Gardening Q&A with Richard Nunnally

Q:My lilac is leaning helplessly. It is at least 20 years old and has been blooming nicely. Two or three years ago, it started leaning. I tried to tie it to a stake; but it keeps leaning a little more as time goes by. I now have a heavy wire pulling it toward a steel stake. Is it losing its roots? Will it ever do any better? Should I cut it way back?

Answer: The lilac in the photo you attached is leaning to reach the sunlight. It looks like the shade trees behind it have grown and are blocking out the light it needs. As you know, lilacs need full sun. Many plants will grow toward the light in order to be able to produce food for their roots. Cutting it back is about the only way to get it to straighten up again. However, that would only be a temporary fix as long as the shade trees are blocking out the sunlight from one side. It will grow upright for a while but will soon start leaning toward the sun again. The good news is it seems to be blooming nicely, even though it's leaning.

Q:In mid-September, I found bright red and purple caterpillars with two broken line stripes on their backs eating my azaleas. They are bristly and about an inch long. Is there anything I can do to prevent them from coming back next year?

Answer: That critter is called the red-headed azalea caterpillar. It eats a lot of leaves quickly. Then they disappear as quickly as they came. The good news is the plant will be fine. In fact, it will probably make new leaves immediately. There really isn't anything you can do now to prevent their return. Fortunately, they may not be back for several years. If they do return, treat them as soon as you see them.

Q:Who can I call to eradicate bagworms that are damaging our 30-foot tall row of arborvitae?

Answer: Most any good arborist can treat arborvitae for you. However, the best time to treat them is in late May when the young larvae are just starting to feed. There are several good insecticides available that are systemic and can be applied to the base of the plant, rather than used as a cover spray. This way you affect only insects that are actually feeding on these trees.

Q:A family member has a backyard full of tree roots from a neighbor's tree. The tree is just on the other side of their common fence. She would like to cover these roots with dirt. Then she wants to plant a ground cover to grow over top of the large roots. Can you suggest any good ground covers and do you think this will work?

Answer: I'm not sure a load of dirt is the answer. Trees that have surface roots will always have them. If she covers them with soil now, in a year or so the roots will have grown back to the surface, and she'll be back where she started. I do like the idea of putting a layer of mulch over the roots and then planting a ground cover like periwinkle. This ground cover will not climb the tree but will spread and run over top of the roots.

Q:We planted flowers on the alley side of our house, but the city said we had to cut it all down to the ground, which we did. This included daylilies, hydrangeas, roses, rudbeckia, and daffodils. I think the daffodils will survive. However, if we dig everything else up and replant them, will they grow back next year even though we had to cut the foliage before it died back?

Answer: How unfortunate that you had to cut down all those wonderful plants. You're right, the daffodils should do fine. Also, the rudbeckia and daylilies should do fine. The hydrangea should recover but probably won't bloom for a couple of seasons. The roses would be my only concern. If you cut them to the ground, you may have cut them below their graft. If so, the rose that returns from the root stock, probably won't be like the one you had before. If you left the graft above ground, it might have a chance.

Richard Nunnally is a freelance writer and host of WCVE's monthly gardening show, "Virginia Home Grown." He can be contacted at .