Q. I have large oleanders that need to be pruned. When should they be pruned and how drastically can they be cut back?
A. The best time to prune oleanders is during 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 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. 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 goes back to planting the wrong plant in the wrong place. It’s best to know the plant’s mature size before we plant.
Q. I have a large hibiscus that needs to be trimmed. How low should it be pruned? I hate to just cut the stalks 5 feet off the ground – it would look like an unfinished wicker basket sitting there.
Next to it is an azalea that is similarly out of control. Should I wait until after it has bloomed to cut it?
A. The best time to prune the hibiscus would be just before or just after spring growth. This would be late February to mid-March. Hibiscus responds well to severe pruning. If needed, you could prune it back to about a foot from the ground. But you do not have to go that low. Just remember that pruning stimulates new growth and most of the new growth will occur only several inches below the pruning cut(s). So knowing that the new growth will occur just below where you make cuts will allow you to decide where the pruning cuts need to be made to result in a more natural looking plant. Eventually, the plant will regain its height and spread but it can be pruned again to reduce its size.
Azaleas bloom on last year’s growth. They already have their flower buds tucked away at the ends of each shoot now. You can see them if you look at the tips of the shoots, pulling the leaves back to expose the flower buds. This is not the case with hibiscus, as the flower buds are formed on new growth in late spring and summer. If you do much pruning on azaleas now, you will remove the flower buds. It’s best to prune azaleas shortly after they flower but before July.