I moved into a new subdivision where the yards were, of course, very hard clay (no top soil remained after the construction). I brought in top soil when I installed my sod lawn, which now looks great. A neighbor said that someone told him it was not necessary to put down top soil; that the sod can be placed right on top of the clay. Is that correct?

The overall health of your lawn is a direct result of proper soil preparation prior to the installation of the sod. The effort you put forth now determines the quality of your lawn for years to come. It also makes a difference in the routine maintenance that you will have in the future. It is very difficult to improve the soil at the root level once the lawn has been established. Sod that is laid over a thin layer of topsoil or compacted subsoil produces disappointing results due to poor rooting and development. It is a good idea to have a soil test done by your county MSU Extension to determine the pH and amendments that are needed. The following steps are recommended for sod installation:

1. The existing soil should be tilled thoroughly.
2. Add organic material if the soil is very heavy or sandy.
3. Topsoil that has been added should be well mixed with the subsoil to a depth of about 6 inches.
4. Apply recommended soil amendments and fertilizers at this time. In general, a pre-plant fertilizer can be spread over the entire area at a rate of 1 pound per 100 square feet.
5. Rake the area smooth, filling in the low spots and removing larger clumps.
6. A finish grade should be made using a steel garden rake, making sure that there is a way for water to run off away from the house.
7. After laying the sod, roll it with a water roller to remove air pockets.
8. Water, water, water. The sod should be kept constantly moist and should be watered 2 or 3 times a day for 10 days with heavy foot traffic avoided for the first two weeks. And then, let the mowing begin!

I have an invasion of wild violets in my lawn. What should I do to get rid of them?

I hate to be the bearer of bad news, but once violets have established a foothold in your lawn, they are extremely difficult to get rid of. Unfortunately, we have no good selective herbicide for violets. The trimec sprays may temporarily slow them down, but they usually bounce right back. Try using Roundup, a nonselective product. If the violets are just getting started, spraying small areas of the lawn and reseeding those areas after the kill is complete is an option. Another option is to paint the Roundup solution on the violets, avoiding the grass as much as possible. Since Roundup is absorbed through the leaves (not the roots), this is an effective approach that does little harm to the grass. On the other hand, if the violets have invaded a larger area of your lawn, you have to make a decision: 1) kill both the grass and violets and start over, 2) if you are very patient, paint every violet leaf in sight, or 3) learn to live with the violets (the flowers can be quite attractive!). The third option may work for naturalists, but lawn purists would be appalled!

Since it is difficult, if not impossible, to hold these violets captive, do not plant them in the first place unless their spread is your goal. If they do escape to your lawn, the earlier you attempt to bring them under control, the more successful you will be in getting rid of them.