Hydrangea Winter Care: Fall Pruning, Cages and Mulch

More on hydrangeas

• Hydrangea planting zones — every type, the zones it suits, and when the last spring freeze lands in each zone
• Why Is My Hydrangea Not Blooming? Causes and Fixes
• How to Prune Hydrangeas by Type: Old Wood vs New Wood
• How to Change Hydrangea Color: Blue or Pink by Soil pH
• How to Prune Limelight Hydrangea and Vanilla Strawberry
• How to Prune Annabelle and Incrediball Hydrangeas
• How to Prune Endless Summer Hydrangeas (Rebloomers)
• How to Prune Oakleaf Hydrangea: After It Flowers
• Hydrangea Pruning Chart: When to Prune Each Type
• Hydrangea Tree Care and Pruning (Tree-Form Panicle)
• Hydrangea Winter Care: Fall Pruning, Cages and Mulch — this page
• ZIP code zone finder — your exact USDA zone, to read the tables on these pages against

Which hydrangeas need winter care

Penn State Extension says bigleaf hydrangea can be killed to the ground in a cold winter, which means no flowers the next summer, and even a moderately severe winter can kill or damage the flower buds. Clemson Extension, writing for South Carolina, says winter injury is the most common reason hydrangeas fail to bloom.

Fall pruning: the mistake that looks like care

Minnesota says bigleaf hydrangeas form next year’s flower buds in late summer to early fall, August to September. From then on the stems carry next summer’s flowers. Ohio State says an old-wood hydrangea pruned or cut down in fall has little to no bloom the next year; UNH says never prune bigleaf hydrangeas in late summer or fall; Cornell Cooperative Extension in Orange County says pruning bigleaf hydrangea after September eliminates flower buds, and any new growth will not mature before winter. Penn State says deer browsing does the same damage.

Panicle and smooth hydrangeas are different: they flower on new wood. Ohio State says smooth hydrangea can be cut down in late fall or very early spring, and Minnesota says panicle hydrangea can be cut in fall but suggests waiting until late winter or spring so the flower heads stand through winter. The full fall list is in what not to prune in fall.

How to protect an old-wood hydrangea

1. Leave the stems. Ohio State says protecting three buds is enough for next year’s flowers, so you can prune back to just above the third bud on each stem and protect what is left.
2. Build a cage. Oregon State Extension puts a cylinder of chicken wire or a tomato cage around the plant. UNH wraps the plant with burlap or chicken wire. Cornell Cooperative Extension ties the shoots together and wraps them in burlap.
3. Fill it with leaves. UNH and Oregon State fill the enclosure with leaves; Ohio State uses mulch or leaves and compost. Oregon State says a layer of leaves insulates and keeps roots dry, and that a wet winter with heavy rain does more damage to flowers than a cold one.
4. Wrap the outside. Oregon State surrounds the cage with fabric, which it says keeps moisture off the plant and stops snow from breaking branches.
5. Guard against rabbits. Minnesota protects bigleaf stems with a 4-foot-tall ring of hardware cloth, and hydrangeas generally with 24-inch wire fencing.

UNH adds that heavy snow cover can protect the buds, though no one can count on it, and that even wrapping is not always enough. If a plant still does not flower, UNH suggests moving it somewhere more sheltered or growing a cultivar that flowers on new wood more readily. Ohio State says a gardener who cannot give winter protection should choose a cultivar that flowers on both old and new wood.

In spring: uncover, then watch for frost

Ohio State removes the winter protection once new leaf buds begin to emerge, in late March for Ohio, then protects against hard frosts in April and early May. UNH waits until all danger of frost has passed. Oregon State covers the buds with bed sheets or frost cloth on nights a spring frost is forecast.

Then prune what winter killed: Iowa State says wait until the shrubs begin to leaf out, then remove all dead wood. The variety pages have the details, from Endless Summer to oakleaf. For frost covers on other plants, see how to protect plants from frost.

Common mistakes

• Cutting old-wood hydrangeas back in fall. Little to no bloom follows (Ohio State).
• Uncovering and forgetting. Ohio State says a late spring frost undoes the winter’s work.
• Covering a panicle or smooth hydrangea for its flowers. They flower on new wood (Penn State).
• Leaving stems to rabbits. Minnesota fences them.
• Pruning dead wood before leaves show. Iowa State waits for leaf-out to see what is dead.

For winter damage on shrubs generally, wind, salt and snow included, see how to protect shrubs in winter.

In the South

Winter matters in the South too: Clemson, writing for South Carolina, says winter injury is the most common reason hydrangeas fail to bloom. Its advice there is to prune bigleaf hydrangeas right after flowering and keep a 2 to 3 inch mulch layer. We found no Texas A&M or LSU source on hydrangeas in winter, so advice for Texas and Louisiana here is limited; ask your county extension office.