Adenium's Caudex Is Turning Yellow

Root Rot

• Adeniums can withstand severe drought but cannot stand excessive watering. The most common disease in this plant is root rot, which is caused by the roots becoming too moist. If your plant is affected by root rot, the leaves will all begin to yellow and fall off in a matter of days. By the time this has begun happening, it is already too late for your plant. If the Adenium plant is large enough, you may just lose a portion of the root system and it might bounce back. If this appears to be the problem, stop watering immediately and let the plant rest.

Nitrogen Deficiency

• Nitrogen is the most important nutrient for the healthy growth of most plants. The Adenium caudex requires more nitrogen and other essential nutrients than most other plants. Nitrogen deficiency can be recognized by yellowing and dropping of lower leaves of the plant and generally small and unhealthy new growth of leaves and flowers. To combat this, use a complete fertilizer with equal parts nitrogen, phosphate and potassium as the Adenium requires these other micronutrients as well. Fertilize at least twice a year, just before winter and at the onset of spring. Use ammonia nitrate fertilizer as opposed to ammoniacal nitrogen-based fertilizer as the latter can encourage leggy and sparse upright growth.

Micronutrient Deficiency

• In addition to nitrogen, phosphorous and potassium, plants also depend on thirteen micronutrients for healthy growth. The Adenium caudex needs these nutrients as much as any other, but is especially affected by zinc and iron deficiency. A lack of either of these nutrients will cause chlorosis in the plant leaves, meaning the leaves are no longer capable of producing chlorophyll and therefore cannot photosynthesize. This can be witnessed as a loss of green pigment to the plant leaves. Many fertilizers are loaded with micronutrients as well as the three -- nitrogen, phosphorous and potassium. Purchase a fertilizer that contains zinc and iron for your Adenium. If not, zinc sulfate and iron phosphate are available at most garden centers and can be used to amend the soil accordingly.

Stem Rot

• There are many pathogens that can enter the Adenium caudex through the leaf system, usually as a result of interaction with insects feeding off the plant. Most of these pathogens will first be recognizable by subtle yellowing of leaves in a concentrated area, followed by rotting of the stems attached to the leaves. The Adenium caudex will often quarantine and lose infected stems on its own once they have died off; to be certain, cut stems off below the point of infection.

Blight

• Blight is a disease that affects species across the spectrum of the plant kingdom, including the Adenium. It is recognizable by the appearance of yellow leaves with small black spots intermittently throughout. Systemic fungicides that are added to the soil are available at most garden centers to combat blight in the Adenium's caudex.