Gardeners' Q & A
Orchids in Zone 6, delphiniums in the South, plant-growth enhancers and much more.
Q: Can I grow orchids outdoors in Zone 6?
A. Yes, one particular orchid can grow outdoors as a perennial in USDA Zone 6 and even Zone 5, if you use winter protection like mulch. Bletilla is an Asian native that grows up to 18 inches tall and produces a rosy-purple flower that lasts two to three weeks in late spring. To prevent rot, conditions require rich moist soil that drains well. The orchid can be expensive and hard to find in nurseries, so check with online and catalog sources.
Q: How do you keep plants from bolting?
A. Bolting is the process of going to flower. For certain vegetables and herbs, bolting is the last thing you want because it diverts energy from the production of foliage to the production of flowers and seeds. The plant stops producing foliage and what it does produce isn't flavorful. Cutting off the flower stalk will stop the problem temporarily, but in time the plant will send a replacement stalk. Warm weather is the No. 1 cause of premature bolting, so the best line of prevention is to plant early in the season.
Q: Why are you supposed to remove flowers from culinary herbs?
A. When herbs flower, they channel energy into flower and seed production, slowing the production of aromatic oils and other compounds that give herbs their desired and distinct flavors. You can slow or interrupt the process by removing flowers as they appear.
Q: What is a wetting agent?
A. A wetting agent is a surfactant, which is used to make various garden chemicals--such as fertilizers and pesticides--stick better to plant leaves. Typically a small amount is used, less than a tablespoon per gallon.
Q: What is Neem?
A. Neem is one of the greatest discoveries of the century for gardeners. An all-natural, multi-purpose pest and disease product, Neem is a garden chemical made from the subtropical Neem tree. Available in liquid concentrate or ready-to-spray form, Neem controls a number of fungal diseases and dozens of insects, from sod webworms to Japanese beetles and whiteflies. It is not toxic to birds, beneficial insects, animals or humans, but some plants can be sensitive to Neem so read the label carefully before using.
Q: Can gardeners in the South grow delphiniums?
A. Until recently, I would have said "no way." But recently growers in New Zealand introduced a new delphinium hybrid that can handle the heat and high humidity of the South. This plant requires the same growing conditions as other delphiniums--moist, well-drained soil and, especially in the South, no more than two to three hours of morning sun followed by shade the rest of the day.
Q: What can you tell me about so-called plant growth enhancers?
A. Plant growth enhancers truly do represent a whole new approach to pest and disease control. Most promising of all is the plant growth enhancer containing the bacterial protein harpin, which occurs naturally in most plants. Harpin helps stimulate a plant's defense and growth response, helping the plant grow stronger and more resistant to attack by pests and disease. Safe and effective on flowers, vegetables, trees, shrubs, and even lawns, plant growth enhancers may in time eliminate the need for pesticides and fungicides.
Q: Seen any neat tropical plants lately?
A. Yes, Acalypha wilkesiana 'Ceylon', also known as copper leaf. It's a Zone 10 tropical that makes a great patio or houseplant.