Q: When can I prune oleanders? They are about 8 feet tall and I’d like to cut them back to about 5 feet.
A: the best time to prune oleanders is late winter just before new growth occurs (February-March). Oleanders flower on current season’s growth. So if you prune at the above time, you’ll still get flowers. However, if you severely prune the plants (taking out 1/3 or more of the above-ground portion), they may not bloom very much for several years. Pruning severely causes a plant to put all of its energy into recovering the lost growth at the expense of producing flowers. This is particularly true if you severely prune and then fertilize with a high-nitrogen fertilizer including fertilizing the grass that is in close proximity to the oleanders. But sometimes the need to severely reduce their size overrides the desire for flowers.
When a plant becomes too large for its location, the problem really goes back to planting the wrong plant in the wrong place. Even though we may not know the mature size of a plant when we plant it, the plant is only doing what it is supposed to do. Oleanders get much taller over time than many people realize.