Hydrangea Fall Care: Protecting Buds Through Winter

Fall hydrangea care for bigleaf types is mostly about what not to do: do not prune, and be ready to cover the canes if a cold snap threatens the flower buds. Penn State says the roots of hydrangeas may be hardy but the top of the plant is not, and that early or late freezes or bitter winters may damage the flower buds. A bigleaf (H. macrophylla) blooms on last year’s growth, so the buds that formed this summer are next year’s flowers. This guide sits under our hydrangea care guide.

Why fall is a protecting season, not a pruning one

NC State says bigleaf hydrangeas bloom on the previous year’s growth. Penn State says that 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. Clemson says to avoid pruning after August 1 to prevent removing next year’s buds. So leave the canes standing through winter, and see our pruning guide for the timing and the August 1 conflict.

Reblooming types are different. Clemson, Penn State and Oregon State say that reblooming types such as ‘Endless Summer’ bloom on both old and new wood, so a mistimed cut costs them less.

Protecting canes and buds

Penn State describes winters in which the flower buds and/or the stems freeze, destroying the future flowers. Clemson says that as for late-season cold snaps, all we can do is watch the weather and provide protection by covering the canes with frost blankets when needed. Our sources do not name a temperature at which to cover, so watch the forecast for the coldest nights of late fall and spring.

Potted hydrangeas

Oregon State says that in colder interiors you can grow bigleaf and serrata hydrangeas in large containers and overwinter them in an unheated garage to protect the buds. NC State says a single specimen can be grown in a container. Our sources do not say when to move the pot in, how cold the garage may get, how often to water it or when to bring it back out, so we cannot give a schedule. Oregon State’s wording is an unheated garage, with the stated aim of protecting the buds.

Soil changes in fall

Oregon State says that if you want to change flower color, amendments are best added in fall, and that color changes may take several years. Clemson says always to test your soil before applying sulfur or lime to avoid over-correction. See the color section of our main hydrangea guide for pH ranges, which differ by source.

Fall checklist

1. Do not prune a bigleaf now. Clemson says avoid pruning after August 1; Penn State says a cut between autumn and early spring removes the flowers.
2. Leave the canes standing. They carry next year’s flower buds (NC State, Penn State).
3. Watch the forecast. Cover canes with frost blankets before a late cold snap (Clemson).
4. Move container plants to an unheated garage in colder regions. Oregon State’s method for protecting buds.
5. If changing color, test soil and amend in fall. Oregon State says fall is best; Clemson says test first.

What our sources do not say

None of our sources gives leaf-drop timing, mulching advice, a winter watering schedule or a cut-off temperature for covering. They agree on the main point: protect the buds, do not prune old-wood types in fall. For more about why a hydrangea does not bloom, see hydrangea not flowering. Back to the hydrangea care guide. Fall is also bulb-planting season: if tulips are on your list, see when to plant tulip bulbs and our fall bulb planting guide.