How you prepare a hydrangea for winter depends mainly on the species. Panicle and smooth hydrangeas survive hard frosts with little help, while bigleaf hydrangeas need careful protection, or their flower buds die and there will be no blooms next summer. Here is how to prepare each species, when and how to cover them, whether to prune in autumn, how to overwinter potted hydrangeas and when to uncover them in spring.
Approximate hardiness of mature plants; young bushes in their first two or three years are always protected.
Autumn tasks for every hydrangea
Stop nitrogen feeding from mid-August, as it pushes soft new shoots that will not ripen in time. Give a phosphorus and potassium feed instead: a tablespoon each of superphosphate and potassium sulphate in 10 litres of water per bush, or a special autumn fertiliser. Repeat after two or three weeks.
If October is dry, give a deep pre-winter watering of 20–30 litres per mature bush. Moist soil freezes more slowly, and roots cope better with frost. Then mulch the root zone with 10–15 cm of peat, bark, compost or pine needles.
Should you prune in autumn
Bigleaf, mountain and oakleaf hydrangeas are not pruned in autumn: next season's flower buds are already set at the tips of this year's canes. You can only remove dry flower heads carefully, down to the first pair of healthy buds. More on this species in our article on bigleaf hydrangea.
Panicle and smooth hydrangeas get their main pruning in spring, as they bloom on new wood. In autumn, though, cut off the heavy flower heads: wet snow sticks to them and breaks the branches. How to prune them in spring is covered in our articles on panicle and smooth hydrangea.
How to cover a bigleaf hydrangea
Cover the plant after the first light frosts, once temperatures hover around −3…−5 °C, usually in late October or November. Do not do it earlier, or the plant may rot under the cover. Strip the leaves except those at the tips that shield the buds, and spray the bush with a copper fungicide.
Tie the canes together gently and bend them down onto a layer of spruce branches or boards, pinning them with wire hoops. Cover with dry leaves or sawdust, then spruce branches and two layers of fleece, and finally plastic sheeting with open edges for ventilation. If the canes will not bend, build a mesh cage around the bush, fill it with dry leaves and wrap it in fleece.
Potted and young hydrangeas
Bring containerised hydrangeas into a cool, dark or dim place for winter, such as a cellar, garage or glazed balcony at 2–8 °C. Water rarely, just enough to stop the root ball drying out. Dropping leaves is a normal response to dormancy. More on care in our article on hydrangeas in pots.
Young plants in their first two or three years, as well as rooted cuttings, are protected regardless of species. How to grow a new bush and care for it in its first year is covered in our article on propagating hydrangeas from cuttings.
When to uncover in spring
Remove the cover gradually, in several stages, from late March to late April. First open the edges of the plastic for ventilation, then take it off, leaving the fleece in place until hard night frosts are over. Late frosts down to −5 °C can kill bigleaf hydrangea buds, so keep fleece at hand and watch the forecast.
Once uncovered, trim only frost-damaged tips back to the first live buds and give a nitrogen feed. If the canes died back to the ground, the bush will regrow, but only remontant varieties such as Endless Summer will flower that season. Find more tips in our hydrangea guide.
Hydrangea bouquets delivered in Kyiv
While garden hydrangeas sleep under cover, cut ones are available all year. Order a bouquet of white or lavender hydrangeas or put together your own arrangement with delivery across Kyiv.
Graduated from Taras Shevchenko National University of Kyiv, Institute of Biology and Medicine (2001). BSc in Biology, MSc in Horticulture. Writes about plants, works at a garden centre selecting and repotting plants, and contributes to plant reference guides.
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