Green Scene: A gardening Q&A

April 1, 2011

Now that spring has arrived, your questions have more urgency. Noodling time is over, and gardening has begun.

My roses are starting to bud, but I’ve seen conflicting reports on whether to prune them back. What’s your advice? Also, what does renewal pruning mean?

Since buds are just forming, this is the time to prune stems to a little less than half the length of the branches and cut each one just above a newly emerging bud. New growth will begin on these fresh stems for the coming year. Roses can be maintained as shrub, multiflora, hybrid tea or miniature and will usually flower voluntarily throughout the growing season. If yours are hybrid tea varieties, they will grow new flowers each time you prune a faded flower. Cut the old branch just above where the leaf stem is growing a set of five healthy leaflets. It will grow a fresh bud from the location just below where the cane had a fading flower.

Renewal pruning means shrubs have grown too large and can be cut lower and narrower than they have become, which is usually successful with most overgrown woody shrubs. Check with your Cooperative Extension Service if there is a specific plant you wish to renewal prune.

The deer in McLean ate my viburnum and holly this winter. Is this normal?

There are viburnums and hollies that deer consume and some they don’t. They usually won’t eat those with thick or fuzzy (tomentose) textured leaves. Several I haven’t seen eaten by deer are leatherleaf, Allegheny, chindo and burkwood. I’ve seen our native arrowwood viburnum damaged badly. The hollies classically considered deer-resistant are perny, dragon lady and American holly. Horticulturists think this was because the thorny leaves were too painful to eat. At this point, deer have started eating plants previously considered deer-resistant. Theories suggest that if deer are hungry they will eat almost any plant.

We planted a row of 20 leyland cypress trees a few feet apart. These trees, some over 30 feet tall now, are problematic in heavy snowstorms. I can’t reach the upper branches to knock the snow off. Last year, heavy snow caused two to partially uproot. I was able to reset them using block and tackle and cabled them to adjoining trees. They seem to be surviving, but this year’s heavy snow caused a couple to bend. I was able to pull them upright, propping them with 2-by-4s, but the upper portions continue to droop. Your suggestions would be welcome.

You have received good longevity from these trees. It has cost you a great deal of labor to achieve this. The weather and where the trees are sited will determine how much longer they will offer screening. They need to be sheared into a pyramidal shape to grow strong branches, with tops pruned narrower than the bottoms so sunlight will reach the entire plant, including the area between the trees. This promotes strong branching so the trees can handle prevailing winds and snow loads. Otherwise trees will shade and weaken one another and lose foliage from lower limbs. Leylands have shallow root systems that predispose them to falling over.

Your leylands were planted too close together to grow foliage evenly around the trees, so 30 feet is the maximum height you should allow them to reach. Shearing their foliage and limiting their height will help them stand stronger. Open spaces between the healthiest ones. Achieve this by cutting down every other tree. Leave the strongest and remove the weakest. Shear branches to allow as much sun to reach the plants as possible to help them grow into stronger plants. I strongly recommend hiring a tree trimming company for the pruning. Visit garden centers and consider other trees to create screening in the event other leylands uproot.

I live in a homeowners association where some of the concrete parking pads in front of the homes have been replaced. The new ones are sloped at a lower angle than the old ones, and quite a bit of dirt and roots are exposed. We want to put up retaining walls. Is this a viable solution?

Make safety a primary concern for your homeowners association. The uneven soil and tree roots sticking out of the ground pose a safety risk. The soil needs to be leveled and the roots cut back to the soil to help alleviate areas that could cause tripping. Install pressure treated wooden ties, 6-by-6 inches each, stacked two high, and drilled and staked 24 inches into the soil. This would be a cost-effective way to retain soil at the parking pads. The area must be leveled and well-lit for the safety you desire. Also consider accessibility to the walkways leading to the front doors of the houses, which might require strategically placed wooden or concrete ramps to access parking areas.

The deer eat my plants. I have had good luck with mahonia, hemlocks and dragon lady hollies. Do you have other suggestions?

Deer’s palate of favorite plants changes continually, but here are some herbaceous and woody plants that I still think to be resistant to deer browsing. Perennials: black-eyed Susan, fern, brunnera, astilbe, hellebore, pachysandra and iris. Woody plants: lavender, rosemary, leatherleaf mahonia and Daphne. In certain areas, deer have begun to eat dragon lady hollies and nandinas.

Joel M. Lerner is president of Environmental Design in Capitol View Park.

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