The Q&A Archives: Re-seeding a lawn

Question: Due to a severe case of crabgrass, I decided to kill off my small lawn and start from scratch. I roto tilled my lawn, then over several weeks, I applied Triple Strike several times removing more and more weeds. Once everything was dead, I spread a layer of sifted good quality top soil. Heavy rains prevented me from spreading seed for several weeks so I had to lay another layer of sifted top soil since my ground had hardened. I bought the second layer of top soil from a different lawn and garden center. I raked in the soil, spread good quality Scotts grass seed and raked in into the soil. I applied green mulch, which was recommended by the garden center. A week later I applied Scotts Starter with Haults. I watered my lawn faithfully twice a day. Within a few days I had beautiful grass emerging but also had a lot of crab grass and various weeds popping up. I now have more crabgrass then I did before I started this project and I now have weeds growing that I never had before. After all the time, energy and expense I put into this, I don't want to just give up and let the crabgrass and weeds win, but I hate to have to start all over again and go to the expense and labor of killing everything off; roto tilling; and laying new top soil. I've contacted the garden center that sold me the bad top soil, but they are unwilling to do anything to help me remedy the situation or to compensate me. Should I kill everything off again to kill the weeds and crabgrass? I don't mind re-applying grass seed since that was the easiest and least expensive part of the entire process, but do I really need to roto till again (the ground is a bit hard now)? And do I need to lay more top soil (the good quality stuff that I got from the first garden center)? Would running an aerator work better? Any advise would be greatly appreciated.

Answer: Based on your description it sounds like you are trying to do things right. Keep in mind that summer is just not the best time to plant a lawn -- but early September is perfect. There are many factors involved in starting a lawn. And any time there is bare soil, nature will try to cover it (with weeds) and weed seeds can be blown in. Every time you till or disturb the soil, more weed seeds are brought to the surface where they can germinate. And yes, they can be imported with top soil as well. And, top soil is not a regulated product so you have no real way of knowing what the soil is composed of.

I am concerned that the soil has turned hard; ideally your soil should have ample organic matter in it to prevent that. Correct watering should also help keep the soil from turning hard and compacted.... The basis of a healthy lawn is good soil conditions. Since you have a little time, I would suggest you work with your local county extension to run some basic soil tests and begin with preparing the soil based on the test results. You may simply need to adjust the pH or fertility, or it may require additions of compost. Since you have already fertilized you may not need to do that again. The only way to know is by testing, then you can work with them to develop a plan.

Crabgrass is an annual weed, so it may be that your perennial grasses will crowd it out. The desirable grasses may also crowd out some of the other weeds you are seeing -- if you can keep conditions ideal for the grass and have planted a grass variety suited to your local conditions and soil. Spot treatment is also an option, to try to preserve the good grass and remove the most invasive weeds while they are small and before they have gone to seed or spread.

I would not recommend aerating a newly seeded lawn. A spike style aerator is not helpful in any case. But aeration might be something to do next August/September if you use a core aerator and pull out plugs of soil, then rake them off and replace the material with compost or something like that. Instead, this year you might be able to overseed in early September with a slit seeder if the stand is really sparse. That way you will not be starting from scratch and can preserve the grass that you already have.

Again though, this is something to work out by consulting with your county extension -- they should be able to help you do some turf analysis and identify the weeds and help you plan how best to approach the problem.

Best of luck with your lawn!

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