To prepare hydrangeas for winter in colder areas, add a thick layer of mulch around the base of the plants to protect the crown and roots from freezing temperatures.
Hydrangeas that bloom on new wood can be safely pruned in late fall once the plants have gone dormant or in early spring. Next year's flower buds won't be formed until late spring the same year they bloom, so there is no risk of removing the buds if you prune in fall or spring.
The simplest method is to mound shredded leaves or bark mulch around the base of the plant to about 12 inches or so. Put the mulch mound in place in late fall after the ground freezes, and uncover plants in spring when temperatures begin to stay above freezing.
To reduce the size of a hydrangea that blooms on new wood, cut off about one-third of each stem in late fall or early spring before it begins to leaf out. If your hydrangea blooms on old wood, prune right after it has bloomed when the flowers are fading.
To rejuvenate the hydrangea, remove up to 1/3 of the older living stems down to the ground each summer. This will revitalize the plant. If necessary to control the size of the plant, cut back before late July to allow for buds to develop. Usually the plant will return immediately to its former size.
Hydrangeas that bloom on new wood require pruning in late winter or early spring. Prune to shape, cutting back to about two feet. The pruning promotes new, sturdy growth, which provides the blooms next season.
Cut the dead stumps down to their base to completely remove them. This will allow the new growth underneath to have a chance to succeed. Dead and old blooms need to be removed to make room for new buds to come through. Cut the flower head off right above the first few leaves to encourage blooms for the next summer.
Big Leaf Hydrangeas, Hydrangea maculata, do not tolerate frosts well and should be covered to prevent leaf damage and flower loss.
Bottom-line: Panicle-type hydrangeas should be pruned in late winter or early spring. While they could be pruned in fall, we highly advise waiting until late winter/early spring to reduce risk of injury.
When to prune hydrangeas. Most pruning is carried out in late winter or early spring. However, the climbing hydrangea is pruned after flowering in summer.
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.
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.
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This is an all-purpose blossom booster that's suitable for use on a wide variety of perennial and annual blooming plants, including hydrangeas. It provides various minerals, including copper, calcium, and iron, to supplement common nutrient deficiencies.
For best results when planting hydrangeas, follow these steps: Create a hole twice as wide as the plant's root system, and about six inches deeper than the plant's pot. Break up the soil a bit before you plant to help the roots easily establish themselves.
Some gardeners report success in turning their hydrangeas blue by applying coffee grounds to the soil. The coffee grounds make the soil more acidic, allowing the hydrangea to more easily absorb aluminum. In addition, fruit peels, lawn clippings, peat moss and pine needles, are thought to have a similar effect.
When you deadhead hydrangeas, you aren't harming the plants at all. Removing the spent blooms triggers flowering shrubs to stop producing seeds and instead put their energy toward root and foliage development. This makes plants stronger and healthier, so by deadheading, you'll be doing your hydrangeas a favor.
But if you do choose to prune one, remember this: Time it based on whether the type of hydrangea you have blooms on old wood or on new wood. If it blooms on old wood (stems from the summer before the current one), its buds are being formed, and if you wait too late you may cut them off, meaning no flowers next spring.
Some introductions such as the Forever and Ever series or the well known Endless Summer family bloom both on old wood and new wood. The spring flowers occur on the prior year's old wood, while the fall flowers occur on the plant's current-season new-wood growth.
Check your plant when it's blooming; you should be able to see and feel a bit of difference between old wood and new wood. Old wood should be stiffer, tougher, thicker, and more grey or brown, while new wood will be much more flexible, soft, and should still have a greenish tinge.
As long as you have chosen a variety that is suitable for the hardiness zone you are growing in, your hydrangeas can survive a cold winter. If they get damaged, either the buds or the branches, there are ways to remedy the damage. If you are concerned about frost damage, protection is your best bet.
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.