Answer: The big leafed hydrangeas bloom on old wood, so any pruning should be delayed until the plants have leafed out fully. Then, remove only the oldest stems on overgrown plants, and any winter damage. In most cases using a fertilizer for acid loving plants is sufficient to maintain the soil acidity necessary for blue flowers. If you think the blooms should be bluer, it is a good idea to run some basic soil tests and then slowly adjust the pH based on the results. Your county extension should be able to help you with the tests and interpreting the results as well as advise what to use and how much of it at a time.
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