When should hydrangeas be pruned? When should rhododendrons be pruned? What is dead-heding?
For both plants, you only need to remove dead wood with some regularity. In the south, pruning of dead wood happens after the end of May i case the stems are alive and leafing out late. Further north, you can wait until June or even July. If you need to prune live wood in hydrangeas that bloom on old wood, do so after the plant stops opening flower buds. For hydrangeas that bloom on new wood, avoid pruning somewhere from mid spring to as late as late summer/fall as that is a period when those hydrangeas develop flower buds and open flowers. Rhododendrons should also be pruned after the flowers begin to fade. Removal of the spent flowers is what is called deadheading and it can be done at any time. Deadheding hydrangeas does not encourage reblooming as you get a maximum of one bloom per stem per year with any hydrangea. It typically consists of short cuts of the stems (say, the first set of leaves); you can also cut at the peduncle, the string that attaches blooms to the stem. If the cut is short, you do not interfere much with any flower bud development that could be going on.