Most gardeners are fond of their hydrangea shrubs, whether they plant the mophead variety with globes of flower clusters or shrubs with panicles or lacecap flowers. Hydrangea cold tolerance varies among varieties and winter kill on hydrangeas is not a pretty sight. Many hydrangea species and cultivars are winter hardy, but only to a point.
Proper hydrangea care in winter can determine the success and quantity of next summer's blooms. Erratic winter weather can be particularly damaging to shrubs, which can lead to poor or no flowering the following season. So the key is to protect your plant prior to the first frost in winter all the way through the last frost in spring.
If you want to ensure your hydrangeas are full of gorgeous flowers next summer, follow these tips to protect plants and ensure consistent blooms. Here’s how to winterize your hydrangeas now before winter weather sets in.
Hydrangea Cold Tolerance
Hydrangeas are among the easiest shrubs to grow. They put out huge blooms all summer with minimal care. But when summer ends and winter sneaks in, it’s important to know how to protect hydrangeas from cold. The first step is understanding hydrangea cold tolerance.
Some varieties, like smooth hydrangeas (Hydrangea arborescens) and panicle hydrangeas (H. paniculata), are very cold hardy and bloom on new wood. If these are the species in your garden, you don’t have to worry about winter kill on your hydrangeas.
They don’t need protection unless the temperature dips below negative 30°F (-1°C). In fact, leaving foliage over winter can actually help protect these plants and serve as additional winter interest in the garden.
All of the other hydrangea varieties, including the popular mophead hydrangea (H. macrophylla), bloom on old wood. That means they form flower buds the year before they bloom. These young buds need to survive the winter for you to see flowers the following summer.
If you grow a variety that blooms on old wood, learning how to prevent winter kill on hydrangeas is vital for good flowering. This is especially true if you live in a colder USDA planting zone.
What Is Winter Kill?
Cold isn’t the only concern when it comes to winterizing hydrangeas, however. Winter wind, in addition to cold temperatures, can also impact hydrangea health and cause winter kill. “Winter kill” is a general term that simply means plant death that occurs during the winter season. Low winter temperatures can kill plants, but wind can also dry out plants and make them die.
Since hydrangeas go dormant during the winter, you may not notice winter kill on hydrangeas until spring. Your first hint of damage may be the fact that no green shoots emerge from your hydrangea in March or April.
Preventing winter kill is a matter of protecting your shrubs, including their nascent buds, from winter’s wrath. This starts by properly caring for your hydrangeas in fall and following a few simple tips. The winterizing techniques below will help protect your hydrangeas from winter kill and ensure you have shrubs full of flowers next summer.
How to Prepare Hydrangeas for Winter
Even if you’ve picked the best hydrangeas for your growing zone and the variety you planted is meant to be cold hardy, it’s still a good idea to prepare shrubs for the winter season. Protecting a hydrangea in winter ensures the plants remain healthy and continue to flower every year.
1. Add Compost
If you make your own compost, add a top dressing at the base of your hydrangea shrubs. A couple inches of compost will break down over the winter months and slowly add nutrients to the soil. When shrubs begin growing again in spring, your hydrangeas will have plenty of nutrients available to help them put out plenty of blooms.
2. Water
Hydrangeas need a lot of water, even in winter. In fact, the cold air and wind in winter pulls extra moisture out of shrubs. That means they potentially need even more water then during the temperate parts of the growing season.
Keep watering hydrangeas right up until the ground freezes. If your ground doesn’t freeze, continue to water year round. In more temperate winter climates, water hydrangeas deeply but infrequently as you would during the growing season.
3. Provide Protection
The most important thing your hydrangea needs for winter is protection from cold temperatures and drying winds. Start with mulch. Apply a thick layer of mulch around each shrub, to a depth of about six inches (15 cm). Straw works well for this. Stock up on straw mulch from Amazon now before winter weather hits.
The mulch will insulate the base of the plant and roots. It will also protect it from freezing and thawing cycles that can push a plant’s roots right out of the ground. The best time to apply mulch is right after the ground freezes. Any earlier, and you invite pests to nest in the warm mulch. Don’t wait too late, though, or an early freeze could hurt hydrangeas.
If your garden gets winter temperatures below 0°F (-18°C), consider adding an additional barrier to protect hydrangeas. Place stakes in the ground around the shrubs and wrap them in burlap. Staple or tie the burlap to the stakes to prevent it from blowing away in the wind.
Alternatively, you can cover small shrubs with wire tomato cages or build a cage around hydrangeas using strong stakes and chicken wire. Wrap burlap or insulation cloth around the cage. Wrap chicken wire around the stakes to form a cage.
Fill the cage with pine needles or leaves to fully insulate your plant. Oak leaves work well because they do not settle as easily as other materials. Keep a bag of leaves from your fall raking so you can fill the cage throughout the winter as the insulation settles.
Be careful not to snap off the ends of the branches as you fill the cage or all will be for naught and you won't get those gorgeous blooms next summer.
Caring for Hydrangeas in Winter
Your hydrangeas will not need a lot of care during the winter months, but some maintenance will help keep them healthy and happy. If the ground doesn’t freeze in your garden, keep watering hydrangeas all the way through winter. Provide regular, but infrequent deep watering when there is no rain.
Check on hydrangeas throughout the winter season. If you wrapped them in burlap, make sure the wrapping is still intact and secure. Keep the mulch layer deep. Reapply mulch if any blows away in the wind.
If you did not wrap your hydrangeas at the beginning of the winter season, but temperatures are dropping, you can add burlap at any time. You can also use snow to help insulate plants. Bury the shrubs under snow to protect them from subfreezing temperatures and wind.
Winterizing Potted Hydrangeas
The best winter protection for potted hydrangeas is to bring them inside prior to the first frost. Put them in a garage or a cool basement for the winter.
Though you can grow hydrangeas indoors for a short amount of time, they don’t do well as year-round houseplants. Instead of trying to keep them growing all year, let them go dormant outside or in a cool, dark indoor space.
If your potted hydrangeas are too large or cumbersome to move, invest in a plant caddy, like one of these from Amazon. This makes the job much easier. You can also sink pots into the ground for better root protection from cold. Or cover the entire pot and plant with burlap the same you would an in-ground shrub.
Can I Prune Hydrangeas in Winter?
Resist the urge to prune hydrangeas in fall or early winter. Pruning at this time could stimulate new growth that will freeze over the winter. Instead, prune hydrangeas in late winter or early spring.
Make sure you know which type of hydrangea you have to determine how and when to prune. Some develop buds on new growth and others on old growth, so trimming the wrong branches can reduce blooms.
However, if there are any dead or diseased branches on your hydrangeas, you can remove those at any time. Be careful, though, not to cut off any healthy wood. And always clean your pruners between plants to prevent spreading disease. Content Editor Laura Walters recommends using disinfectant wipes, like these ones you can get on Amazon, to make sanitizing pruners simple.
Shop Winterizing Essentials
Move potted hydrangeas indoors with ease with these plant caddies.
Keep hydrangeas warm and toasty with a burlap wrap.
Protect tender roots from cold winter winds with organic mulch.
