|When, where, and how do you prune rhododendrons?
|One bit of annual maintenance that will help your rhododendrons maintain flowering is called deadheading. You should remove the spent flower trusses after the plant has finished flowering. A great deal of the plant's energy can be diverted toward seed production, and by deadheading you divert that energy back into vegetative growth. Once the flower heads have dried a bit, you should carefully break them off at the base, being careful not to damage the small growth buds surrounding the base.
Normally very little pruning is needed. If a plant grows out over a walk or needs to be restricted for some reason, it may be pruned back moderately without fear that the plant as a whole will be damaged. It is often possible to do this pruning during the blooming season and have flowers for the house. Light maintenance pruning at the time "dead-heading" is done can help keep the plant in shape. Light to moderate pruning done at the time the plant is flowering or immediately thereafter will not affect flower bud formation for the following year. Sometimes, as the plant starts to grow, only one growth bud at the end of a stem will begin to expand. If this single bud is broken out just as it starts to enlarge, it will cause two or more dormant buds at the end of the stem to expand, making a bushier plant. Again, this will not affect bud set for the coming year. Old leggy plants may need pruning, but often these are better replaced with smaller newer varieties. Old plants, however, can be cut back severely and still recover, although it may be a while before they bloom again.