Crab grass preventer
When is it time to apply this preventer?
Hennepin County Minnesota
Usually at the end of April, but this year may be earlier. There are two good indicators of when to put down pre-emergent. One is soil temperature. Use an inexpensive soil thermometer and put down the preventer when the soil temperature one to two inches down is 55 degrees over several days:
Second is to use what's in bloom around you. Put down the pre-emergent when the forsythia is in full bloom: