Desert Rose plants (Adenium obesum) can develop yellow leaves for several reasons. Some as simple and benign as a change of seasons.
Desert Rose plants’ leaves may turn yellow in the fall. Poor conditions can also cause yellowing leaves.
For example:
- Too much water
- Too little water
- Too little light
- Fungal infection
- Pest infestation
… All may cause yellowing leaves.
Leaves Yellow On Adeniums Due To Seasonal Change
Desert Rose is a tropical, evergreen plant. It is only winter hardy in USDA hardiness zones 10 through 12. For this reason, it is usually kept as a houseplant.
When grown outdoors or in a very cool setting indoors, the plants’ leaves may turn yellow with leaf drop in autumn. This signals a transition into a dormant state.
You choose whether to overwinter the Desert Rose as an active houseplant or allow it to go into dormancy.
If the plant is in a small pot bring it in before the weather turns cold to prevent yellowing and dropping leaves.
Choose to keep the plant in dormancy through the winter. Reduce watering and keep the soil dry for a period of 3 to 4 months (typically between October and February).
Keep plants in a cool (55° to 60° degrees Fahrenheit) low light setting during the dormant season. Move it to a brighter, warmer setting in the springtime and give it a feeding. It will begin to produce new leaves shortly.
Over Watering
True to its name, Desert Rose is a plant that does best in an arid environment. During the growing season, use the soak-and-dry method of watering.
Water thoroughly and then wait until the top 2″ inches of soil are almost completely dry. Then provide another thorough watering.
During the plants’ dormant season, sharply reduce watering. Move large, outdoor container plants to a location away from any natural rain. The plants should glean enough moisture from the air to do well during the dormant period.
Water smaller indoor plants no more often than once a month during the dormant period.
Related: Tips on Desert Rose Watering
Under Watering
During the plants’ growing season, provide a thorough watering whenever needed. If your Desert Rose stays dry for an extended period, the result is yellowing starts followed by dropping leaves.
Wrong Soil
Even if you reduce watering, a Desert Rose can suffer from too much water if not planted in a good potting soil.
These desert plants do well with a sharply draining, gritty, sandy soil. Use a potting mixture recommended for cactus and succulents and a pot with drainage holes.
Related: Best Potting Mix For Desert Rose
Nutrient Deficiencies
Although Desert Rose is not a heavy feeder, it does need some nutrition. During the growing season, fertilize weakly – weekly.
Give the plant a half-strength dose of balanced 20 – 20 – 20 liquid fertilizer once a week. Stop fertilizing during the winter months.
Related: Fertilizer for Desert Rose
Low Light
All plants need sunlight to produce chlorophyll and grow green leaves. Keep your Desert Rose plant in a low light setting during the dormant period. Move the plants to a bright sunny spot during the growing period.
Remember this plant needs a hot, dry setting to survive, thrive, and bloom.
Fungus
Overwatering, overcrowding, and too little light can result in a fungal infection:
- Root Rot
- Stem Rot
- Leaf Rot
Brown, rusty spots on the leaves. Dark, soft spots on the trunk. A general listlessness along with yellowing, falling leaves often say rot.
If you suspect a fungal infection, isolate the plant from other plants.
Give the Desert Rose:
- Good lighting
- Ample spacing
- Air circulation
- Withhold water until the soil is completely dry
Prune away leaves and stems that exhibit fungal infection symptoms.
To prevent spreading fungus:
- Use a sterilized cutting tool
- Wipe the blade with isopropyl alcohol between cuts.
While the plant is recuperating, spray it weekly with a fungicidal mixture, such as a Neem oil spray.
Mix a couple of tablespoons of neem oil to a gallon of water for an effective, natural treatment.
If the plant needs repotting use clean, new soil along with a new, clean (or sterilized) container.
When repotting, examine the roots. Trim away any soft, mushy roots with a sterilized, sharp cutting tool.
Pests
The same poor conditions that result in fungal infection cause Desert Rose to become subject to pest infestation.
Common houseplant pests such as:
- Mealybugs
- Aphids
- Spider mites
… take up residence on weakened plants.
Related: Getting Rid Of Desert Rose Aphids | Adenium Pests and Diseases
Deal with these insects as you would treating fungal infections.
Spray a Neem oil mixture on the pests. Or mix up a solution of insecticidal soap at a rate of 5 tablespoons to 1 gallon of water. Spray every other week.
Leaves turning yellow on Desert Roses is not the end of the world. Review the steps to determine your next action.