During August, a client wanted to know whether now was the correct time to prune hydrangea bushes. The type of hydrangea was not known.
DIAGNOSIS / RECOMMENDATION:
While this question came in in August, the proper timing of pruning really depends on knowing the type of hydrangea, spring blooming or summer blooming. Regardless of type, however, August through December is not an appropriate time to prune hydrangeas. 
There are several different types of hydrangea. Smooth hydrangea (Hydrangea arborescens) is a Virginia native species and is found in many gardens. It blooms on new spring growth, and pruning should be done in the early Spring.  In contrast, Oakleaf hydrangea (H. quercifolia), a native to Georgia to Mississippi, blooms on the previous year’s growth. Bigleaf hydrangea (H. macrophylla) also bloom on last year’s growth; this includes both mophead and lacecap types. For types blooming on last year’s growth, late year or early Spring pruning will remove all the blooms for the year. These types should be pruned in June or July once blooming is over. [2, 3]
There are some ever-blooming varieties of Bigleaf hydrangeas that actually bloom on both new and old wood; care still is needed to avoid removing the blooms for the current year. [2, 4]
It really is not necessary to prune hydrangeas at all, and that may be a better option than pruning improperly. A simplified approach, suitable for all types of hydrangeas, is to limit pruning to:
- “Winter-killed wood — Remove all dead branches in the spring before or as the buds are opening. Test the stem for life by scraping the bark with a knife. If it’s not green underneath, it’s dead and should be removed.
- Rejuvenation — Old wood dies back on even the healthiest hydrangeas. In the early spring remove dead or very old stems by cutting them at the base of the plant. This will stimulate new growth and produce a more vigorous bloom set later in the summer.
- Dead flowers —Removal of old dried flowers, known as dead-heading, is the safest pruning and can’t be done incorrectly.” 
Pruning can be helpful in ensuring good health of the plant, including improving air circulation to help minimize disease problems. [2, 4] It is important to be sure of the type of hydrangea and then to prune only during the proper times of year. 
From The Bedford Extension MG Help Desk
Betsy B., Bedford Extension Master Gardener Volunteer; Help Desk Co-Coordinator
SOURCE: Aug2017 Pruning Hydrangeas_FTHD
PHOTO CREDITS: Hydrangea macrophylla from Bedford Extension Master Gardener KathyN’s garden
All resource links accessed July 16, 2017
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