20 Dec When to Apply Crabgrass Pre-Emergent in Minnesota
Crabgrass pre-emergent herbicides are designed to prevent the seeds of many types of weedy grasses from germinating. The first or second application of fertilizer put down in the spring should contain this pre-emergent. There are several brand names of pre-emergent herbicides that are commonly used as an additive to your spring fertilizers. The Dimension brand is known to be among the most effective in the industry and is what we use and recommend.
Apply crabgrass pre-emergent in early to mid-May if possible
Although it is tempting to apply your first fertilizer application shortly after the snow melts in April, this is often too early and the pre-emergent will not last long enough to be effective late into May and June when it is needed most. If you applied a winterization fertilizer treatment the previous fall, that fertilizer has been stored in the roots and crown of your grass and will be used to jump start healthy growth in the spring, which is another good reason why you can postpone your first spring treatment.
However, if you just can’t wait and you do apply your pre-emergent with fertilizer treatment in April, plan on using the same fertilizer blend again in June to prolong the pre-emergent herbicide’s effectiveness. This is a common practice among turf professionals, especially when we receive heavy rains in the spring or when a lawn is heavily irrigated.
You can apply the pre-emergent with fertilizer mix again in place of the recommended June/July straight fertilizer treatment. Dimension is thought to last about 10-12 weeks effectively in the soil. However, if we get a lot of rain in April and May, which we oftentimes do, I would only count on about 6-8 weeks of effectiveness from your pre-emergent. With that being said, make sure to wait until soil temperatures are in the high 40s to low 50s to apply your pre-emergent application.
A good indicator that can help tell you when the time is right is to wait until the lilacs bloom.
Crabgrass will germinate when soil temperatures reach 55 degrees Fahrenheit for a consecutive 48-hour period, so make sure you have your pre-emergent freshly applied before your soil reaches 55 degrees.
Dimension, unlike many other pre-emergent herbicides, has some post-emergent qualities as well. It will kill small seedlings up to about 4 weeks old and up to the 2-3 tiller stage. So even if you think you’re a little too late to apply, making this application can still be very effective within the first couple weeks from the time you first start to see crabgrass emerging.
You might want to learn about turfgrass issues, and we have loads of other content on our blog. Learn more about common turfgrass diseases and how to prevent them. You can also read about methods to prevent weeds in turfgrass that don’t involve pre-emergent.
If you’re interested in getting a fertilizer and weed control package developed by our U of M Turfgrass specialists, let us know. Learn what our fertilizer and weed control services can do for you by requesting a quote or calling (763) 568-7251 today!