The enchantingly beautiful oleander with long, dark green leaves and delicate flowers is a real feast for the eyes. No wonder, then, that this shrub is often cultivated as an ornamental plant. Since the quite demanding plant is preferably kept in tubs due to its lack of winter hardiness, brown spots on the leaves - often due to care errors - are not uncommon. But they can also be a symptom of the widespread oleander canker.
Only cutting away helps with oleander canker
Brown leaf spots can be an indication of oleander canker
Oleander canker is caused by Pseudomonas bacteria that thrive in the sap of the bush. Since in principle almost all oleanders are infected, an outbreak of the disease is not that unusual. A first sign of an outbreak is stunted flowers and buds that either don't open at all or even turn black and then burst open. As the process progresses, brown spots appear on the leaves, which also break open. On the other hand, the shoots show the typical cancerous growths.
Only scissors help against oleander canker
There is no cure for oleander canker except for one thing: sharp scissors. Generously cut away infected parts of the plant. In the case of a severe infestation, you can also place the affected oleander on the stick. That means you cut it down to just above the ground. As a result, the plant will sprout again healthy, but you have to do without flowering for at least a year.
Other causes of brown spots
However, brown leaf spots do not always have to be an indication of oleander canker, other causes can also be considered. A so-called leaf edge necrosis - this is characterized by a brown leaf edge and brown spots - is an indication of over-fertilization. This makes for a rather unsightly appearance of the plant, but is otherwise harmless. In addition, incorrect hibernation - especially if it is too dry and / or too warm - can lead to brown discoloration of the leaves. Make sure you water the oleander sufficiently even in winter and overwinter it at around 5 °C and as brightly as possible.
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On the other hand, if the leaves of the oleander tend to turn yellow, a lack of nutrients and/or water is the most likely cause.