Brady from MN

Q: Chris, I live in central MN and plan on using your aerating and over-seeding advise to eliminate my crabgrass on my 1 year old lawn this Fall. I believe Kentucky Bluegrass can take 4-8 weeks to germinate so I would like to give the seed time to germinate before it gets too cold. I also plan to use a pre-emergent next Spring which from what I understand prevents all seeds from germinating. When do you suggest I do this?

My yard is also on hard clay soil, so I would like to aerate soon. When I use my irrigation system I can watch the water flow down the ditch. Can I aerate now and also September or when do suggest I start?

-Brady

A: Hi Brady. Let me address each of your points.

First, most newer varieties of Kentucky Bluegrass really only take about 2 - 3 weeks to germinate provided they are getting regular water. By "germinate", I'm talking about the seed sprouting new green growth, not necessarily filling in to the level of a nice lawn. That will take several more weeks, bringing you to the 6-8 week time frame you mentioned.

One aeration this Fall should be sufficient, and I would recommend that you do it in Early September, BUT.....I need to add one more piece of advice regarding the hardpan clay. Clay is clay is clay. Aerating it is nice, but it doesn't change the fact that clay is clay, and will retain the hard characteristics it has now, just with holes. You need to amend it to start improving soil conditions.

Something that has worked very well for me is spreading well decomposed compost over the lawn after aerating. This infusion of organic matter is like putting in billions of tiny little springs that keep the clay particles further apart from each other, thereby allowing water to drain and air to permeate. Plan on doing this EVERY year until you star to see a noticeable improvement in the lawn. Just aerate first, then spread a 1/4 - 1/2 inch layer of compost down all over. Finally, take a leaf rake and rough up the lawn, encouraging the compost to fill the aerator holes.

Keep in touch and let me know how it works out!