The most likely causes of Oleander leaves turning Yellow are improper watering, poor drainage, or disease. By far the most common cause of yellowing is overwatering or improper drainage. A disease called ‘leaf scorch’ is also common among oleanders and causes yellow leaves. Alternatively, it may be pests that are the problem.
I tend to notice a lot of oleanders suffer from over-watering. It’s easy to do, and the plant can’t stand it. So my guess is that this is the cause of those yellow leaves.
But, if you are sure you are maintaining a proper watering schedule, I’ve got a few other suggestions. Unfortunately, some are better news than others. Let’s take a look at them in more detail.
A tall shrub with a bright bloom of rose-colored (or, occasionally, white or yellow) flowers, oleanders are a great way to add an accent of color to your garden. This plant originates from the Mediterranean and is widely grown in warmer countries.
Oleanders are known for their beauty, but they are also known for their poison. They actually belong to the dogwood family, and just like this famous poisonous plant, they contain a milky toxic sap.
Be aware that all parts of the plant are poisonous to eat and this sap can cause skin irritation. It’s a good idea to wear gloves when handling the plant.
It’s a testament to their beauty that, despite their poisonous nature, they are a remarkably popular ornamental plant grown across the US.
They are typically easy to care for once you have the right balance of water, nutrients, and light. However, if you notice it yellowing, these are the common causes.
Once a week, water deeply around the oleander if it hasn’t been raining. The topsoil, the top 2-3 inches, should be completely dry before adding the next.
Oleanders can’t stand overwatering and it will quickly turn the plant yellow. But once you have the plant on a proper watering schedule, this should correct itself quickly.
While striving not to overwater, it’s important to not end up underwatering your oleander plant. Although this makes it seem an impossible balancing act, you will find it easy once you are on the right schedule.
If the oleander is under very bright sunlight, you will need to water more frequently as the soil will dry out much faster.
Even if you are not overwatering your oleander, poor drainage can leave it sitting in water that you cannot see beneath the topsoil, especially if it’s been raining heavily, and this can damage the plant. Don’t use porous or compact soil for oleander planting.
If you believe your oleander has improper drainage, you’ll need to move the plant. Shovel around the plant and lift the root ball from the soil. If any roots have been damaged, trim these away.
Plant the shrub in an equal-sized hole in the new location with well-draining soil. Add water when the hole is half-full to settle the soil, and use mulch over the whole root area.
As the name suggests, this disease gives the oleander’s leaves a scorched appearance and slowly spreads from leaf to leaf eventually causing them to droop and turn brown. If that describes your yellowing leaves it may, unfortunately, be what's affecting your plant.
This disease has been found in oleanders for the last 25 years, most predominantly in California. Unfortunately, no treatment has been found effective against this disease.
The plant will not die right away, but the yellowing will spread from leaf to leaf and the plant will die in time.
You can trim the leaves to slow the disease's spread and improve the appearance of the plant, but this will not fully stop the spread of the bacteria.
However, if you have healthy and uninfected oleander plants nearby, remove and destroy the plant to save the other bushes from infection.
Oleander plants can be prey to a few hungry pests, but a well-cared-for plant should be able to withstand the attack. Small aphids and whiteflies feed on oleanders, sapping nutrients and turning them yellow.
Check the underside of the leaves for these small creatures to find the possible cause of the plant’s discoloration. If you spot them, don’t worry as they are easy to remove.
A short, sharp jet of water will do most of the work. After this, apply horticultural oil to keep the pests at bay.
The most damaging is the oleander caterpillar, which feeds in groups and leaves large unsightly holes. However, they are large and can be simply picked off and dropped into a bucket of soapy water.
For a more severe case, an application of bacillus thuringiensis should do the trick.
Frequently Asked Questions
Want to know more about oleanders? Here are some other frequently asked questions about oleanders asked and answered.
Q: How long do oleander plants live?
A: Well-cared-for oleanders typically live for 20 years.
Q: How can I make my oleander grow faster?
A: Established oleanders need little to no fertilizing, but feeding a young plant with 10-10-10 granular fertilizer can increase its growth rate and help it to mature faster.
Q: Can you grow oleander in a pot?
A: Yes, oleanders can grow indoors if kept in a bright spot away from central heating.
Oleander Leaves Turning Yellow – Conclusion
So, that covers the main reasons you might be finding yellow leaves in your oleander bush. My hope is that it is simply overwatering.
These, and pest problems, are easy to correct and your plant should be in good health in no time. If leaf scorch has infected your plant, this is more unfortunate news.
Pruning away the infected parts, though, can sometimes keep the plant alive another five years!
Check out our other plant health guides that look at if your Rose of Sharon or Nasturtium leaves are turning yellow.