Where Have the Butterflies Gone?

By Joel M. Lerner
Saturday, August 16, 2008

Here are answers to some of your summer gardening questions.

Q: Where are the butterflies? In past years, the yard has been full of them, beginning in early spring. This year, there are two or three at a time, and they have just begun to appear. There is little variety. What's up? -- Lynn Kibler

A: I have been wondering the same thing. Biologist Arthur Shapiro of the University of California at Davis, who has been studying butterflies as a career and hobby for almost 40 years, has noted a decrease. According to the National Wildlife Federation, other lepidopterists share Shapiro's concern. Worldwide, many butterfly species have begun to falter and disappear. In this country, the Fish and Wildlife Service has designated 23 species as endangered or threatened.

This is more than an aesthetic loss. Butterflies play a key role in plant reproduction, transporting pollen from flower to flower. They provide food for birds and other insects. Loss of habitat is a primary cause for their decline.

You can help.

To attract butterflies, you need host plants on which adults will lay eggs. Host plants feed caterpillars, which usually pupate on them. When they emerge as butterflies, they are able to drink and mate. They need nectar plants and small, shallow puddles of water for drinking. Some host plants for various butterflies are spicebush, sassafras, oak, plum, wild cherry, willow, ash, milkweed, daisy, aster, fennel, parsley, verbena and snapdragons. There are many nectar plants. Black-eyed Susan, cosmos, butterfly weed, goldenrod, joe-pye weed, lantana, lavender, purple coneflower, salvia and verbena are just a few. Contact the National Wildlife Federation ( http://www.nwf.org) for more information.

I would like to plant a butterfly garden, but I live on the sixth floor with a balcony overlooking a major city street. Do you think butterflies would fly that high in an urban environment? -- Marie

Rooftop gardens have done much to attract butterflies and birds in urban environments many stories above ground. So it would stand to reason that a sixth-floor balcony garden has the potential to do the same. Butterflies taste with their antennae, tongue and feet, giving them an extraordinary ability to detect nectar plants. A balcony garden can provide nectar for both butterflies and hummingbirds. Petunias, for example, are a desirable nectar plant for swallowtail butterflies, which seem to be the only butterfly with tongues long enough to reach the nectar. Hummingbirds also go crazy for petunias. The main requirement for the plants is good sunlight, seven hours or more.

Butterfly nectar plants are listed in the answer to the question above. Several good hummingbird plants are goldflame honeysuckle ( Lonicera heckrottii), golden honeysuckle ( L. flava), trumpet vine ( Campsis radicans) and shrimp plant ( Justicia brandegeeana), commonly grown as a houseplant but great on a patio. Use fiberglass containers, less porous than ceramic, and keep plants moist and well drained. Use two inches of packing peanuts covered with landscape fabric in container bottoms to provide good drainage. A soilless potting mix will keep containers light enough to move.

My butterfly bush did really well. I kept cutting back spent clusters of flowers. I now have more spent clusters than new ones. Would it be okay to prune it back hard? I would like to keep it blooming because I'm beginning to see quite a few butterflies. -- Marianne Lymn

Cutting back faded flowers is the most desirable way to maintain butterfly bush ( Buddleia davidii). It is so prolific that the thousands of seeds it produces will self-sow in any sunny, moist nook or cranny. It could germinate in cracks of walls or walkways or any bare patch of soil. It is considered one of England's most invasive alien shrubs and has the same invasive reputation in its native China. In the past decade, it has made the invasive-alien-plant list in the United States. Continue to deadhead the shrub in any way necessary. If flowering is so profuse that selective pruning is too time-consuming, use shears to remove spent flowers before they go to seed. It will repeat-bloom on new growth within several weeks.

What blue hollies do you recommend for a slow-growing variety that will reach six to eight feet and be tolerant of the climate in the Washington region? Is there a difference with regard to cold resilience? What about differences in color? Should we use blue boy, blue girl or blue princess? -- Valeria

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