Answer: Neither rhododendrons or hydrangeas need to be cut back in the fall. To keep hydrangeas attractive, and to promote flowering, you can prune back the stems that have already flowered, but leave those that have not yet flowered. Cut the stems all the way to the soil level. Rhododendrons don't need regular pruning, but remove the flower trusses after they fade by carefully snapping them off. Be careful not to damage the green buds below the flowers. Those buds are this year's leaves and next year's blooms. When rhodies get lanky you can cut the branches back to a bud or all the way to the trunk. New stems and branches will grow wherever you make a cut. It will take about two years for those branches to produces flowers.
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