In order to prevent crabgrass, you should first know how its life cycle works. The life cycle of the crabgrass plant begins when the soil temperature reaches 55°F for four or five consecutive days and the seeds start to germinate.
Crabgrass seeds often germinate from early spring to late summer. They grow all the way until the end of the growing season until they are killed off by fall frost, and leave behind seeds to germinate and begin this process all over again in the spring. Crabgrass can be particularly hard to control, as a single plant is capable of producing 150,000 seeds.
If you want to seed in the spring you should:
Seed as early as possible, then wait three mowings after seeding to put down an application of Crabgrass Preventer plus Green-Up Lawn Fertilizer. If you apply seed early and it doesn’t start to germinate for several weeks, applying crabgrass preventer too early will kill it. Make sure to apply it to a dry lawn in late February to mid-May.
Crabgrass preventers can kill new grass seeds before they begin to sprout. Only apply a pre-emergent when seeding if it is specifically formulated to be safe to use with new seedlings.
Applying crabgrass preventer in the late spring, and then seeding your lawn in the fall as this is when soil temperatures are ideal for germination and there is less competition from weeds.
Whichever you decide, the best way to prevent crabgrass from becoming a problem is to prevent the seeds from germinating in the first place.