I have a garden in Southern Switzerland with three mature oleanders already planted. I want to infill with new plants to make a hedge. Can I plant now or should I wait until spring?
Fall is a good time to plant as well as spring. Make sure you water adequately to ensure the roots become established before winter.
Mulching the new plantings will help with moisture retention. 2 to 3 inches of hardwood mulch.
Here is a link with growing information.