply prodiamine.
If you have not already, go download my free pre-emergent guide that will give you details on the strategy overall.
Soil Temperature Milestones
We do prodiamine “split applications” in my strategies. Split applications mean we apply 2 “lighter” applications of prodiamine in spring rather than 1 “heavy” treatment. I prefer the split applications strategy because it gives you a hedge against unforeseen circumstances that could lessen the effectiveness of your application.
The first application goes down as soil temperatures cross 50F heading to 55F and the second one goes down as they rise past 65F heading to 70F. Once soil temps pass 80F the window closes and there is no more need to apply.
(Wondering how to track soil temps at your house? Get my FREE app - it’s soil temps in your pocket!)
50F - 55F Soil Temperatures
We can look at a few areas across the country that are sitting in the perfect window to get that first application of prodiamine down. I’m looking at the 5 day average as the marker for the milestone. (this is done for you in my app)
Tulsa and Nashville are perfectly in the window now - time to throw down!
Norfolk and Louisville are right there too - just approaching the perfect time to apply, Thrower Down and hope for the best!
Is It Ok To Be Early?
We had a significant early warm-up in February and soil temps were pretty warm. Many folks applied their prodiamine then - is that ok? The answer is yes! Being early is perfectly fine, especially down here in the south where the ground doesn’t really freeze anyway.
Plus, with my strategy, I have plenty of redundancy built in so if you are early you still have plenty of coverage time.
Am I Late Then?
On the other side of this equation are those of you who may think you’re late. For whatever reason you didn’t get your first application down right as the soil temps were perfect, and you’re wondering “Am I too late then?”
The answer is: you are not too late.
Remember, crabgrass seeds germinate at soil temps between 55F and 80F. That’s a long window of time that lasts all spring. We want to get 2 applications of prodiamine down within that window.
If you’re a little late and prevent 90% of the problem, that certainly is better than preventing none of it. You follow that logic? Being a little late is still doing some good!
The other thing about that is that not all of the crabgrass seeds start growing exactly at the same time on the same day. Some seeds may be buried 3” down in the soil profile, others may be 6” down, so the temps hit one sooner than the other.
Some areas in the shade may stay a little cooler vs those in the sun. And then water penetration can be different as well. All of these factors mean that seeds are pretty much at all stages of growth during the spring window.
Soil Temps Crossing 65F heading to 70F
Now let’s look a little further south. Many of us are coming up on our second application of the season already! Seems crazy to most of you I’m sure but let’s look at the data.
Looking at Waco, TX and Montgomery, AL, you folks are right in the window to apply your second application of prodiamine. If you have not applied any prodiamine yet, you should go ahead and get started now. You did miss the first one, but it’s better to prevent crabgrass from now onward while the spring window is still open. Remember, stopping 50% of the crabgrass is better than stopping 0% of it. Throw’er Down!
Who is Too Late for Pre-Emergent?
I’m here in Bradenton, Fl - west coast of Florida just south of Tampa Bay. My soil temps are hovering up over 80F the last several days. I’d say that if you are living here where I do, we are now past the window for prodiamine for the season. No need to apply again until the fall time.
Instead, you are best to start looking at post emergent weed control to control all the weeds that you are probably seeing!
Here is a video I made showing you how to mix and apply store bought weed control.
I’ll see you in the lawn!