Oleander plants are large shrubs that grow 20 – 25 ft. (6 – 7.6 m) high. These ornamental plants can produce clusters of colorful flowers (pink, yellow, red, and white) in the summer season. These Mediterranean plants are famous for their poisonous qualities and rose-like blooms.
They are a wonderful addition to any outdoor garden because of the long blooming season. Oleander plants are easy to care for, but they can have issues like yellow leaves with improper care.
What Causes Oleander Leaves to Turn Yellow?
The most common reason for yellow leaves on Oleanders is overwatering, and the worst case is the Oleander Leaf Scorch. You should not over or underwater your Oleander plant. Yellow leaves on these plants can be easily prevented with a proper soil mixture, watering schedule, fertilization, and plant hygiene. However, if yellow leaves are caused by leaf scorch, the only solution is to get rid of the plant.
Caring for an Oleander Plant
Even a single Oleander plant can add a colorful accent to any garden, but for that, you need to provide necessary plant care. These are not very demanding plants as long as you get the basics right.
It is recommended to grow Oleander plants in a well-draining, compost-enriched soil mixture and full sunlight exposure. If your plant is growing under bright sunlight but not receiving enough water, it will dehydrate and become stressed.
The ideal time to water an Oleander plant is when the leaves are grey with a matt finish. You can water them every three days provided the topsoil (2-3 inches) is dry.
It should be watered slowly but deeply. If you only wet the topsoil surface, the salts can accumulate and damage your plant.
Causes of Yellow Leaves on Oleander Plants
The yellowing of leaves on Oleander indicates a variety of issues that need immediate attention.
Knowing and understanding your plant needs is important to protect them against yellowing. Below are the most common causes of yellow leaves on Oleander plants.
Watering plays an important role in the well-being of plants. Each plant has its own watering needs depending on soil, light, temperature, and humidity. Improper watering is the most common reason for the yellowing of the leaves.
The Oleander plant is considered sturdy and drought tolerant, but it enjoys plenty of watering during dry periods. Most gardeners end up overwatering this plant after the soil has dried out.
Oleander plants cannot withstand overwatering. Therefore, never plant it in soil that does not drain freely.
Yellow leaves caused by overwatering Oleander plants can be easily fixed by changing the watering schedule.
Underwatering should also be avoided. Otherwise, the root tips will die in dry soil, and nutrient levels will deplete, causing yellow leaves. These root tips will revive once you improve the water intake.
Sometimes you are watering your plant well, but it has inadequate drainage. Either the pot does not have proper drainage holes or the soil mix is not right.
You have to use a balanced soil mixture for Oleander plants; it should retain necessary moisture and drain the excess water. Oleander plants can adapt to several types of soils but
- Do not use a very porous soil mixture because it cannot hold proper moisture for the roots.
- Do not use a compacted soil mixture because it will retain more water than required by the plant.
In outdoor gardens, if the rainwater remains standing in the soil, it will terminate the oxygen supply to the roots. This stresses the plant, and soon it starts developing yellow leaves.
Lack of Fertilizer
If the new leaves are still green, but the old ones are yellowing, there is a lack of nitrogen. You should feed your plant with a balanced fertilizer. These yellow leaves will start greening in 3 to 4 days.
Oleander plants should be generally fertilized twice a year (in spring and fall). They do not require heavy feeding; a slow-release 10-10-10 fertilizer is enough.
Another main reason for the yellowing of Oleander leaves is leaf scorching. If you are maintaining a good watering schedule, inspect your Oleander plant for leaf scorch. Every Oleander plant variety is susceptible to this disease.
Leaf scorching was first observed when a large number of Oleander bushes started yellowing in Southern California (in 1990).
Oleander Leaf Scorch is a fatal bacterial disease spread by sharpshooters, spittlebugs, or leafhoppers. These pests feed on the plant and introduce the bacteria (Xylella fastidiosa) in the plant stems.
The bacteria lives in xylem vessels where it multiplies and blocks the water-conducting channels.
Leaf scorching can occur in any season, but most growers have experienced it on Oleander plants in late spring and summer.
The initial symptom of an Oleander leaf scorch is yellow and droopy leaves. As the bacteria continues growing, the Oleander plant will appear brown and scorched.
Oleander plants cannot be cured of this deadly disease even most insecticides are ineffective against leaf scorch.
The only solution to this disease is to remove the infected plant. Some experts suggest pruning the diseased parts, but that will only slow down the spread of the disease. Your Oleander plant will eventually die in 3-5 years.
If you plant it in a crowded region, the green leaves of this toxic beauty will have a sickly, yellow appearance. This happens when it is planted very close to other plants in an outdoor garden.
This plant has an extensive root system that requires plenty of space to grow. Improper spacing between plants can impact the roots. As a result, the Oleander leaves turn yellow.
Oleander plants can also have yellow leaves due to pest infestation. These plants are vulnerable to sap-sucking pests like scale insects and aphids.
Look for Oleander aphids on the undersides of the leaves on your plant. Oleander scales are sap-sucking insects that have whitish-brown flat, oval bodies.
These sucking insects will feed on plant nutrients, which leads to yellow leaves. Treat the pests with neem oil or isopropyl alcohol.
Useful Tips to Avoid Yellow Leaves on Oleander Plants
- Check the soil regularly. If it remains too wet, you should reduce irrigation or increase the drainage.
- To water outdoor Oleander plants, use a trickle irrigation system because overhead watering will wet the leaves unnecessarily.
- If the area around the central vein is yellowing, your plant is under stress due to a lack of water.
- Watering your Oleander plant heavily after a dry spell can also trigger yellow leaves. I would suggest watering regularly but with little water.
Frequently Asked Questions About Yello Oleander Leaves
How can I identify yellowing caused by leaf scorch on Oleander plants?
When your Oleander is infected with leaf scorch, the yellowing of leaves begins at the tip of the leaf and spreads inwards. The infected plant should be immediately destroyed because there is no cure for this disease.
Can temperature at soil level cause yellow leaves on Oleander plants?
This is a rare case, but if the base of the plant at the soil level is too hot, the leaves will turn yellow due to temperature damage. This happens because the roots cannot function properly in this condition. You should add mulch like grass clippings, pine needles, or leaves.
When should I water my Oleander to avoid yellow leaves?
Many growers misjudge the drought tolerance of Oleander. This plant can handle drought periods, but it does not mean it has low water needs. This plant should not be watered every day, but you can water it deeply every week.
Marcel runs the place around here. He has a deep passion for houseplants & gardening and is constantly on the lookout for yet another special plant to add to his arsenal of houseplants, succulents & cacti.
Marcel is also the founder of Iseli International Commerce, a sole proprietorship company that publishes a variety of websites and online magazines.