Hydrangea bushes are a gardener's delight for many reasons. Above all, these showy shrubs will provide abundant blossoms during the summer with little maintenance or coaxing. In addition, hydrangea shrubs do not require extensive trimming or pruning to keep them healthy and attractive. When you trim your hydrangea bushes depends upon what variety of hydrangea you grow. You must prune some hydrangea only in the early part of the growing season to prevent removing future blooms. Other hydrangeas are more adaptable, and you can prune these hydrangeas at almost any time of the year without risk to future blooms.
Examine your hydrangea and determine which variety of hydrangea you are growing. Lacecap or Mophead hydrangeas are often blue or pink. Oakleaf hydrangeas bloom white, and they have the characteristic oak-shaped leaves. These varieties bloom on old growth. Other white-blooming hydrangeas could likely be varieties that bloom on new growth. To be sure of the pruning method you should use, it may be best to observe your hydrangea shrubs' blooming pattern. If the shrubs bloom on old growth, the timing of the pruning is important. If the shrubs bloom on new growth, the timing is less important.
Prune hydrangeas that bloom on old growth carefully to avoid disrupting future blooms. These hydrangeas develop future blooms in late summer and early autumn. If you prune any time after these blooms develop, you will remove the blooms. The safest time to prune these hydrangeas is immediately after it blooms and before the new blooms develop. To prune, simply remove spent blossoms. You can also control the size of these hydrangeas by removing as much as one-third of the top growth (cutting anywhere along the stems).
Trim hydrangeas that bloom on new growth with less concern over timing. The only time of the year you should not prune these hydrangeas is immediately before they bloom (because you would be removing blooms). Remove spent blooms when they fade. Some gardeners prefer to cut these shrubs back to the soil level each year and others merely shape these shrubs to control their size. You do not even have to prune hydrangeas if you choose not to.
Deadhead hydrangea shrubs (either type) to keep the hydrangeas attractive. If you deadhead before new blooms develop (before late summer), cut the stems as long as you desire. If you deadhead after this time (late summer or early autumn), remove the spent blossoms only and do not clip off the stems.