Garden Column for the Salisbury Post

Darrell Blackwelder

June 21, 2006

      Driving at the coast a few days ago with my car window down, I had the opportunity to experience a truly fragrant southern plant-the gardenia. Gardenias were in full bloom and the odor was divine.                                        

      Gardenias are very popular shrubs in Rowan County, one of my wife’s favorites. But these truly southern shrubs are not the easiest shrubs to grow, but their exquisite white, fragrant flowers make up for the extra care.                                     

     Gardenia jasminoides or common gardenia is an evergreen shrub that varies in heights from 2 to 6 feet, depending on the variety with its spread is generally about the same. The plant has a medium growth rate with glossy, dark-green foliage 2 to 4 inches long and half as wide. The flowers are waxy, white although some cultivars may be yellow. The bloom can be single or double and up to 4 inches in diameter depending on the cultivar. The flowers bloom over a long period of time, from May through July and are very fragrant.         

     Gardenias grow best if planted in filtered or light shade with no competition from tree roots. The shrub also does well as a potted plant. Gardenias prefer acid, moist, well-drained soil with plenty of organic matter.                                                                      

     Mulch gardenias heavily and apply fertilizer in mid-March, using an azalea plant food, fish emulsion or blood meal and again in late June to encourage extra flowers. It is very important not fertilize gardenias in late summer or early fall. Late fertilization stimulates tender growth of this and other cold sensitive shrubs. Gardenias are often killed when winter temperatures drop below 15 degrees. Irrigation is necessary to keep the plants in good condition which enables the plant the ability to withstand winter weather.                       

         Gardenias are not without problems. Sooty mold is a black mold that coats gardenia leaves which is usually due to an infestation of aphids or whiteflies. While eating, they excrete excess moisture in the form of honeydew and this, in turn, supports the growth of a black fungus. I have used insecticidal soaps and summer oils successfully to control both aphids and whiteflies.

     Below are cultivars available at local nurseries.

• ‘August Beauty’ grows 4 to 6 feet high and blooms heavily from mid-spring to fall.
• ‘Chuck Hayes’ is an extra hardy type to 4 feet high with double flowers in summer.
• ‘First Love’ is larger than ‘August Beauty’ with large flowers in spring.
• ‘Golden Magic’ reaches 3 feet tall and 2 feet wide, and has golden yellow flowers.
• ‘Kleim’s Hardy’ is hardy to 10 ° F and grows to 3 feet tall with single flowers in summer.
• ‘Mystery’ is the best-known selection. It has 4-to 5-inch double white flowers and can reach 6 to 8 feet.
• ‘Radicans’ grows to only 12 inches tall and spreads 2 to 3 feet, with small, dark green leaves and inch-wide double flowers in summer.
• ‘Daisy’ is a more cold hardy variety recommended. 

Darrell Blackwelder is an agricultural agent in charge of horticulture with the North Carolina Cooperative Extension Service in Rowan County. For archived garden columns or other information, visit the Rowan County Master Gardener web site at www.rowanmastergardener.com,e-mail Darrell_Blackwelder@ncsu.edu