Q: I have a photinia (red tips) hedge that has grown so high that it is no longer bushy. If I cut them back to, say, 6 to 8 feet high (or lower) will they bush out again?
Rachel Castle, Hillsborough
A: Red tip photinia (Photinia x fraseri) is very tolerant of pruning and can be cut back fairly severely without harming the plant, but there is a significant catch. Red tip is a pretty easy plant when allowed to grow without much pruning but when it is cut back, the tender new growth is exceptionally susceptible to a fungal leaf spot disease that can defoliate your entire hedge. Fungal sprays can be used to control the disease, but fungicides can be quite toxic and are best avoided when possible. This fungal disease is why the once-ubiquitous red tip is no longer so commonly grown. I’d recommend removing the photinia and replacing it with something else.
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Canna lilies that will not bloom
Q: I have some beautiful canna lilies in a bed with junipers and black-eyed Susans. While I enjoy the cannas’ burgundy foliage, the plants rarely bloom. What can I do to encourage more?
Dottie Hudyma, Rocky Mount
A: The three reasons canna lilies will stop flowering is typically because they are in too much shade, they have become overcrowded or they need fertilizer. If your plants are growing with junipers and black-eyed Susans, you likely have plenty of sun. I would dig your plants now and divide the thick rhizomes and replant the youngest and healthiest portions. In spring, after growth starts, fertilize your plants with a general purpose fertilizer. Your plants should flower well by summer.
Can you delay a Christmas cactus’ blooming?
Q: What do you need to do to get a Christmas cactus to bloom at Thanksgiving? It started to bloom around two weeks before Thanksgiving and will not have any blooms left by the holiday.
Adele Kaplan, Raleigh
A: I’m sorry I didn’t get you an answer before the holiday but hopefully this will help you for next year. Thanksgiving and Christmas cactus are two different but very similar plants. The former flowers in the late fall and the latter a month later. You can tell the difference by flowering time and the margins of the flattened leaf-like stems. A Thanksgiving cactus will have jagged, pointed margins, while the Christmas cactus will have rounded edges. Cool weather and longer nights will instigate flowering for both. If you keep a plant where it stays too warm or if it gets light all night, the plant will often not bloom at all. Putting a plant outdoors or by a cool window where the temperature drops to around 50 degrees (but not below about 40 if outside) and ensuring a long, uninterrupted dark period will get it in bloom. To delay flowering, keep your plant warm and provide some night-lighting until you are ready for it to begin setting flower buds.
Mark Weathington is the director of the JC Raulston Arboretum at N.C. State University in Raleigh. Info: jcra.ncsu.edu. Please send your gardening questions, and the city where you garden, to: email@example.com.
Common name: Poet’s Laurel
Botanical name: Danae racemosa
Family: Asparagus (Asparagaceae)
Category: Evergreen sub-shrub
Primary uses: Shade gardens
Dimensions: 24 to 36 inches tall by 36 to 40 inches wide.
Culture: Partial to full shade. Prefers a moist, well-drained. organic, woodland soil. Once established, it will tolerate considerable drought. It has very few pests. Old stems can be cut back to the ground in late winter if they have suffered any cold damage. It is extremely slow to grow into a sizable plant from seed, but mature plants can be divided in spring or fall.
Bloom time: Spring
Color: Greenish-yellow, not showy
Hardiness: Zero degrees (USDA hardiness zone 7)
General attributes: Poet’s laurel is highly prized by florists for its glossy evergreen leaves (technically modified stems), which hold their color for a very long time when cut. In the landscape it is a valuable addition to the shade garden where the gracefully arching branches and bright orange-red fruits add color and elegance.
Ask a question, win a book
We’re trying to encourage readers to send in their gardening questions. So if you send a gardening question for the monthly Ask the Gardener column by Dec. 31, you’ll be entered for a chance to win a gardening book.
These titles are up for grabs: “Saving Vegetable Seeds,” by Fern Marshall Bradley; “Fairy Gardening,” by Julie Bawden-Davis and Beverly Turner; “Year-Round Indoor Salad Gardening,” by Peter Burke; and “Veranda: The Romance of Flowers,” by Clinton Smith.
The deadline to submit your question and be entered to win a book is noon Dec. 31. Please send your gardening question, including the city where you garden, to: firstname.lastname@example.org.