Screen Your Bamboo Carefully
AI would recommend bamboo only if you stick to the clumping types and avoid the more common running bamboos. Running bamboos create more friction between neighbors than any other plant, because their spread cannot be controlled unless elaborate precautions are taken. It is also impossible to use herbicide to kill a portion of a clump that is straddling a property line.
Umbrella bamboo, Fargesia murielae , is by far the most successful and popular of the clumping bamboos that can be grown in the Washington area. Because it is a clumper, it has a vase shape that is broader at the top and gracefully weeping at the ends of the branches. Although it can be used as a screen, it is best used more informally with other evergreens in a mixed planting. To grow well, it requires some shade, particularly in the heat of the afternoon. In a shady spot, you can combine it with winter-hardy camellias and hollies to give you some texture contrast and seasonal interest.
If you have full sun, your bamboo choices are really limited to the running types, but plant appropriately scaled trees instead. If you are willing to consider deciduous trees, your choices grow considerably.
I have zebra grass. How and when should I fertilize it?
Most ornamental grasses do well on average soil without additional fertilizer. In fact, excess nutrients may lead to rampant growth of the clump, producing an outer ring of vegetation and a hollow center. As a result, you may have to undertake the laborious task of dividing your clump, especially if it has no space to grow.
Let the grass tell you if it needs some fertilizer. If the leaves are deep green, it flowers well and appears to be healthy, skip the fertilizer. If it grows slowly, is chronically yellow and seems to lack vigor, a handful of slow-release fertilizer may be in order, but only if dividing it and replanting it fails to increase its vigor.
My Bakerii blue spruce has been losing its needles on its leader and other branches and generally looks sickly. It does have bagworms. I remove the ones in reach, but what about the others?
If you can’t spray the trees, your options are very limited. The ever-popular pesticide known generically as acephate is available for use on trees in the form of Bonide Systemic Insecticide Bullets, but you have to drill holes in the trunks of the trees to insert the insecticide cartridges. The resulting wounds can compromise the health of the trees and may be an entry point for wood-decay organisms.
You also can contract with an arborist to have the trees sprayed when the hatchling bagworms emerge, usually around late June or early July in our area. If they are sprayed shortly after they hatch, a pesticide containing Bacillus thuringiensis would be effective. Spinosad is another good option for control of bagworms and will control even the fully grown caterpillars as long as they are still feeding.
If evergreens are completely defoliated by bagworms, they seldom recover. You might want to assess the trees to see whether you need to invest your effort into replacement of the trees or treatment of the bagworms.
Scott Aker is a horticulturist at the U.S. National Arboretum.
Have a question about gardening? Write Digging In, Home Section, The Washington Post, 1150 15th St. NW, Washington, D.C. 20071; fax 202-334-5059; or e-mailhome@washpost.com.
