Crabgrass is a warm season annual weed that germinates, lives and dies all in the same year. Though crabgrass doesn’t end with growing season. While they live, each crabgrass plant produces 150,000 seeds. These seeds stay behind and are ready to germinate the following spring and starts the cycle all over again. Seeds that don’t germinate right away can remain viable and stay around to germinate into future years.
Effective control requires preventing crabgrass seeds from ever becoming seed-producing plants. With hundreds of thousands of crabgrass seeds potentially waiting in your lawn preventing their successful germination is essential. Crabgrass preventer products use what are known as “pre-emergent herbicides”, which target germinating seeds before new shoots can emerge from the soil. They work by inhibiting seed germination and root development so that seeds don’t become established plants. Because crabgrass preventers only work before crabgrass seedlings emerge through the soil, timing applications right is critical to success. Preventers must be applied before crabgrass seeds germinate. Crabgrass seeds can germinate from early spring until late summer when soil temperatures are right.
In spring, crabgrass starts germinating when soil temperatures warm to 55 degrees Fahrenheit for 4-5 days in a row. Once soil temperatures warm and germination starts, crabgrass seeds continue germinating until soil temperatures exceed 90 degrees Fahrenheit. Once seeds germinate and crabgrass sprouts emerge, pre-emergent herbicides no longer work. Then its time for post emergent herbicides, which target plants instead of seeds.
When it comes to tough grass like crabgrass its always best to consult a professional that’s familiar with using those types of herbicides to avoid hurting the lawn.