Knowledgebase

Crabgrass Prevention #745820

Asked April 23, 2021, 9:49 AM EDT

I have 2 questions. 1.) It's April 23, 2021. Is it time yet to apply crabgrass preventer? I live in Coon Rapids, MN. 2.) I have an unopened bag of crabgrass preventer left over from last spring. It has been kept in the garage since then. It has not gotten wet, but the garage is not heated or insulated. Is this crabgrass preventer still OK to use, or do I need to purchase new? Thanks for your help.

Anoka County Minnesota

Expert Response

It is time to apply the crabgrass preventer. Check the bag for an expiration date or phone/email the contact on the bag.  

It is unlikely to be harmful but may not be full strength.  Without knowing the exact contents, I can’t say for sure.

Mary, Master Gardener, Tree Care Advisor Replied April 23, 2021, 9:56 AM EDT
Mary,

Thanks for the quick response! I really appreciate it!
Also, if I could also ask, is the reason it's time to put the preventer down now because of the warm weather we had earlier on this year? If we hadn't had those real warm days in early April, would the application time be later?

Thanks again.
Kevin



On Fri, Apr 23, 2021 at 8:56 AM Ask Extension <<personal data hidden>> wrote:
The Question Asker Replied April 23, 2021, 10:10 AM EDT

Crabgrass reproduces by seeds. The reason is that the chemicals only work to prevent crabgrass seeds from germinating. Once you see crabgrass it will have no effect on the plants that are already up.  Because crabgrass needs warm soil (55 degrees for 4-5 days) to germinate, it comes up later than most grasses which gives a good window to use chemical prevention.  See the following website for a more detailed explanation.

https://ag.umass.edu/sites/ag.umass.edu/files/fact-sheets/pdf/biology_mgt_crabgrass.pdf

Mary, Master Gardener, Tree Care Advisor Replied April 23, 2021, 10:44 AM EDT

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