Oleander gets brown and dry leaves: this is how you save it

oleander (Nerium Oleander) is one of the most popular container plants with its beautiful flowers. The plant, which is also called rose laurel, is evergreen and impresses with leathery, dark green leaves even outside of the flowering period. Depending on the variety, these can reach a size of up to 24 centimeters. However, if the leaves suddenly turn brown, it is necessary to investigate the cause. Diseases or care errors can show up through discoloration or dry leaves.

Leaves and flowers

The leaves of a healthy oleander plant appear a dark, rich green. The plant, which comes from the Mediterranean region, is leafy all year round. The leaves only die off when the temperature is very low. Therefore, a cool, dark room with a temperature of 5 to 10 degrees Celsius is recommended for wintering.
The flowers of the rose laurel appear in white, yellow, pink or purple, depending on the variety. Wild oleander has purple flowers.

Attention: Oleander belongs to the dog poison family. All parts of the plant are strong poisonous!

Causes of leaf discoloration

If the foliage of the oleander becomes discolored or blotchy, it is mostly due to care errors, excessive sunlight or illnesses.

• Lack of moisture
• Overfertilization
• too strong sunlight
• Oleander cancer infestation
• Dry rot / Ascochyta

1. Lack of moisture

Dry leaves are a sign of a lack of moisture. Because the oleander must be sufficiently watered for a beautiful bloom and healthy foliage. Avoid drought stress, it is detrimental to the development of the plant. If you notice dry leaves, then appropriate measures can be taken to save the plant. Immerse the oleander in water until the root ball is soaked and no more air bubbles rise. Make sure that the substrate is always moist enough.

tip: Never water the rose laurel in full sun!

2. Overfertilization

An excessive fertilization can lead to brown discoloration of the leaves. If you recognize brown spots and suspect a fertilization error, you can remedy a container plant with strong rinsing. Water the container plant and make sure that the water can drain well. It is best to remove the saucer or the planter.

Refrain from fertilizing in the following weeks. Do not fertilize again until the plant has recovered well.

tip: “A lot helps a lot”, that definitely does not apply to fertilizing! The correct dosage is particularly important for potted plants. Due to the limited amount of substrate, over-fertilization cannot be compensated for and quickly leads to damage to the plant.

3. Too much sun after hibernation

oleander overwintered good in the cold cellar. If you free him from winter quarters in spring, you should carefully examine the plant, because some diseases tend to develop in winter. If you put the plant outdoors, it should also be at night no frost to be feared. Above all, you should not place the plant in the blazing sun. Strong sunlight can discolour the leaves. Choose a shady place where the container plant can slowly get used to the new location.

4. Oleander cancer (Pseudomonas)

A bacterial disease called oleander cancer is a common cause of brown spots on oleander leaves. The trigger for this is the bacterium Pseudomonas syringae pv. savastanoi. The disease does not have to cause the plant to die if you act in a timely manner. Symptoms for oleander cancer can include discoloration, crippling and deformation of inflorescences, buds and shoots. The manifestations are different. First, changes appear in the most sensitive parts of the plant, the buds and flowers. These can turn dark, do not bloom and fall off. After that, brown spots appear on the leaves. These areas become dry and burst.

Actions in Oleander Cancer

So far, no drugs against oleander cancer are available. Therefore, to fight the disease, only a radical one will help Cut back. Cut all clearly visible infected shoots back to the healthy wood. Shoots that show only slight signs of oleander cancer can be left standing; they usually recover well. Make absolutely sure that sterile cutting tool to use.
Watch out, too Aphids transport the Pseudomonas bacteria. Eliminate this with a solution of 1 liter of water, 2 tablespoons of soft soap and a little alcohol. Spray the solution on the plant every two to three days until there are no more aphids.

tip: Parts of plants affected by oleander cancer are highly infectious. To protect other plants, you should therefore never compost the cut parts of the plant. Burn the plant parts or dispose of them in the residual waste bin.

5. Dry rot (Ascochyta)

Ascochyta is a threat to oleander plants. This dry rot shows up on the inflorescences mainly in winter. They dry up and die. The dry spots continue to spread. When the dry rot has gotten to the trunk of the oleander, the entire plant will die. Ascochyta is a fungal disease. The Ascochyta mushrooms form spores that penetrate the oleander tissue and continue to spread. Summers with a lot of rain represent a major risk of illness. The ascochyta mushrooms spread through the rain and watering.

Measures to be taken in the event of an Ascochyta infestation

If you notice an ascochyta infestation on your plant due to deformations and dry spots, you should act quickly. Because you can still save your oleander! However, all parts of the plant above a visibly affected shoot can no longer be preserved. Therefore cut off all affected parts of the plant and all shoots above.
Preventive spraying, especially in autumn before the start of hibernation, can protect against an infestation with Ascochyta.

tip: Injured tissue is a gateway for ascochyta fungi and other oleander diseases. Therefore, seal all cut surfaces after a cut back. No pruning should be done in autumn.