Several factors are dimming the glow-worm population

Backyard Q&A

August 28, 2005|By Jon Traunfeld and Ellen Nibali | Jon Traunfeld and Ellen Nibali,Special to the Sun

What is the prevalence of Lampyris noctiluca (glow worms)? I have just seen a half-dozen this evening.

Glow worms, though not yet an endangered species, are dwindling overall in population for some expected and unexpected causes. The continued destruction of wetlands impacts their population, and the increased use of night lighting has a negative effect on the insects' reproduction activities. Consequently, fewer "lightning bugs" (the flying male) and "glow worms" (the wingless female) are observed in urban and suburban settings.

Also, because the insects spend a lot of their life in turf grass, evidence suggests that the increased (usually unnecessary) use of pesticides in suburban lawns has had a detrimental impact on the insect's population. Greater numbers this year are probably due to ample rainfall. For further research visit SCIRUS, under our Web page's General Interest links.

Our 3-year-old Nikko Blue hydrangeas didn't bloom this year. In March 2004 I cut down all of them to about 3 inches, which I read is the time to do so. Later I read that they only bloom on old wood. How do I know what is "old wood" versus "new wood?"

As you discovered, big leaf hydrangeas are an exception to the rule to prune summer-blooming shrubs in the spring. These plants bloom from "old wood," i.e., woody stems grown the previous summer. ("New wood" means young, flexible shoots grown during the current season.) Hydrangea flower buds set on old wood at the end of summer after the plant flowers.

A fatal mistake is to prune off all the old wood in the spring and remove all the flower buds. The only time you can safely prune the live tissue, without removing buds, is immediately after flowering ends and the blue flowers fade. Because the fading flowers remain highly decorative, most people elect to not prune then either. Consequently, always plant a hydrangea where it has enough room to grow and doesn't need to be pruned at all.

Jon Traunfeld, regional specialist, and Ellen Nibali, horticulture consultant, work at the University of Maryland Cooperative Extension's Home and Garden Information Center. The center offers Maryland residents free gardening information and answers to plant and pest questions. Call its hot line at 800-342-2507 (Monday through Friday, 8 a.m.-1 p.m.) or e-mail questions to (You can also download or order publications and diagnose plant problems online.)


1. Keep herb plants clipped to keep them bushy.

2. You may see large numbers of soldier fly larvae in your compost pile, especially if the pile is wet. These large, beige-colored maggots are part of the compost food web. The adult flies are beneficial insects.

3. Bait stations are very effective at controlling ants indoors and outdoors. For persistent indoor-ant problems, have the species identified to determine the best course of treatment.

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