We spread crabgrass preventer with fertilizer, using about half of the crabgrass preventer needed for the year in the first application. The next application we spray the remaining half. The reason we do this is to try to get better control on the crabgrass.
Crabgrass preventer is a pre-emergent chemical that stops the crabgrass seed from germinating. That is one reason we try to get it on quite early in the spring. On the sunny south side of brick houses or on a south facing hillside, the soil temperature can be much warmer than the rest of your lawn. Especially so with all the 60 to 70 degree days we can get.
The way crabgrass preventer works is, it only takes about half the yearly rate to stop the crabgrass seed from germinating. The remaining half that we put on stays in the soil and keeps all the seeds that would germinate throughout the year from germinating.
So we do the split application in case we leave any skippers — we are less likely to skip the same area twice. It gives us about 6 weeks longer control by doing half now and half with the second application.
This application also keeps good grass seed from germinating, so that is why it is difficult and not recommended to do spring overseeding. If you have an area that you would like overseeded, let us know before we spread this first application.