Few plants are as iconic in the succulent collecting hobby as Adenium obesum. More commonly known as the Desert Rose, this species has an attractive caudex and funnel shaped flowers, making it a worthy addition to any plant collection. For us in South Africa, these plants are particularly special because several members of the Adenium genus call our country home.
While often compared to its cousin the ‘Impala Lily’ or ‘Sabi Star’ (Adenium multiflorum), Adenium obesum is the more widespread species found throughout tropical and subtropical Africa. It is a slow growing but incredibly rewarding plant that can live for decades, if treated with a little respect for its natural growth cycle.
Understanding the Caudex of Adenium obesum
The most defining feature of a Desert Rose is the caudex. This is the thickened, bulbous base of the stem that functions as a water storage organ. In its native habitat, this allows the plant to survive long periods of drought. For the grower, the caudex is where the personality of the plant lies. No two plants grow exactly the same shape. Some develop tall, bonsai-like stems, while others stay short and widen at the base.
Light and Temperature Requirements
If you want your Desert Rose to thrive, you must give it sun. To produce the famous pink and white flowers, this species requires at least six hours of direct sunlight every day.
Temperature is the other critical factor. Adenium obesum loves the heat and performs best when temperatures stay between 20Β°C and 35Β°C. However, they are extremely sensitive to frost. If you live in an area with cold winters, such as the Highveld, you must bring your plants indoors or into a protected greenhouse once the night-time temperatures start to drop. Even a light frost can cause severe damage to the soft tissue of the caudex.
The Art of Watering Adenium obesum
Watering is where most growers run into trouble. During the active growing season, which runs from September through March in South Africa, these plants enjoy regular watering. You should wait until the soil has dried out completely before drenching it again. It is important to thoroughly soak the soil, as only giving it a small amount at a time is not sufficient.
As autumn arrives and the days get shorter, the plant will naturally begin to enter dormancy. You will notice the leaves starting to yellow and drop off. This is a normal reaction and not a cause for alarm. When this happens, you must reduce your watering significantly. During the peak of winter, a dormant Adenium needs almost no water at all. Only give it a small splash if you notice the caudex starting to look wrinkled or feeling slightly soft to the touch. Do not soak it in winter, and keep it out of the rain.
Choosing the Right Soil and Pot for Adenium obesum
The Desert Rose requires a free draining growing medium. A standard potting soil will hold too much moisture and lead to root rot. We recommend our EcoGrit Mix, which is available here. You can also make a mix of 1:1 of our EcoGrit and Super Drainage Mixes to further improve drainage. If your area is very humid, and you find that your soil mixes stay wet too long, then our Super Drainage Mix on its own will be best. You can also add top dressing like our Decorative Kalahari or River Stones.
When it comes to potting, Adeniums actually enjoy being slightly root bound. This often encourages better flowering. If you do need to repot, choose a container that is only a few centimeters wider than the base and root system of the plant. Always ensure your pot has plenty of drainage holes.
Feeding for Flowers
To get the most out of your blooms, you can use a balanced liquid fertilizer during the summer months. Dilute it to half strength and apply it once every four weeks. Avoid fertilizing at all during the winter months when the plant is resting, as the extra nutrients can lead to weak and leggy growth.
A Note on Safety
It is important to remember that the Desert Rose belongs to the Apocynaceae family, the same family as the Oleander. The milky sap found inside the stems and leaves is toxic if ingested and can cause skin irritation for some people. Always wash your hands after pruning or handling cuttings, and keep the plants out of reach of curious pets and small children.
Get your own Adenium obesum