In Italy and Spain, the sometimes very large bushes with their tireless flowers can be seen everywhere: even further north, for example in Ticino, many gardeners enjoy the magnificent shrubs in their garden. But even if you have discovered wonderful oleanders in the gardens in Bologna or on Lake Lugano: Planting them out is not a good idea in Germany due to their very low frost hardiness.
Oleander can only tolerate a little frost
Oleander is only winter-hardy down to around minus five degrees Celsius and can only tolerate these low frosts for a very short time. Lower or even permanent temperatures below zero, as is often the case in many regions of Germany, are usually fatal for the Mediterranean shrub. The plant does not die immediately if its above-ground shoots freeze away: In this case, simply cut the frozen bush back to just above the ground and it will sprout again. However, ground frost is fatal as the roots are affected and die. Once the oleander roots have been frozen, the plant can no longer be saved.
Planted oleander is more robust - but only with a plant pot
For this reason, planted oleanders - whose roots are in the protective soil - are significantly more robust than potted oleanders, whose roots freeze more quickly due to the planter. In mild winters, you can overwinter the shrub by burying it in a suitable spot in the garden (if possible in spring). However, the plant pot must not be removed so that the oleander can be quickly dug up again when frost threatens and put into a safe winter quarters.
Overwintering oleander properly
Oleanders overwinter best in a frost-free, but cool and bright room at temperatures of around five degrees Celsius. For example, unheated greenhouses or winter gardens, stairwells, attics or basements are ideal. Even if the location is dark, you can place the shrub there, but then the temperatures should not rise above two degrees Celsius. Don't forget to water the oleander about once a week, but you should stop fertilizing in late summer.
Tip
As long as the temperatures are still mild, you can overwinter your oleander outside. In this case, it is best to wrap it carefully with bubble wrap (€39.00 on Amazon) and/or gardening fleece and ensure that it is protected from wind and rain as much as possible.