Answer: Grass seed needs to be planted early so it has time to grow before the heat of summer hits. The best time of year to plant grass seed is actually late summer to early fall when it has cooler growing weather during fall and the following spring to become established before the stress of summer sets in. But, you could seed now and the grass will germinate when the soil warms up a little.
Crabgrass preventer needs to be put down very early before the crabgrass seed begins to germinate, the rule of thumb is when the forsythia bloom. However, the preemergent crabgrass preventer will also stop your desired grass seed from growing so you can't really do both at the same time. You could try raking out the crabgrass and seeding the bare patches. (Crabgrass is an annual grass and is crowded out by a healthy lawn.) Or, you could spot treat the growing crabgrass with an herbicide containing glyphosate and then reseed. Be careful to read and follow all of the label directions for the herbicide.
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