Categories: Flowers & Shrubs

How to Overwinter Hydrangeas So They Bloom Next Year

Hydrangeas are tough shrubs, but their flower buds aren’t. For bigleaf and oakleaf types, next summer’s blooms are already sitting at the tips of the stems in fall. Knowing how to overwinter hydrangeas is really about protecting those buds from cold, wind, and late frosts.

The good news is that learning how to overwinter hydrangeas takes only an afternoon and a few simple materials.

Which Hydrangeas Need Winter Protection?

Bigleaf (mophead and lacecap): Need the most help, especially in USDA zones 5 and 6.
Oakleaf: Usually fine in zone 6 and warmer; protect in zone 5.
Panicle and smooth: Bloom on new wood, so they rarely need protection. In fact, they handle zone 3 or 4 winters easily.
Potted hydrangeas of any type: Always need extra care, because roots in containers freeze more easily.

If you’re not sure which you have, our guide on when to prune hydrangeas explains how to tell the types apart.

How to Overwinter Hydrangeas in the Ground

1. Stop Pruning in Late Summer

First, put the pruners away after early August for old-wood types. Every cut after that removes flower buds.

2. Water Until the Ground Freezes

Next, give shrubs a deep watering every week or two in fall if rain is scarce. Well-hydrated plants handle cold better.

3. Leave the Old Flower Heads

Dried blooms look lovely in winter. More importantly, they shelter the buds just below them. Wait until spring to remove them.

4. Mulch the Base

After the first hard freeze, pile 8 to 12 inches of shredded leaves, pine needles, or straw around the base. This protects the lower buds and the crown.

Late spring freezes cause more damage than steady winter cold.

5. Build a Cage in Cold Zones

In zones 5 and colder, go a step further. Circle the shrub with chicken wire or hardware cloth staked a few inches out from the branches. Then fill the cage loosely with dry leaves. Finally, cover the top with burlap to shed rain. Avoid plastic, which traps moisture and heat on sunny days.

6. Remove Protection Gradually

In spring, take the leaves out once the danger of hard frost has passed. However, keep a sheet or burlap handy. A single late frost after buds swell can wipe out a season’s flowers.

How to Overwinter Hydrangeas in Pots

When you overwinter hydrangeas in containers, remember that roots are exposed on every side. Therefore, potted hydrangeas need a different approach.

Move the pot into an unheated garage or shed after the leaves drop. Temperatures between 25 and 45°F are ideal.
Water lightly once a month so roots don’t dry out completely.
Bring it back outside after your last frost, starting in shade and moving into its normal spot over a week.

Alternatively, if you have no garage, sink the pot into the ground in a sheltered spot and mulch heavily. Our guide on how to overwinter potted plants covers more methods.

Leave old flower heads on to shelter buds below.

Common Winter Mistakes

Cutting back in fall: This removes buds on old-wood types.
Wrapping too early: Wait until the plant is dormant, or it may rot.
Using plastic: It overheats plants on sunny winter days.
Unwrapping too soon: Mild March weather often comes before a hard April freeze.

If last year’s shrub leafed out but never flowered, winter damage was probably part of the reason. See our guide to a hydrangea not blooming for other causes.

Overwintering Hydrangeas in South America

In most of Brazil, hydrangeas (hortênsias) grow in mild highland regions like the Serra Gaúcha, where winters bring occasional frosts. The same steps apply there in June and July: leave old flower heads, mulch the base, and cover plants on frosty nights. In Patagonia and southern Chile, where winters are colder, the full cage method works well.

Check Your Zone

Winter protection depends on how cold it gets where you live. Look up your zone on the USDA Plant Hardiness Zone Map before deciding how much protection your shrubs need.