Oleander plants are classic, drought-tolerant, full-sun garden treasures in Southern California. These toxic beauties are simple to care for, produce stunning blooming displays, and are an wonderful addition to any garden.
An oleander dropping its leaves could occur for several reasons. It is easier to identify the reasons behind leaf drop if it occurs with other problems, such as yellowing, damaged foliage, insect indications, or yellowing of the leaves.
Oleander leaf loss can be brought on by cultural factors, pests, illness, and even pesticide spread. You may wonder, “Why are my Oleander leaves turning yellow?”
There are several probable reasons why oleander leaves turn yellow, such as improper watering, poor drainage, a lack of fertilizer, leaf scorching, crowding with other plants, or pest infestation.
In our guide, you can learn more about the issues with your plant that needs immediate attention. By the end, you’ll see the other reasons that cause leaves to turn yellow and drop beside the serious Oleander leaf scorch disease. (Learn How To Test Your Yard For Parvo)
What Causes Oleander Leaves to Turn Yellow
One likely cause of yellowing leaves on oleander is a lack of pruning. Oleanders are fast-growing plants that must be continually pruned to maintain their desired shape and size. If the plant is not pruned regularly, it can lead to too much foliage, crowding out new growth and causing the lower leaves to become yellow and die off.
Pruning also helps the plant get more air, which helps fight off diseases and pests that could cause the leaves to change color. Another potential cause of yellowing oleander leaves is poor soil conditions.
Oleanders prefer slightly acidic soil with a pH between 6.0-7.0 for optimal growth; if the soil falls outside of this range, it can lead to nutrient deficiencies that will manifest as yellowing leaves on the plant.
Inadequate drainage or overly moist soil can create an environment conducive to serious disease in your oleanders. Here, you can find root rot that can cause stunted growth, wilting of foliage, leaf discoloration from nutrient deficiencies, or serious disease spread from roots into stems or foliage.
Cultural Causes of Oleander Leaf Drop
Oleanders leaf drop can be caused by cultural practices that lead to poor root zone health. For example, over-watering or waterlogged soil can cause root rot and hinder the uptake of nutrients from the soil.
This lack of nutrition is then displayed in yellowing leaves and leaf drop. In addition, new growth on oleander may not have established a strong enough root system to take up nutrients, resulting in weak or yellowing leaves that eventually fall off.
Gardeners should avoid over-watering their planted oleanders, allowing the top 2 inches of soil to dry out before watering again. It is beneficial for oleander plants’ health to use potting mix formulated for succulents when planting them in containers. This will help ensure good drainage and allow oxygen into the roots. (Read Do Any Vegetables Grow On Trees)
Poor drainage can cause yellow leaves on an oleander. If the soil is not draining correctly, it can build up excess water in the soil and prevent oxygen from reaching the roots.
This lack of proper aeration will cause the plant’s leaves to yellow rapidly and eventually die off. Poor drainage can also create an environment that is too cold or wet for the oleander to thrive during certain times of the year.
In extreme cases, poor drainage may cause rot or fungal growth on the roots, which could lead to further leaf yellowing and root damage. If your oleander is yellowing rapidly year-round, check your soil for poor drainage and consider altering it if needed.
Pests on Oleander
Nerium Oleander is a popular landscape shrub but is vulnerable
to several pests. Sap-sucking insects like aphids and mealybugs are the most common cause of yellow leaves on oleanders. These insects feed off the plant’s sap, which leaves an unhealthy appearance in its wake.
If left untreated, these pests can weaken or even kill the plant. To prevent such damage from occurring, it’s essential to identify and treat any infestations as soon as possible.
Spraying with horticultural oils or insecticides can help eliminate existing pests and discourage new ones. Also, the oleander must be watered and fertilized correctly to stay healthy and not get attacked by pests.
Lack of Fertilizer
A nitrogen deficiency is present if the young leaves are still green but you have drooping leaves in the older ones. Use a balanced fertilizer to feed any planted Oleander plants. After three to four days, these yellow leaves will turn green.
Oleander plants must be fertilized twice yearly (in spring and fall). They don’t need heavy feeding, so a slow-release fertilizer like 10-10-10 will do.
How Can I Identify Yellowing Caused By Leaf Scorch on Oleander plants?
Oleander Leaf scorch is a common issue with oleander bushes and can cause yellowing of the leaves. The most common causes and signs of leaf scorch are yellowing at the edges and between the veins of the leaves. This happens at the edges, spreads to other parts of the plant, and occurs in late spring and summer.
Brown or black spots may also form on the leaf tips or margins, while veins remain green. Keeping your oleander in well-draining soil and water regularly following dry periods, especially in early spring when new growth begins, is essential to prevent this.
Pruning any deadwood can help prevent the spread and help improve air circulation, reducing risk factors for leaf scorch. (Learn How To Know If Zucchini Is Bad)
Mulching around your oleander will also help ensure adequate moisture levels by decreasing evaporation from soil surfaces, so you don’t need to start watering your oleanders as often. Mulch is also handy as it helps this drought-tolerant plant’s roots last longer with less water.
Sharpshooters, spittlebugs, and leafhoppers can spread Oleander Leaf Scorch, a deadly bacterial illness.
The pests introduce the bacteria (Xylella fastidiosa) into the plant stems when they feed on the plant. The bacteria grow and obstructs the water-conducting channels in the xylem vessels of oleanders where it dwells.
Although leaf scorching can happen anytime, it typically affects Oleander plants in the late spring and summer. Yellow and droopy leaves are the first signs of leaf scorch on an Oleander. The Oleander plant will become brown and burned as the bacteria spreads.
Even most insecticides are useless against this severe disease in oleander plants, making it impossible to treat.
The affected plant must be removed to treat the disease. Some experts advise trimming the infected areas to prevent the disease from spreading. In three to five years, your Oleander plant will eventually perish.
How to Avoid Yellow Leaves on Oleander Plants
There are a few steps to take that can help prevent yellow leaves on oleander plants.
- First, inspect the plant for sap-sucking insects such as aphids or whiteflies. These pests can cause yellowing of the leaves because of their feeding habits. If found, use insecticidal soap to get rid of them.
- Second, ensure the plant gets enough water and nutrients and is not over or under-watered. To water Oleander plants, use a trickle irrigation system. Watering more in the summer so the roots can be nourished is more important.
- Brown or yellow spots on the leaves can be caused by overwatering or underwatering, so ensure your oleander gets just the right amount of water and fertilizer for its needs.
- Finally, prune off dead branches or brown leaves to keep your oleander healthy and vibrant. Pruning also helps increase air circulation around the plant, which helps deter insect infestations in the future and stimulate young growth.
Your oleander’s older growth and shadowing may cause most of its issues. Instead of cutting off the tops of the plants, prune them differently by taking one or two of the largest stems from the base of each plant. (Read White Spot On Orchid Leaves – What To Do)
Doing this in February, just before fresh growth, is recommended. You’ll notice new growth coming from the base, cuts, and areas that receive light. You will repeat this procedure to promote new succulent growth from the base every year, every two years, or every three years.
Hedging, or continually pruning your plants, will create large old wood at the base of the plant without any leaves. The leaves fall off the wood as it ages. You must continually renew young growth from the bottom if you wish to have leaves.