In the spring I dug up lawn, took away the old grass, and spread loam/compost. I seeded with mixture of rye and fescue - expensive seed. Unfortunately, on one side, I have close to 70% crabgrass, and on other side 20% crabgrass. After reading this forum, I was planning to overseed and I have read that the crabgrass will die on it's own. I am in the Northeast. When is best time to overseed? What is best way to overseed: new loam and seed only, or dig up existing lawn, or rake existing? Should I use same mixture or add Kentucky Bluegrass? I'm wondering if there is any grass mixture that is strong enough to block the weeds. I have been mowing each week and I have been fertilizing to make existing grass stronger.