Q My wife and I just built a house and are having trouble finding a tree that will fit in the three-sided courtyard leading to the front entrance. We would like to plant three trees on either side of a central path, each in front of a window. They would be spaced 10 feet apart. We like the columnar hornbeam, but are worried they would eventually overwhelm the area. Any suggestions? What if we planted the trees in containers and sank the containers in the ground -- would that slow growth and prevent the trees from growing too large?
A Fastigiate European hornbeams might work well at first, but as they reach maturity they will be far too large. Fully grown trees reach 30 feet in height with a spread of 15 feet. A tree in a sunken pot might be stunted for a while, but you are taking the considerable risk that none of the trees will break loose of its shackles in time.
If you like magnolias, Little Gem southern magnolia grows to 20 feet with a spread of 10 feet. The leaves are a bit smaller than those of most southern magnolias, but the overall texture is still somewhat coarse. If you want something fine-textured, plant some bay. Bay (Laurus nobilis) is not normally hardy in our area, but a variety known simply as Hardy has sailed through subzero winters with no damage. You can get it by mail order from Triple Oaks Nursery (www.tripleoaks.com, 856-694-4272). This form is very upright and won't require any pruning to keep it tidy.
I have some lovely azaleas, but two old ones seem to be turning black. I guess it is some sort of fungus. Can you suggest a remedy?
Your azaleas are turning black because of a fungus called sooty mold growing on honeydew excreted by insects feeding on the shrubs. The culprit, most likely, is an insect called the azalea bark scale. Look closely near the juncture of the branches and you may see small white fuzzy bumps. It takes very few of these to produce a lot of honeydew.
Spraying with the wrong pesticide at the wrong time may actually make it worse, because you will be killing the scale's natural predators and parasites. One of the most effective pesticides for this particular insect is imidacloprid, which is found in the Bayer Advanced line of lawn products. Apply it to the root zone according to label directions in early spring. The problem should diminish during the coming growing season.
If you want to pursue a softer approach, you will have to pinpoint the emergence of the mobile crawler stage of the insect, generally late spring and late fall. Tap infested branches over a piece of paper and examine with a magnifying glass. If you see the soft-bodied crawlers, spray the plant thoroughly with a 1 percent solution of horticultural oil. You may need to treat the plant several times before the scale insects are gone.
I have a small garden space with about four hours of sun per day. I want to grow annuals for cutting. I suspect zinnias will grow too tall due to sun conditions. Please suggest substitutes, preferably seeds or plants available locally.
Cutting gardens are best placed in full sun. A mere four hours of sun is not enough for most plants that are good for cutting.
It is possible to grow a few plants for cutting in your garden such as the old-fashioned, annual touch-me-not (Impatiens balsamina). Consider shade-tolerant perennials such as variegated Solomon's seal and large flowered Honeybell hostas. Hosta leaves make a bold statement in the vase as well. Wood hyacinths also do well in partial shade, and the flowers are good for cutting.
Scott Aker is a horticulturist at the U.S. National Arboretum.
