Hydrangeas are relatively easy to grow and usually require little in the way of maintenance. They are deciduous plants that are not very attractive during the winter. The old branches look woody and often dead, although they will bounce back to life in the spring.
Nevertheless, some varieties are more tender than others and if you are in a colder region, then you will want to protect hydrangeas from the cold and from frost damage.
If you prepare the hydrangea well for the winter, you will minimize the likelihood of winter damage that could otherwise result in a loss of flower buds, or worse. The plant will also be protected and suffer less from stress damage. This helps the plant to bounce back quicker and better after a cold snap.
Does a Hydrangea Need Winter Protection?
Many hydrangeas are considered hardy, and some are semi-hardy. In theory, hydrangeas are tolerant of temperatures as low as freezing point (0° C). Unfortunately, weather conditions are becoming more and more unpredictable. Each season, there are wild swings in temperature and fluctuating levels of snow.
Snow is a naturally insulating material, but can no longer be relied upon to provide necessary plant protection. Although most hydrangeas will not die if there is a short period of frosts, buds, and tender new stems are susceptible to damage. You may lose flowers if you don’t cover your hydrangea shrub during the coldest periods.
Hydrangea paniculata and Hydrangea arborescens are hardier than the bigleaf varieties such as the mophead and lacecap hydrangeas, which flower on old wood. But the new varieties of bigleaf hydrangeas which bloom on both old and new wood are also hardier.
Cutting Back Your Hydrangea
You need to be wary of pruning hydrangeas in winter. If it is a variety that blooms on old wood, you should not prune hydrangeas after early summer. By this time, when the current year’s flowers are still in bloom, the following year’s flower buds will be in development on the plant’s stems. Cutting back or pruning these hydrangeas at this stage will result in cutting off the following year’s flowers.
Conversely, if you have a hydrangea that flowers on new wood, this plant should be pruned in late winter, before the new growth starts to develop in early spring.
So, no hydrangea, or any perennial shrub should be pruned in the autumn or early winter.
Preparing Hydrangeas for Winter
Before providing a mulch or protective cover for your hydrangea shrub, you should apply some compost around its roots. Don’t mistake this for fertilizer! You certainly don’t want to be applying a nitrogen-rich fertilizer at this time, as this will lead to new growth that will not be sufficiently robust to survive the winter.
But a top dressing of organic matter, such as compost or well-rotted garden manure, is ideal. The compost will break down during the winter and release its nutrients slowly. They will be available for the plant in the spring.
Protecting Hydrangeas for Winter
In practice, it is only practicable to completely cover a small or compact hydrangea shrub. A larger plant will be too tall and wide to cover.
Pot Grown and Small Hydrangea Plants
A pot-grown plant is more at risk of frost damage than a plant growing in open ground. The roots in the pot are more exposed and much more likely to freeze, especially if the growing medium is wet. There is no insulation provided in a pot equivalent to that provided by the ground.
Fortunately, a hydrangea growing in a pot is easier to move to a sheltered position or indoors during a cold snap. If the pot is large or heavy, it can be moved easier on a plant trolley.
If the pot-grown hydrangea has to stay outdoors, provide a protective cover for it. Don’t use plastic as a covering material; it can cause condensation, which can freeze and augment the problems during a frost. Instead, find a breathable fabric cover that you can use to wrap around the plant.
Large Hydrangea Plants
A larger plant may require more substantial work to protect it. You will have to construct a framework with wood and cover it with chicken wire. You can then throw inside the cage whatever you have in the way of dry mulch material such as straw, large-sized leaves, or pine needles.
Winter Care of Hydrangeas
Watering and Feeding
Hydrangea bushes still require moisture, even during winter. Unless the ground is frozen hard, you should continue to water your hydrangeas, but infrequently. If you have a wet period, with plenty of rainfall, you might not need to water at all. You don’t want the plants to sit in soggy soil, as this can easily lead to root rot.
If you have covered your hydrangea shrub, then the easiest way to water is to set a bucket filled with water at the base of the plant. Make a small hole in the side of the bottom of the bucket. The water will escape slowly around the hydrangea’s roots.
If you have applied a mulch before covering your plant, this will slowly leach the nutrients into the soil in readiness for the spring. It can’t be overstated enough, but do not be tempted to give any application of fertilizer to your hydrangea in winter.
Uncovering the Hydrangeas in Spring
A hydrangea is most vulnerable in the spring. By spring, it will have developing flower buds that are tender and prone to a late frost. If these buds are frost-damaged at this stage, they are likely to fall off. You will have lost the current year’s flowers.
Spring Damage can do a lot of damage to hydrangea plants, and therefore you shouldn’t be tempted to remove the protection too soon. It’s much better to wait an extra week until the temperature warms up than remove too early and have dead branches. Don’t worry that your plant will be behind, as foliage and buds will soon catch up once you do release them!
Check the official date of the last frost with your department of agriculture. This can be anywhere from mid-April to mid-May depending on your zone, but there are always exceptions! Erratic and unpredictable climatic conditions have become more and more “normal”. So keep an eye on meteorological forecasts. If you have uncovered too early and a frost is protected, be prepared to throw a blanket or protective cover over as much of the plant as you can.