Oleander, or nerium, is a shrub or small tree grown worldwide in temperate or subtropical climates. This ornamental and landscaping plant has colorful flowers that are pink, red, yellow or white, and are extremely toxic to humans and animals. It is the sole species classified in the genus Nerium. It grows from seven to 20 feet, is easy to care for and can tolerate hot weather, but this plant is also prone to issues that cause yellowing leaves.
Oleander Leaves Turning Yellow: What Are The Reasons?
1. Improper watering
Oleander leaves turning yellow could be due to improper watering of the plants. Plants have certain watering needs depending on light, soil, humidity and temperature.
Oleanders are drought resistant, but they do prefer to be watered consistently, especially during dry periods. These plants also cannot tolerate overwatering, and if they are overwatered, their leaves will begin to turn yellow.
To remedy overwatering, do not plant oleander in soil that does not drain easily. Try to change the watering schedule and hold off watering for a while.
Underwatering, meanwhile, is a minor issue but should also be avoided. The root tips tend to die in dry soil and nutrients become depleted. To fix this problem, increase the water intake of your plants by watering more frequently.
2. Poor drainage
You may be watering your plants right, but wondering why the leaves are still turning yellow. The culprit could be inadequate or poor drainage. The pots you are using for your oleander plants may not have proper drainage holes, or the soil mix may not be the right kind.
To fix the problem, use a balanced soil mix for your oleander plants. The soil should be able to retain moisture while draining excess water. These plants can adapt to various soil types, but do not use a porous soil mixture as it cannot hold sufficient moisture for the roots. Also, do not use compacted soil as this retains more water than required by the plant.
If rainwater stands in the soil it could cut off the oxygen supply for the roots. This can stress the plants and they may develop yellow leaves.
3. Lack of fertilizer
Fertilizing your oleander plants is essential for them to absorb vital nutrients like nitrogen. If the plants are not fertilized, the older leaves tend to turn yellow. By feeding your plants with a balanced fertilizer the yellowing leaves will change to green in a matter of days. Oleander plants should be fertilized bi-annually, but they do not require heavy feeding.
4. Leaf scorching
Oleander leaves turning yellow could also be due to leaf scorching, a fatal bacterial disease spread by leafhoppers, sharpshooters and spittlebugs. These pests feed on oleander plants and introduce the bacteria, Xylella fastidiosa, to the plant stems. The bacteria thrive in the plant’s xylem vessels and block these water-conducting channels.
Leaf scorch disease is characterized by yellow, droopy leaves and, as the bacteria grow, the plants will appear scorched and brown. To fix the problem, you have to remove or dispose of the infected plants. Most insecticides cannot eradicate this disease, so disposal of the plant is the only solution.
5. Crowding with other plants
Oleander plants need plenty of space to grow because of their extensive root system. When they are placed too close together with other plants, it can harm their roots. Planting them in crowded areas in your garden could lead to a sickly and yellow appearance. To fix the issue, you need to replant them and make sure there is adequate spacing between the plants.
6. Pest infestation
Oleander plants are vulnerable to pests that suck their sap, such as scale insects and aphids. Scales have whitish-brown, flat, oval bodies, while aphids are usually found on the undersides of leaves. As they feed on the plants, the plants become weak resulting in yellow leaves. To fix the issue, use neem oil or isopropyl rubbing alcohol and wipe or spray on the affected plant parts.
Helpful Tips to Prevent Yellow Leaves on Oleander Plants:
- Use a trickle irrigation system, because overhead watering will soak the leaves.
- Check the soil and if it retains water, increase the drainage or reduce the irrigation.
- If you notice the area around the leaf’s central vein yellowing, your plant is stressed due to lack of water.
- Water your plants regularly, but with little water, as watering them heavily after a dry spell could trigger yellowing leaves.
Conclusion
Oleander plants are lovely ornamental plants with colorful flowers. Like most plants, they also suffer from certain conditions that cause their leaves to turn yellow. This could be due to pest infestation, overcrowding, improper watering, poor drainage or bacterial diseases.
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