When is the best time to apply crabgrass control products and what is the best product (chemical) to use? I have read many answers to this question which apply in most cases to a broad area or an area other than Minnesota. We just moved here from Indiana and our yard needs a major over haul because of the weed problems that we have and want to start with the crabgrass. Do you recommend one application in the spring or multiple applications during the summer months.
Freeborn County Minnesota
Thank you for the question. Crabgrass is an annual warm season grass. This means that the plant dies each year but the seed it spread last year is just waiting for the soil to warm up to sprout. Control is best achieved by preventing the sprouted seed from emerging from the soil which is what pre-emergent herbicides do. Pre-emergent herbicides for crabgrass should be applied before soil temperatures are 55 degrees in the upper 1-2 inches for several days. You can find data on soil temperatures near your area by reading this recent article by Sam Bauer, University of Minnesota Extension turf grass specialist: http://blog-yard-garden-news.extension.umn.edu/2016/04/spring-preemergent-applications-for.html. Try http://www.gddtracker.net/, put in the zip code for your County (56032 is the one we tried) and click on the link to the right named Crabgrass PRE. The graphic shows that now is an optimum time to use a pre-emergent for crabgrass in your area.
There are some studies that show that split applications of herbicide can be more effective than a single application. You might choose to divide the amount recommended in half and apply half now and the other half in early June. Depending on what you plan to do this year to renovate your lawn, this may not be a good idea because most pre emergent herbicides will also prevent desirable plants such as grass seedlings from emerging. If you plan to overseed, there is really only one pre-emergent product that won't harm the new seedlings: Tupersan or sideron. Be sure to read label directions and follow exactly.
A lawn renovation approach to consider is to get control of the weeds, correct the situation that favored weeds over grass and overseed mid August to mid September. This is the time when competition from weeds is minimized and the new grass can get a head start.
You might find our lawn care information useful: http://www.extension.umn.edu/garden/turfgrass/
Good luck and thank you for contacting Extension