Boxwood blight means avoid mixing old and new plants

Garden Q&A

  • Begonias are a worthy replacement for impatiens.
Begonias are a worthy replacement for impatiens. (Christine McComas, Baltimore…)
April 11, 2013|By Ellen Nibali, For The Baltimore Sun

People with old boxwoods are being warned not to plant new boxwoods nearby, but what about those of us with no boxwoods who want some? They're so deer-resistant.

The new and highly contagious boxwood blight disease has made it unwise, for the present, to introduce new, possibly infected plants into a landscape with old boxwood, especially historic boxwood. In your case, buying locally or Southern--grown boxwood would be the safest bet. Keep in mind that boxwood blight can infect both native and Japanese pachysandra as well as sweetbox (Sarcococca). Gardens with these plants, too, might want to delay new boxwood plantings until more is known about the disease. If anyone suspects their plants are infected with boxwood blight, immediately contact HGIC at 800-342-2507.

Last year, my broccoli had little green worms that I didn't notice until I got ready to cook it, and then I had to throw out my entire harvest. How can I avoid this?

There are a number of caterpillars that feed on members of the cabbage family. The velvety green larvae of the imported cabbage worm are most common. The adult is a little white butterfly with three black dots on the wings that you see flitting around all summer. Use row cover to prevent the butterfly from laying eggs on your plants. The caterpillars are well-camouflaged but easily handpicked. Bt, an organic insecticide, is effective for controlling young larvae. Later, you can use spinosad, neem or pyrethrum, all organic pesticides, too. The caterpillars have many predators and parasitoids that reduce their numbers drastically, so avoid using any broad-spectrum insecticides that harm beneficial insects and birds. And if you suspect some larvae slipped past you, simply soak your broccoli in salty water before cooking and they'll float up to be discarded. At season's end, remove plant debris where they overwinter.

University of Maryland Extension's Home and Garden Information Center offers free gardening and pest information. Call 800-342-2507 or send a question to the website at

Plant of the Week

Wax Begonia

Begonia semperflorens-cultorum

Many flower lovers were deeply worried after experts said to forgo planting impatiens this season. A new disease, impatiens downy mildew, devastated impatiens wallerina in most Maryland gardens last year. Infected stands went from blossoming beauties to nude stems in short order. What's a gardener to do? Impatiens are loved for being bright, carefree bedding plants for shady areas. Not to worry. A worthy replacement is wax begonia. This tender annual produces lush 10-to-12-inch mounds of cheerful pink, white, red and bicolored blossoms on fleshy stems through first frost. They prefer moist, well-drained soil but can tolerate dry conditions once established, and can take more sun than impatiens (especially the bronze-leaved begonias). Latest on the scene are lovely frilly double ones — great for containers.

— Christine Pfister McComas

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