Hi I’m trying to understand what may cause this issue with my lawn. I put down new top soil and reseeded my lawn about a month ago. Initially the grass grew out well but after a week or so I started noticing patches. Initially I thought it was grubs, but when I inspected the grass, the roots were still intact. Then I noticed the brown areas of the grass were very mushy. The patches started to spread and my once green lawn (for about 2 weeks) is now patchy brown. I’ve attached some photos before and now. Appreciate any insights or advice. Thanks
Welcome to Master Gardeners of Toronto.
The picture you provided looks like the grass is rotting. We have had a lot of rain lately and some of it was rather torrential which isn’t particularly kind to new roots.
By any chance when you put down the top soil did you:
1) mix it in well with the existing soil to a depth of at least 10 to 15 cm (about 4 to 6 inches deep)
2) bank the soil slightly to ensure adequate run off and prevent pooling
You didn’t mention where you are but most of the terrain around Toronto is clay or mixed clay which is quite compact in residential areas. You already said the lawn was “very mushy”, so this is could be part of the problem.
Please visit Landscape Ontario’s guide to growing a lawn from seed which can be found here.
To save you a little time, here is a direct quote from the above article:
“The area to be seeded should be as level as possible, with a gentle slope away from buildings. If possible, avoid steep slopes or terraces where water may erode or wash away topsoil. The entire surface should have a layer of good topsoil about 12 to 15 cm deep. It may be advisable to mix peat moss or composted manure into your topsoil for best results.”
Be advised that weakened grass may now have other issues such as mould, fungus and pests but based on your description and the picture provided the root issue (bad pun) might have been the original installation.
Landscape Ontario also has a resource to provide you with trusted professionals who can do a site inspection and confirm these findings and any other possible issues.
Find a professional near you here