Sun-loving adenium needs a little encouragement to rebloom
Q: I have a 2-foot-tall adenium that is in great shape. It blooms beautifully but only once a year. What can I do to make it rebloom?
Will cosmos bloom continuously in our horrible summers? Do they grow well from direct-sown seeds?
Dave Sherron, Houston
A: Desert rose, Adenium obesum, is a heat- and sun-loving African succulent with pink, crimson, white or variegated trumpet-shaped flowers and prominently veined glossy foliage with downy undersides. The thick, bulbous base of the gray trunk (caudex) adds distinction to the plant. Desert rose is related to plumeria, oleander and vinca and contains a milky sap that’s poisonous when ingested.
Desert rose can be grown outdoors in beds in warm, frost-free zones, but is generally grown in a container here for easier winter protection in a warm, bright room.
Give a potted plant a half day or more of sun outdoors during warm weather. Water during the growing season, but make sure the soil drains well. Soil that’s kept too wet promotes rot. Keep the soil on the dry side in late fall and winter.
Desert rose needs time to mature and bloom. Flowering cycles generally come spring until fall.
Since your plant does flower at least once a year, encourage good growth and provide several hours of sunlight to encourage more blooms. Apply a balanced fertilizer a few times during spring and summer. Phosphorus may help boost flowering.
Cosmos are sun-loving, low-water, warm-season annuals from Mexico and South America. There are several species, but we typically grow two here that produce butterfly-attracting blooms spring-fall.
Yellow, orange and red cosmos, C. sulphureus, hold up in our heat in a sunny spot and in well-draining, light soil. Be sure to cut some blooms for indoor arrangements.
The long, narrow-lobed foliage differs from the finely cut leaves of C. bipinnatus, a species with white, pink, dark rose or lavender blooms. These pastels are favorites in my spring or fall garden, but I’ve not had the best luck with them in summer, perhaps because I’ve pampered them too much.
Cosmos grow 2 to 6 or more feet tall, depending on the cultivar. They reseed, but you can direct sow or add transplants in your garden for stronger stands.
Q: Is it too late to cut my holly ferns way back? The new foliage was nipped badly in the last freeze, and it would look best if I just whacked them back and started over. My concern is it is too late in the season for them to come back to any degree.
Virginia Hodge, Houston
A: I find holly ferns most resilient in our garden, and they have put up new fronds after I’ve been late cutting back the clumps.
If most of the fronds on your holly fern are burned it likely is easier to cut back the entire clump. I’ve tried removing only damaged fronds and leaving still-green ones, and that can be tedious, especially with a thick, mature clump. Pruning back an entire plant will leave a temporary “hole” in your flower bed, but new fronds will fill in nicely in warm weather.
Q: I have three terra-cotta hanging pots I would like to plant with something that won’t shrivel up and die when I’m out of town? They are on a balcony that gets morning sun.
Chris Greene, Houston
A: Fill the containers with a quality potting medium and plant when you are going to be in town for a while. Although the plants listed are on the low-water side, they will need moisture (but not soggy soil) until roots establish. Be aware that terra cotta breathes, and pots made of this material dry more quickly than plastic containers. You will need to water more often during summer. If you have downstairs neighbors, you’ll want to make sure water doesn’t run into their space.
If possible, move the containers into more shade while you’re away for several days to help prevent drying too much.
You may want to consider hanging the baskets so that you can enjoy looking at the plants, not just the bottom of the containers. This lower height also makes for easier watering. Apply a balanced, soluble fertilizer a few times during the summer to boost nutrients and create better-looking plants.
Warm-season moss rose and purslane are succulent trailing plants with vivid blooms. There are numerous sedums and other succulents such hen and chicks and kalanchoes (several types) and haworthias to use to create a textural container. Mexican sedum creates a thick mat of tiny needlelike plump foliage and has yellow spring blooms.
Silver ponyfoot or dichondra cascades beautifully from a basket. It looks nice flowing from a container with ‘Queen Victoria’ agave as a centerpiece.
Creeping jenny is a trailing plant with small, round chartreuse leaves.
Foxtail fern is a handsome plant that’s fairly indestructible. So is acorus, a grasslike plant with variegated leaves.
There are numerous bromeliads that clump and/or trail that might be suitable. Many neoregelias, billergias, aechmeas, canistrums and cryptanthus like morning sun.
Perhaps one of the verbenas would work. And vincas, available in several colors, loves our hot summers.
During the cooler months, petunias and calibrachoa can add color to your balcony.