Last summer was tough on lawns in a lot of the country.
Although you can plant grass seed any time, the best time is in the fall – the new plants use their energy forming a deep root system in preparation for winter instead of putting their energy into growing green stuff. Fertilizing works the same way – if you don’t plan to do it throughout the season it’s better to do it in the fall than in the spring.
Since you didn’t seed last fall, you now have to deal with the fact that most pre-emergent crabgrass control will also prevent any new grass seed from sprouting and that you shouldn’t aerate after putting down the crabgrass preventer.
What I would do is aerate and put some seed down early this spring. If you want to fertilize be sure to use something appropriate for spring … less nitrogen than summer fertilizers … you want to promote root growth in spring, while the grass is wanting to send up lots and lots of fresh green sprouts. The idea now is to get the lawn, particularly the roots, healthy and dense to make it harder for the crabgrass to thrive later on.
When the weather gets hot and the crabgrass starts to appear, get a bottle of something like Ortho Weed B Gone Plus Crabgrass Control and spray it as it appears. You’ll pretty quickly learn to spot the crabgrass from a distance by the distinct color. Just walk the lawn once or twice a week and spray the buggers; it won’t die overnight but you will likely find great satisfaction is watching them shrivel over the course of a few days.
And then, if/when the crabgrass really starts to pop up all over the place, look for the hose-end sprayer for the Ortho or whatever brand you’ve chosen (just be sure it mentions crabgrass) and cover the whole lawn. I find the sprayer much more effective than the granular stuff you put down with a spreader. The stuff will likely say not to do more than two applications per season, so spray when you start to see heavy infestation and then again about 10 days or so later. That should get it under control. Continue with spot spraying for any stragglers.
If you think you don’t want to do all the chemical treatment and would prefer to dig them out, keep in mind that if you miss half an inch of the root you have only delayed the plant, not killed it. And the spray will also whack out your dandelions and most other weeds, too.
Then in the fall aerate and overseed again. Exactly when depends on where you live; in the northeast, around Labor Day is right – and then next spring, put down the pre-emergent about the time the forsythias are dropping their flowers.
Bingo, the two year plan for crabgrass control. Your kids will love the lawn.