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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.

What plants will grow well under pine trees?  The space is quite shady and has pine needles pretty much covering it. The soil is fairly dry.

Although it can be challenging, it’s a myth that nothing will grow under large pine or spruce trees. The reason many plants don’t thrive under evergreens is dense shade and extreme dryness. The trees have dense root systems and are strong competitors for soil nutrients and moisture.

The cure: If you plant perennials where they face dry shade conditions, give your shade garden plants the best possible chance by watering deeply and fertilizing more often than you normally would, and put a layer of mulch down. To let more light into your shade garden, consider elevating trees by cutting off some of the bottom branches. This works with deciduous trees, pine trees or thin older spruces, but don’t do this if your evergreen is a perfect Christmas tree shape with branches down to ground level. In that case, I would just mulch under the tree rather than disfigure it. The following is a list of some “survivor perennials” for dry shade you might want to try:

• Barren strawberry (Waldsteinia): A low-growing, dense mat of leaves that slightly resemble those of strawberries.

• Big-root geranium (Geranium macrorrhizum): Attractive and aromatic leaves, flowers in late spring in colors ranging from white to pink and magenta, depending on cultivar. Not to be confused with the common annual geraniums of the genus Pelargonium.

• Barrenwort (Epimedium x versicolor): Attractive heart-shaped leaves. With its delicate yellow flowers, ‘Sulphureum’ is the most popular cultivar.

• Dead nettle (Lamium maculatum): Look for cultivars such as ‘Beacon Silver’ with rosy pink flowers and silver leaves edged in green or the white-blooming ‘White Nancy.’

• Heart-leaved bergenia (Bergenia cordifolia): Large, leathery leaves and rose-pink flowers in early spring. Looks great in a big grouping.

• Sweet woodruff (Galium odoratum): Finely textured leaves and white flowers in spring. This is a top-flight groundcover in the dry shade garden. Note that it can be invasive.

• Groundcover plants: To make it really easy, consider the big three ground covers: ivy, pachysandra, and periwinkle, which are all tough evergreen perennial plants, perfect for the shade garden.

I have several plantings of the narrow arborvitae ‘Emerald.’ During this past winter and especially with the late spring snow fall, they have become bent over about midway up, even though we shook off the snow-laden branches. Is there anything I can do now to help them return to their straight, upright growth habit?

Due to their multi-stemmed nature, arborvitae and junipers are especially susceptible to having their limbs distorted from heavy snow loads. These loads cause the branches to bend and separate from the center of the plant. If the snow load is heavy enough, the branch can break.

Snow should be removed as soon as the storm stops by either using a broom to jostle the branches, gently shaking the tree so as not to damage the bark or by sweeping upwards. In case the weight of the snow has severely bent an individual branch, try re-positioning it by tying it to other branches within the shrub.

In more severe cases, like with yours, you can attempt to straighten them by tying a soft rope (their bark is thin), even old panty hose or stockings will do, around the trunk. You will need to tie above and below where it’s bent. Attach a rope to that and pull the tree straight. You will have to anchor the rope and leave it on for at least 6 months if they have been bent for a while. There is no guarantee that they will straighten, but it’s worth a try.

Evergreens can be protected from snow breakage by tying the branches together with strong rope or twine before winter snows are expected, but after the first severe frost. Fasten it near the tip of the tallest branch and then spiral down around the entire tree and tie it off to the base. You do have to remove it at the first sign of spring.

I have a clematis on an obelisk and all the leaves are brown. Do I remove those and cut down the clematis? If so, how much should I leave, or should it be cut back to 4 inches above ground?

A clematis can look quite brown and dead after a long winter. It is tempting to cut it back to the base, along with other perennials that benefit from this tidying up. However, the clematis is the poor man’s pruning minefield. The key is knowing when your clematis blooms, for that determines the “when,” the “what,” and “how much” to prune. Spring-flowering clematis (April-May) flower on their old wood (previous season’s growth). Pruning before flowering removes their blooms. Once flowering is finished, old stems can be cut back in early summer, enabling new growth to ripen the rest of the season for next spring. Clematis alpina, Clematis macropetala and Clematis montana fall into this first category.

The second clematis group flower on short stems produced on last season’s old wood. These are the early large-flowered hybrids, the double and semi-double flowers, and the mid-season hybrids which flower by the end of June. Pruning is essentially light. Remove dead, broken or weakened stems. Watch out you don’t remove a vine at the plant base that has flowering buds higher up. Varieties in this group are ‘Miss Bateman,’ the well-known ‘Nelly Moser,’ ‘Duchess of Edinburgh,’ and ‘General Sikorski.’

The third clematis group only flower late in the season, well after mid-June and into autumn. They only flower on new wood. Pruning involves cutting back all the previous year’s growth to just above a good pair of buds, about 10 to 12 inches above ground. Don’t prune this type of clematis any earlier than the end of February or beginning of March. Hybrids in this category are ‘Jackmanii,’ and the Clematis viticella cultivars.

Knowing when your clematis blooms is the key to making an informed pruning plan.

What effect will the late April, heavy snowfall have on bulbs, perennials, shrubs and trees this season? Is there anything I should be looking for or doing this summer because of it?

Actually the snowfall was like a slow-release watering for most of the plants in question. Some of the more delicate bulb blossoms succumbed more quickly and we didn’t get to enjoy their wonderful flowers as long. Perennials were just starting to emerge and welcomed the slow drink of water. The melting snow was a far better source of early season moisture than several downpours. Heavy rainfall can quickly flood and set new root growth to rotting because the soil hasn’t had the chance to warm up and process that much water. The ground is still waking up too!

The downside for shrubs and trees is the wet snow sticks and applies a lot of weight to branch structure. Any broken tree limbs or shrub branches should be properly pruned out and removed. Shrubs may need to be reshaped for aesthetics or replaced if snow broke out the center crown. Be on the lookout for insects or funguses that might home in on the pruning cuts this early in the season. Make sure injured trees and shrubs get plenty of consistent water and air circulation to help their healing process. Sometimes a young tree sapling, like a maple or pine, may lose a central leader. It is important to train and shape a secondary leader branch to become the central upright to maintain the natural configuration and strength of the tree.  Otherwise you have a tree that grows with a flat top, becomes top heavy as secondary branches fight for dominance, and becomes a candidate for further storm damage.