How to Prune Hydrangeas: Old Wood, New Wood and August 1

Prune a bigleaf hydrangea (Hydrangea macrophylla) right after it flowers, and do not cut it after August 1. It blooms on old wood, meaning last year’s stems carry this year’s flowers, so a cut in fall, winter or early spring removes the blooms. Clemson says the best time to remove dead canes or rejuvenate an older plant is immediately after flowering. The one real disagreement is the cutoff date: Clemson says avoid pruning after August 1, NC State says do any pruning before August 1, and Oregon State says late summer after flowering. This guide sits under our hydrangea care guide.

Old wood or new wood?

NC State says bigleaf hydrangea blooms in late spring and summer on the previous year’s growth. That is old wood. Penn State is blunt about the cost: “If you cut back a hydrangea between the autumn and early spring, and it blooms on old wood, you have trimmed off all the future flowers!” Oregon State sorts the types.

If you do not know which type you have, check the label or ask the nursery before you cut.

The August 1 conflict

The sources give three versions of the same rule.

The cautious reading is the one two sources agree on: finish by August 1. Oregon State’s wording is looser and gives no date, and it is written for Oregon rather than South Carolina.

How much to remove

Oregon State says to avoid removing more than one-third of the plant at a time. Clemson says that if you must prune in winter or spring after buds have formed, remove no more than one-third. Clemson also says to remove dead canes, and says the best time to rejuvenate an older plant is immediately after flowering.

1. Wait until the flowers fade. Prune immediately after flowering (Clemson).
2. Finish before August 1. Clemson and NC State both give this line. Oregon State says late summer.
3. Remove dead canes first. Clemson lists removing dead canes as the best job to do right after flowering.
4. Never take more than a third. Oregon State’s limit per pruning.
5. Do not cut in fall, winter or early spring. Penn State says that removes all the future flowers on an old-wood plant.

If you pruned at the wrong time

Penn State says freezes can also destroy the flower buds and stems each year, so a plant that did not bloom may have been pruned too late or been hit by cold. Our not-flowering guide covers the checks. Clemson says that for late cold snaps, the best you can do is watch the weather and cover the canes with frost blankets. Our overwintering guide has that.

What our sources do not say

They give no pruning schedule for reblooming types specifically, no cutting height and no advice for container plants. Penn State and Clemson both stress the old-wood rule, and none of the five sources conflicts with it. For the rest of the year’s care, see our hydrangea care guide.