Hydrangeas are gorgeous, hardy shrubs that can take the summer heat and chilly winter temperatures. The large flowers can last up to 20 growing seasons with some proper care during the changing seasons. When getting your hydrangeas ready for the winter, it's important to follow these steps to ensure your shrub blooms next spring. Here, we'll discuss when to winterize your shrubs, which hydrangeas to prune, and more ways to prepare them for winter.
When To Winterize Hydrangeas
When is the best time to winterize your hydrangeas to optimize for big blooms next season? In cooler climates, it's essential to prepare your shrub in late fall, just a few weeks leading up to the first frost. In warmer clients, some light winterizing, as discussed below, might be necessary at the beginning of November; otherwise, you're good to grow! Remember to keep an eye on the weather report: states with somewhat unpredictable weather, like Michigan, for example, may experience frigid temperatures much earlier than anticipated.
To Prune Or Not To Prune?
The short answer is no. Pruning your hydrangeas just before winter will leave them even more susceptible to winter damage, and you're at risk for cutting off future flowers. Here's a snapshot at our guide for pruning hydrangeas:
- If it blooms on new wood: Pruning is optimal in late winter or early spring. We're talking about panicle hydrangeas (H. paniculata) and smooth hydrangeas (H. arborescens), which create their flower buds in early spring after dormancy. Prune them just as green leaf buds start to emerge to encourage new growth and stronger stems.
- If it blooms on old wood: We don't recommend pruning at all! Old wood hydrangeas create their flower buds for the next year right when they finish blooming in the current year, so you're at risk for cutting off future flowers. This group includes bigleaf hydrangeas (H. macrophylla), mountain hydrangeas (H. serrata), oakleaf hydrangeas (H. quercifolia), cascade hydrangeas (H. x), and climbing hydrangeas (H. petiolaris)
One Last Watering
The cold and dry weather can be hard on hydrangeas during the winter months! Since hydrangeas are water-loving shrubs, it's important to give them one last thorough and deep watering before the ground freezes. When hydrangeas receive a deep watering before winter, their roots can hold on to moisture that will carry them through spring.
Mulch To Conserve Moisture
Hydrangeas thrive in moist soils, and your shrub must be kept hydrated through the cold and dry winter months. Adding mulch to your hydrangea after thoroughly watering helps retain moisture (and warmth) at the shrub's crown when temperatures drop. Use a thick layer of hardwood mulch, up to 12 inches at the base of your hydrangea, and that's it!
Do NOT add fertilizer: you will not want to encourage new hydrangea growth before the first freeze, as this leaves your shrub vulnerable to damage from frigid temperatures, thus delaying or significantly reducing blooms come spring/summer.
Covering Your Hydrangeas
Many gardeners also wonder if keeping their hydrangeas completely covered during the winter is a good idea. If you've followed the proper winterization steps, your hydrangeas should be just fine left uncovered during the winter. However, there are a few exceptions. Hydrangeas that bloom on old wood may need extra protection on extremely frigid nights (0 degrees Fahrenheit or below).
You can easily cover it with burlap or even standard household blankets. If snow accumulates on top of the covering, brush it off frequently, as the weight could cause the canes to snap or the shrub to topple over.