Place cloth over any blooming or budded up shrubs. If possible, drape cloth to the ground and secure. Big Leaf Hydrangeas, Hydrangea maculata, do not tolerate frosts well and should be covered to prevent leaf damage and flower loss.
Whether or not hydrangeas need protection depends on how cold the winter temperatures drop. If the air temperature doesn't go below 0 degrees (zone 7) there is no need for winter protection. In colder climates, wrap or completely cover marginally hardy hydrangeas.
During the winter, make a DIY A-frame wire cage out of burlap and chicken wire to protect your hydrangea plant. This cage will protect it from winter winds, heavy snowfall, and cold temperatures.
The hardiness zones for H. macrophylla are 6 to 9. Effectively, a hydrangea should be able to sustain a temperature of minus-10 degrees. But in the real world, temperatures as low as 12 degrees — and late fall or early spring freezes — may reduce the flowering capability of this hydrangea.
Some varieties, like smooth hydrangea (“Annabelle”) and panicle, or PG hydrangea, 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 hydrangea. They don't need protection unless the temperature dips below negative 30 degrees F.
The Bottom Line. If extreme cold weather has damaged your Hydrangeas, they will most likely recover. These plants are hardy, and though they may not rebloom this year, as long as you prune back the damage done, you should start to see its beautiful flowers the following spring.
However, stop deadheading hydrangea shrubs in mid to late fall, leaving any spent blooms in place. This not only provides winter interest, but also ensures you don't remove the buds that will become flowers next spring.
But when to prune them? Prune fall blooming hydrangeas, or old wood bloomers, after they bloom in the summer. If you prune old wooded hydrangeas in fall, you are cutting off next seasons blooms. Summer blooming hydrangeas, or those that bloom on new wood, are pruned in the fall, after they stop blooming.
Big Leaf Hydrangeas, Hydrangea maculata, do not tolerate frosts well and should be covered to prevent leaf damage and flower loss.
Covering should be done when fully dormant (around November 30th), or at the same time you would cover perennials in your garden. In spring, uncover with your perennials when the ground is no longer frozen.
Hydrangeas don't look very nice in the winter. And they look even worse in the Spring! The old branches look dead at the end of winter (even though they're almost always just dormant); and they are unattractive for a while.
Foliage that has been frost damaged will turn purple/reddish. It may wilt or collapse. In a freeze, the stems, buds and foliage can turn black and dry looking. If you have experienced a frost or unexpected late freeze after your hydrangea have put on fresh new growth, it should be obvious that this is the problem.
Without going through the deadheading process, hydrangeas will not produce as many flowers and the few produced may not grow as big to their full potential.
While some plants bloom on new growth, others primarily set flower buds on old wood. Regardless, it is best to wait to prune all hydrangeas until spring. In the fall, hydrangeas (and all trees and shrubs) are in the process of going dormant. They do not produce very much new growth until the following spring.
The primary reasons hydrangeas don't bloom are incorrect pruning, bud damage due to winter and/or early spring weather, location and too much fertilizer. Hydrangea varieties can be of the type that blooms on old wood, new wood or both. Old wood is the current year's growth and new wood is next year's (spring) growth.
Absolutely! Hydrangeas are hardy shrubs that can survive a winter freeze. As long as the shrub isn't subjected to repeated below zero temperatures, most species of hydrangea will be just fine through colder weather.
5. Bring potted hydrangeas inside. Potted hydrangeas overwinter best in a garage or basement where the temperature stays cool but doesn't freeze. The plants will go dormant, but you'll still need to water the pots occasionally, about once a month, to keep the roots moist, until spring.