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Garden Q&A

Butterfly bushes are invasive, but some varieties are less so

For The Baltimore Sun
Butterfly bushes are good for butterflies, but not caterpillars, and we can't have one without the other.

Are there butterfly bushes that are reliably noninvasive, in addition to the Lo and Behold types that are being marketed as sterile? I have seen Miss Ruby, Miss Molly and the Flutterby series listed as noninvasive, too.

These butterfly bush varieties tend to be smaller than the straight species and do set some seed, just a much smaller amount than the species — so they are not completely sterile. Keep in mind that the more plants of one species you have, the more genetic variation in the seed, and the greater the chances of seed viability. It's good you are following the issue of nonnative invasive species in Maryland. Of course, butterfly bushes provide nectar for adult butterflies but are not a good host plant for their caterpillars, and ultimately we can't have butterflies without caterpillars.

My privacy screen of 25-foot Leyland cypresses are thinning out and dying back, mostly at the base. The tops seem healthy. They were planted 7 feet apart about 25 years ago. What can I do?

Prune out dead branches. Most likely your Leylands have a cultural or environmental problem. Shading will cause these symptoms. Yours are planted close together and have grown closer; consider removing every other tree. Stressors such as drought cause trees to thin out, too, primarily the interior needles. Also, compacted soil, often caused by mowing on wet soil over the trees' roots zone, makes it difficult for roots to get water or oxygen. Leylands are also susceptible to at least three diseases, one of which — Cercospora needle blight — causes browning and dieback of lower, interior branches and moves up the tree. This disease is associated with wet weather or tight foliage that cannot dry quickly after it rains. For a more positive diagnosis, have an arborist certified by the International Society of Arboriculture look at the tree. They usually come out at no charge for an on-site diagnosis. Locate a certified arborist near you at treesaregood.org.

Digging deeper

Have long-winged insects — or just piles of wings — appeared in your home or porch? Do the insects walk more than fly, have wings that fall off and most simply die? They are the reproductive stage of termites known as swarmers or alates. Though most dry up harmlessly, they indicate a mature termite colony nearby. Your home should be inspected, then treated if necessary. To distinguish them from winged ants, think even and straight. Termite bodies are fairly even in width. The four wings are even lengths; the antennae are fairly straight. (In contrast, for winged ants, think uneven and crooked — sharply pinched waists, uneven wings, crooked antennae.) For more information, check the "Problems" tab on the HGIC website or see our pest control publications.

—Ellen Nibali

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University of Maryland Extension's Home and Garden Information Center offers free gardening and pest information at extension.umd.edu/hgic. Click "Ask Maryland's Gardening Experts" to send questions 24/7.

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