Question
I had a septic system replaced in the spring. The contractor put down 4" of loam and had it hydroseeded. It looks awful. The lawn is thin and some of the grass is already dying.The biggest problem is crabgrass, which is spread fairly evenly over the whole thing. The contractor suggested that we slice seed it in the fall. What do you think? Should I put down a grabgrass killer? I fertilized the lawn 3-4 weeks after it was hydroseeded and have watersd it regularly. I live in Massachusetts. Thanks for your time

Answer
Crabgrass is an annual grassy weed which will die with first frost. Before it dies, it will set seeds which will germinate (sprout) next spring when the soil (no air) temperatures goes above 55F for 5 consequtive days or more. This is typically in early spring in northern part of USA. You cann slit seed the lawn in fall and it will sprout and grow before spring. The fertilizer w/crabgrass preventer (such as Scott's Turfbuilder with Halts) will then act as a barrier which protect the crabgrass seeds from sprouting. This must be put down in early spring to be effective and be watered in. Check with a local garden center for timing. Do not wait until late spring when temperatures have warmed up. Since these fertilizers w/crabgrass preventers also prevents grass seeds from sprouting, planting grass in fall and fighting crabgrass is spring is recommended.

Start grass establishment this fall as soon as the summer highs goes down. Do not wait too late or the soil temperatures becomes too low.