Although the oleander is native to the Mediterranean region and, as a Mediterranean plant, is quite used to dry seasons, the shrub is not a typical Mediterranean plant in one respect: it needs a lot of water, especially during the summer months, and should also be watered regularly in the winter quarters. It depends on the right amount, because if you water the oleander too much or too little, it will get dry leaves.
If the oleander gets dry leaves, it should be watered more
Oleander needs a lot of water - even in winter
In its natural habitat you will find oleanders near rivers and streams, which often dry up in summer. However, the shrub can develop immensely long roots so that it can help itself from the groundwater during the dry months - the hard leaves do not store any water. Of course, this is not possible with oleanders cultivated in pots, which is why they have to be watered regularly: on hot summer days several times a day, during the winter in the cold winter quarters about once a month. If possible, use stagnant tap water for this, not rainwater - the shrub needs lime.
Root damage can also be the cause
However, brown, dry leaves do not necessarily have to be an indication of a lack of water, but can also be due to too much water. Although this cause is less common with oleanders, since the plant usually has no problem with waterlogging (at least not in the summer months), it can occur due to the lower root activity, especially due to too frequent watering in the winter quarters. The roots are damaged in such a way that they turn brown and rot - and of course the above-ground parts of the plant can no longer adequately supply water and nutrients: dry leaves and shoots are the result.
Dry leaves on the oleander must be removed
In this case you have to pot up the affected oleander, cut away all brown or rotten roots and replant the plant in a new container with fresh substrate. Remember that when pruning the roots, the parts above the ground must also be pruned back - in this case all dry leaves and shoots.
tips
In addition to a lack of water, frost damage that occurs during the winter is a common cause of dry leaves on oleanders. The Mediterranean plant is not hardy in our latitudes - even if short-term temperatures of up to minus five degrees Celsius are usually not a problem. These dry leaves should also be removed as they will not turn green again.