Adenium is a perennial shrub native to parts of Africa. Commonly known as Adenium obesum or desert rose, this tropical, flowering beauty is often grown as a houseplant in the United States. Adeniums vary dramatically in appearance, leading scientists to debate the commonly held notion that there is only one species of the plant, according to an article by Dan Mahr, a horticulturist with the University of Wisconsin. Adenium is desirable for its ease of care and attractive flowers.
Adenium is a tropical plant. As such, it does not tolerate cold temperatures and can only be grown outdoors in United States Department of Agriculture (USDA) hardiness zones 10 and 11. For that reason, many home gardeners grow the desert rose in a container, moving it indoors when the weather becomes cooler.
Plant or place your adenium in a location where it will be exposed to a minimum of six hours of sunlight per day but preferably eight to 12 hours. Very hot, direct afternoon sun scorches the leaves of the plant, however, so a location that receives morning sun but filtered or dappled afternoon shade is best. Container plants stay small, but outdoor adenium can grow as wide as 5 feet, so give the shrub plenty of room to grow.
The desert rose prefers well-draining soil that is on the dry side. Outdoor plants prefer coarse soil. Indoor plants should be planted in potting soil mixed with equal parts perlite. The soil should not be bone dry, but the first 2 or 3 inches of soil should be dry before the plant gets more water. Three waterings per week during hot periods should be sufficient. In the winter, decrease the frequency of watering to allow the plant to go through a dormant period.
Blooming adeniums will thrive if fed in the spring. Once the plant begins to sprout new shoots, feed it a full-strength, balanced (10-10-10) liquid fertilizer every two weeks. In early summer, switch to one dose of a slow-release fertilizer formulated for palms. Repeat the dose of palm fertilizer in the fall. Do not fertilize over the winter while the desert rose is dormant.
Adeniums can get quite leggy if left to grow naturally. Prune off new shoots when they sprout in the spring if you would like to train the shrub to only a few trunks. This will also encourage stronger blooming. Use extreme caution when pruning, because the sap of this plant is very poisonous. Wear protective gloves and wash all tools immediately after pruning. Keep the plant out of reach of pets and children.