Desert rose (Adenium obesum) takes well to life indoors, thriving in dry air and year-round warmth. This desert succulent flowers in summer and fleshy green leaves remain year-round unless subjected to stress. Desert rose grows outdoors only in the warm climates of U.S. Department of Agriculture plant hardiness zones 10b through 11. It is a near perfect indoor plant with one exception: The sap is toxic. Take care to keep the plant away from pets or children who may break off and chew on the branches or leaves.
Keep It Warm
To get the best growth and flowering, keep the temperature between 75 and 95 degrees Fahrenheit year-round. Desert rose tolerates temperatures between 55 and 75 F and can survive temperatures as cold as 35 F. When the air temperature drops below 55 F, it triggers stress which often manifests as unsightly leaf loss and leaf yellowing.
When positioning a desert rose indoors, give it a spot out of drafts, especially in winter and keep it away from heater or air-conditioning vents.
Desert rose can survive a drought but suffers if kept too wet. Water thoroughly when the top 2 to 3 inches of potting soil mixture dry out. Checking the soil for dampness is the best way to determine when to water as frequency varies depending of container size, indoor temperature and humidity. Pour the water into the container slowly adding more until it starts to leek from the drainage holes. This is the best way to make sure the soil is thoroughly damp.
Potting For Root Health
Good drainage is key to keeping a desert rose plant healthy and happy indoors. Use a container that has at least one drain hole in the bottom. You can set the pot in a saucer to catch excess water and protect your furniture, but make sure you empty it whenever it has water in it. A standard potting soil mixed 1/3 with perlite or clean sand is best for this desert-dwelling plant.
Fertilize During Flowering
Fertilize a desert rose plant once a week starting in late spring and continuing through the summer blooming season. Use 1 teaspoon of standard liquid houseplant fertilizer mixed with 1 gallon of water. Pour the water over the soil -- schedule fertilizing to coincide with watering when the soil starts to dry out -- until it penetrates to the bottom and starts to leak out the drain holes. If the fertilizer solution isn't enough to thoroughly wet the soil, use additional plain water.
Pests and Solutions
Occasionally, mealybugs and spider mites show up on desert rose plants growing indoors. Mealybugs are small white insects that cluster like pieces of cotton on the branches and leaf undersides. Spider mites are tiny bugs that feed in colonies. Often, you will notice a fine weblike structure on the affected leaves.
Use a mild dilution of detergent in water to wash off and control both spider mites and mealybugs. Mix 1/2 a teaspoon of dishwashing detergent -- look for one that doesn't have degreasing agents as it can damage the plants natural oils -- in 1 quart of water. Dampen a cotton cloth or a cotton swab in the diluted detergent and use it to wipe off the insects. Remember to look under leaves for any that are hiding out. Repeat as necessary until the infestation clears.
Trim to Shape
Annual pruning encourages bushy growth -- these shrubs can get leggy when left alone. Ideally prune in early spring before the first flower buds appear, but a trim anytime of year won't hurt this hardy houseplant. Cut back any tall, lanky stems the approximate height of the rest of the shrub and prune to control the size and shape.
Warning: Discard all the clippings, including stray leaves and twigs in the garbage away from children and pets. Desert rose has toxic sap just under the thin bark. Wear gloves when handling or pruning. Dip your shears in a solution of equal parts rubbing alcohol and water after pruning to sterilize the blades and minimize the potential of spreading disease to other indoor or outdoor pants.