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DIGGING IN
By Scott Aker
Special to The Washington Post
Thursday, May 11, 2000; Page H11
Q: What's happening to my rosemary bush? It has survived outdoors for several years but now has horrible brown bumps on some of the stems, which are dying back. What is it, and what can I do to fix it?
A: Normally, bitter winters are rosemary's worst enemy. Lately, the odd symptoms that you describe have become quite common in the absence of winter dieback. The damage probably can be blamed indirectly on last year's drought.
Rosemary is superbly adapted to drought, but it is not adapted to sudden changes. In its Mediterranean homeland, it gets little rain and blistering heat all summer, while winters are moist, cool and mild.
Heavy watering in the midst of a drought can send rosemary into shock. Waterlogged soil may kill roots or lead to root rot, impeding the plant's ability to take up moisture. The water-starved branches turn olive green and then dark brown before dying.
Even if there is no root rot, a sudden surge of water taken into the plant may rupture living cells in the stems and leaves, a condition called edema. Callus grows to replace the disrupted cells; this knobby callus looks like the start of new roots along the stem.
The warty stems conduct water poorly, and the foliage inevitably browns and dies.
Cut back any branches that are in poor health this spring. Plant rosemary in quick-draining sandy soil if possible and avoid a soil high in organic matter. Allow it to weather drought on its own; do not water it frequently in hot, dry weather.
Q: I have a new house on the Chesapeake Bay. The lot slopes steeply down to a creek, and the soil is very loose, dry and sandy. I plan to be at the house for two or three weekends a month. I planted some flowers last year, but most died without someone to care for them during the week. What can I plant that will take care of itself and give me lots of color during the summer?
A: Several plants fit the bill. In sunny areas, try the hardy ice plant, Delosperma cooperi. It loves heat and weathers drought well, spreading as much as two or three feet in a favorable growing season.
Red-hot poker (kniphofia) is a bold perennial with grasslike leaves and brilliant torches of orange flowers that is at home in almost pure sand.
Penstemon and pink evening primrose are happy in dry conditions, and you could even plant the native prickly pear cactus, Opuntia humifusa.
If you need a backdrop to a perennial planting, you may want to use bayberry or holly osmanthus. Fill in with some annuals like gaillardia and California poppy to provide an additional boost of color when the perennials are not in bloom.
Q: Do you have any suggestions for an evergreen vine that will grow on a chain-link fence?
A: There are lots of annual vines that can be grown on a chain-link fence, but the list of hardy evergreen vines that are not too invasive, like Japanese honeysuckle or English ivy, and not too heavy, like magnolia vine, is extremely short.
I would probably plant the bright-yellow-flowered Carolina jessamine, Gelsemium sempervirens, and I'd probably choose the double-flowered Pride of Augusta because it seems to be hardier than most. The small evergreen leaves, fragrant spring flowers and thin, wiry stems would harmonize well with a chain-link fence without overwhelming it or causing the fence to sag.
Carolina jessamine can be successfully grown in full sun or partial shade; it benefits greatly from some protection from winter winds if planted north of Washington.
Scott Aker is a horticulturist at the U.S. National Arboretum.
Have a question about gardening? Write Digging In, Home Section, The Washington Post, 1150 15th St. NW, Washington, D.C. 20071 or e-mail home@washpost.com.
TIP OF THE WEEK
PRUNE BACK OVERGROWN winter jasmine, forsythias, lilacs and flowering quince shrubs now, before buds are set for next year's flowers. Rather than shear the bushes, remove up to one third of older stems entirely.
© 2000 The Washington Post Company
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