Issues → May/June 2007 → Home & Garden →
Real Solutions: leaf damage, violets, grass,
by Wayne Mezitt
The leaves on my blueberry bushes and crab apple trees are tattered. I notice lots of inch-long green caterpillars on the branches. What can I do to stop this damage? -- D.S., Hanson, MA
The leaf damage you describe is likely caused by the winter moth. This European pest has just recently become established in eastern Massachusetts. Its larva, the caterpillar you mention, feeds voraciously and can cause permanent damage to plants if unchecked after several years.
Adult winter moths appear in late November into December and then lay eggs on tree branches. As the eggs hatch in early spring, the tiny larvae crawl up the tree to "balloon" on thin strands of silk to other plants. Larvae wiggle their way into unopened buds to feed, later chewing new leaves that emerge from remaining buds. Be sure heavily defoliated plants receive adequate moisture as they put out their regrowth, and do not fertilize.
Some organic controls and certain chemicals can be somewhat effective, but because this pest has so recently arrived, few natural controls limit its damage. Researchers are working to develop lasting solutions, including introducing natural predators (visit umassgreeninfo.org to learn more about this). Check with your local garden center for the most up-to-date recommendations.
Violets are spreading through large sections of my lawn. I've tried numerous chemical control products, but none has made any impact on the violet leaves. Any suggestions? -- P.Q., Wilmington, VT
Violets, both perennial and annual, are difficult to eliminate once they become established in a lawn. Not only do they spread vigorously by seed and rhizomes, but they have waxy leaves that tend to shed any herbicide. They grow well even in shady conditions and are drought tolerant once established.
If you apply chemicals, avoid general herbicides (such as Roundup) that will kill everything they come into contact with. Look for formulations containing triclopyr, which has reportedly been effective, although repeated applications are needed. Use spot treatments that target only the violets themselves, and add a formulation containing a "spreader-sticker" for better leaf contact. Violets are most susceptible to chemical control in springtime when they are flowering.
One organic alternative would be to dig out the plants by hand, making sure you remove all the runners as well. You'll need to repeat the process as new plants appear, but over time your persistence will be effective. Another option is to let nature take its course and simply enjoy the violets. They're an attractive ground cover that looks good all summer, and they grow so densely that they choke out competing weeds.
I have a magnificent copper beech in my front yard, but the grass under it looks horrible where it used to be so lovely. What should I do? -- M.R., Milton, MA
Trees with dense crowns such as Norway maple, linden, and your European beech cast increasingly heavy shade as they mature, creating difficult growing conditions, especially for lawns. These big trees also utilize moisture and nutrients that lawns need to thrive.
Alternatives to maintaining grass beneath your tree include installing a mulched bed or planting one or more of the 25 woody and herbaceous ground covers that tolerate these conditions. I planted a mass of Siberian carpet cypress (Microbiota decussata) around the base of my own beech tree. This adaptable conifer tolerates dry shade, is hardy, and transforms into a purple-bronze color in winter to create a pleasing effect against the trunk.
-- R. Wayne Mezitt, Chairman, Weston Nurseries, Hopkinton, Massachusetts
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