I have been getting this question a lot in the past week, and the answer is….it depends.
Aeration and overseeding should be performed during the growing season of the type of grass that is on your lawn. In St. Louis the growing season for fescue and bluegrass is the spring and fall. The growing season for zoysia is summer.
First lets talk about what happens in the spring lawn growing season. Springtime is when your grass starts to come out of dormancy and begins to grow. Lawns start to green up and begin to look good. Now grass is not the only plant that begins growing in the springtime in St. Louis. Crabgrass begins to germinate in lawns as well. The crabgrass grows from seeds left in the soil from last season. Crabgrass dies in the cold weather and it leaves hundreds, if not thousands of seeds behind. These seeds sit and wait for the warm weather to come back.
Ok so know that we know that spring is a growing season for grass and crabgrass, how do we prevent the unwanted crabgrass from germinating?
Put down a pre-emergent plus fertilizer in the spring. The pre-emergent herbicide prevents seed from germinating in your lawn, including the unwanted crabgrass. The fertilizer will add nutrients to feed the existing grass. The pre-emergent does not harm established grass, it needs to be put down before the crabgrass starts to grow.
So, since the pre-emergent prevents all grassy seeds from germinating it will be pointless to plant new grass seed at the same time. This is why it is ideal to plant new seed in the fall. The fall will allow the new seed to grow and the winter will kill the unwanted crabgrass, and you will be able to put down a pre-emergent herbicide on your already established grass in the spring.
I know this is probably confusing to read. If you have any questions do not hesitate to call any of the professionals at St. Louis Lawn Care, Inc. We will happily answer any questions you may have about your lawn