The caudex of an Adenium, often called the trunk or belly, is a specialized stem structure known as a caudiciform. From a botanical perspective, it is a water-storage organ, a succulent stem that has evolved to swell and retain moisture to help the plant survive extended periods of drought in its native arid environments. A healthy caudex is firm and turgid due to the water pressure (turgor pressure) within its parenchyma cells. These cells are thin-walled and designed to hold large amounts of water. When this structure becomes soft and squishy, it indicates a failure in this water-storage system, almost always pointing to cellular damage or degradation.
The most common reason for a squishy caudex is root rot, which is a physiological disease caused by environmental conditions. Adenium roots require a cycle of thorough watering followed by a period where the soil dries out completely. Constantly wet or poorly draining soil creates an anaerobic (oxygen-deprived) environment. In this state, opportunistic soil-borne fungi, such as those from the Pythium or Phytophthora genera, attack the roots. These pathogens infect the root system, destroying the vascular tissues—the xylem and phloem—that are responsible for transporting water and nutrients. As the roots rot and die, they can no longer absorb water. Consequently, the plant begins to consume the water stored in the caudex, causing it to shrink and soften from the bottom up.
Conversely, a squishy caudex can also result from extreme and prolonged dehydration. While the plant is designed to handle drought, there is a critical limit. If the soil becomes a completely dry, hard brick and the plant exhausts its stored water reserves, the parenchyma cells in the caudex will lose their turgor pressure and collapse. This cellular collapse leads to a wrinkled, deflated, and soft caudex. Unlike the mushiness of rot, this often feels more leathery or spongy. The plant's metabolism slows to a near halt, and without intervention, it will not have the water resources needed to regenerate new roots or leaves.
Upon discovering a soft caudex, immediate action is required. The first step is to unpot the plant carefully. Gently remove all the soil to expose the root system and the base of the caudex. Wash the roots under running water to get a clear view of the damage. Using a sterilized, sharp knife, proceed to cut away all soft, mushy, brown, or blackened roots and tissue. Healthy roots are firm and may have a whitish or tan color. You must cut until you reach only firm, healthy tissue, even if this means removing a significant portion of the rootball or even carving out soft spots from the caudex itself.
After the surgery, it is crucial to treat the cut surfaces with a fungicide powder or a solution (e.g., one containing thiophanate-methyl or copper-based compounds) to prevent further fungal infection. Then, the plant must be placed in a shaded, well-ventilated area to allow the wounds to callus over completely. This process can take from a few days to over a week. The callus is a layer of dried tissue that acts as a natural barrier against pathogens and moisture loss.
Once fully callused, the plant should be repotted into a fresh, fast-draining succulent or cactus mix. You can improve a standard mix by adding plenty of perlite, pumice, or coarse sand. The pot must have ample drainage holes. Do not water the plant immediately after repotting. Wait for 7 to 10 days to allow any minor root disturbances to heal, then give it a light watering. Place the plant in bright, indirect light and resume a careful watering regimen only when the soil is completely dry. The goal is to encourage the growth of new, healthy roots without restarting the cycle of rot. Recovery is a slow process, and it may take weeks or even months before the caudex regains its firmness and the plant shows signs of new growth.
