Adenium obesum, commonly known as the desert rose, is a perennial flowering shrub succulent that is native to the African continent. A relative of the oleander, it is an extremely low maintenance plant the grows pink, cerise or white blooms in summer. It is very sensitive to cold temperatures and is hardy only in USDA Zones 10 and 11. When planted in a large container, desert rose can be moved indoors when temperatures dip below 50 degrees Fahrenheit.
Choose a sunny location for your desert rose that receives full sun and afternoon shade in hot and dry climates. Plant adenium at intervals that will accommodate their mature spread of 5 feet to reduce the need for pruning and to prevent the plant from having to be dug and moved.
Fertilize just once a year in the spring with a general purpose water soluble fertilizer. Follow the label directions and err on the side of under-fertilizing, as adenium is not a heavy feeder. Apply the diluted fertilizer over pre-watered soil to prevent burn and speed the uptake of nutrients. Amend the soil with ground lime to raise the alkalinity to the ideal level of between 7.0 and 7.5 pH.
Water consistently throughout the growing season so that the soil is uniformly moist when reaching a finger down an inch or so into the soil. Scale back watering in the winter to compensate for rainfall and prevent over-watering and rot.
Control for aphids should they appear on your desert rose by simply washing them off with a strong stream of water from your hose, fitted with an adjustable spray head. Carefully aim the stream of water onto the stems, avoiding the flowers themselves, if possible. For intense aphid infestations, spray on an insecticidal soap according to label directions. Refrain from over watering, which can cause basal rot. If you notice a softening of the fleshy trunk in spots, reduce watering and always water around the drip line of the shrub so the immediate soil area around the trunk is not soaked.
Prune your desert rose sparingly to control its shape and size as needed. It does not require pruning for growth or bloom. Always don garden gloves when cutting and handling the desert rose to protect your hands from the toxic sap and discard the cuttings in the trash, bypassing the compost bin.
Transplant or repot your adenium obesum when the container begins to inhibit its top growth and the soil is depleted. Very carefully slide the shrub out of its container without snapping its delicate succulent roots. Place the shrub into a new container at least half again the size of the root ball and at the same planting depth the shrub is accustomed to. Fill with a good quality commercial potting soil and water it well. Add more soil if needed to fill in pockets and water lightly a second time to settle all of the new soil.