Q: Large dahlia flowers have been a favorites of ours. How well do they grow in Central Florida and what care is needed?
A: Dinner-plate-sized dahlia blooms, as well as smaller ones, have been favorites of many gardeners — especially those moving here from the more-northern states. But locally they can be a challenge. Dahlias don’t like the summer heat and humidity. Plus they don’t overwinter in the ground or as stored tubers. Gardeners with fond memories of dahlias wanting to give them a try should obtain tubers available at local garden centers or mail-order suppliers. Plant the tubers in a well-drained, soil improved with organic matter of compost and manure. Keep the new growths moist and fertilize with a slow-release product as instructed on the label. Plants need a trellis or staking for best growth and flowering. Enjoy the blooms on the plants or use them in bouquets. Regretfully, dahlias struggle during the rainy season and decline. They have to be replanted the following spring.
Q: I have a frozen seedling avocado tree about 12 feet tall. Some say to leave it alone and it will grow back and others say cut it back four or more feet. What should I do?
A: Maybe a combination of the well-meaning advice can help you determine the extent of freeze damage and potential survival. Your real chore is to find out how far back along stems and trunks the avocado has been frozen. Use a knife to scrape the stems and trunks looking for green tissue below the outer bark. Trunk tissue may be greenish to light brown and moist. If the limb and trunk tissue is dark brown and dry it is dead. When you can determine how far down limbs and trunks are dead, you can then do the needed pruning. Prune back below the dead portions, which may be four feet or to near the ground. Since this was a seedling tree, any growth from the base should produce a tree like you remember.
Plant Doctor: A durable addition to home and garden, this begonia a star with or without flowers
Q: Azaleas seem to be producing lots of blooms and growing well this year. Should I use them as replacements for shrubs that have been frozen?
A: One thing the February cold did was encourage good azalea blooms. Azaleas like the chilly to cold weather as it seems to mature the flower buds, helping them open uniformly to produce great displays. Azaleas have been favorite shrubs but fell out of favor in recent years due to their cultural requirements. If you’re thinking of replacing frozen shrubs with azaleas, make sure you are replanting in an acidic soil. Have the soil pH checked and if needed apply an acidifying product like soil sulfur as recommended through a soil test. Adding organic matter and pine bark fines to the soil can also make it more acidic. After the soil is improved, add the azaleas and keep the root balls moist with frequent waterings. It takes about a year or two of consistent care for azaleas to become established in local soils.
Q: We would like to seed a sandy backyard. Do we add organic matter to the soil first?
A: Sandy soils seem to absorb organic matter, which makes it of limited value when starting a new lawn. It won’t hurt to till in several inches of organic matter, such as well-decomposed compost or peaty materials, but in a few months the soil is back to mainly sand. Probably it’s more important to till the soil before planting to mix the upper layers, four to six inches deep, and adjust the soil acidity if needed. Then concentrate on keeping the soil moist during gemination and establishment of the new lawn.
Q: Tree-sized yellow, flowering landscape plantings have been in bloom for a few weeks. What is this tree and when can one be planted?
A: Showstopping yellow tabebuias have been in bloom since late February. If you remember, there was a pink tabebuia in bloom during January and until the February freeze. Yellow tabebuias are cold sensitive but it appears the buds were dormant enough to resist damage. Yellow tabebuias are of several types or species. Find your new tree at local garden centers but be sure it’s one with some cold tolerance. Now is a good time to add a tabebuia to the landscape. They can be planted in a sunny spot throughout the year.
Q: Our amaryllis plants have finished blooming. How do I care for the plants and the remaining flower stalk?
A: Help your amaryllis plants flower again in about a year by keeping them in containers or adding them to lightly shaded garden sites. Most amaryllis plants grow well in 6 inch or larger containers filled with a good potting mixture. Fertilize with a slow-release product following label instructions. Usually a fertilizer application is needed in March, May and August. Keep the soil most through summer and then allow the surface to dry before watering during fall and winter until flowering. Most gardeners remove the thick flower stalk by cutting it off as it enters the cluster of leaves. If it’s producing a seed pod, some leave the stalk until the pod turns brownish and the seeds are ready to sow. If you want the fun of growing more amaryllis, the seeds are easy to germinate but take about three years to grow a flowering bulb. After the seeds are harvested the stalk is removed.
Tom MacCubbin is an urban horticulturist emeritus with the University of Florida Cooperative Extension Service. Write him: Orlando Sentinel, P.O. Box 2833, Orlando, FL. 32802. Email: TomMac1996@aol.com.
