Question
I have some low spots a few inches deep in my lawn, caused by decayed tree roots.  I want to level them with topsoil.  Will the grass grow through the topsoil, or do I need to reseed?  Thanks for sharing your expertise.

Answer
Hi Jack,

All of the 'tufted' cool-climate turf-grasses like Kentucky-Bluegrass, Fescue, and Rye cannot tolerate being buried even a inch or so.  Once their central crown becomes light-starved, they will suffer physiologic shock and die.  So, you will probably have to re-seed these grass-types when raising the grade by adding a layer of new soil.

You may be able to purchase all the top-soil you need for your project from the garden center where they usually sell potting soil and fine top-soils by the bag. They may also sell the seed you need.  I recommend that you use named certified or patented seed and make a note of the cultivars name in case you need to do a 'booster seeding'.  Most cool-climate grasses will need to be re-seeded every fall to keep up a dense stand.  

Try to re-seed before the heat arrives in your area, the seedling grasses may need to be watered several times a day to keep them well hydrated enough to get going good.
Good Luck!
Jim G.