Real Solutions: leaf damage and grass under trees

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.

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