"When to prune these woody-stemmed hydrangeas is not as critical as [with old wood] varieties, as long as you avoid pruning when the flower buds are opening," says Becker. Trim in early spring, before the flowers begin to bud, or after the plant has finished flowering.
Prune back stems to just above a fat bud — called a heading cut — in fall, late winter or spring. These plants have conical-shaped flower heads. I recommend leaving the dry, tan flower heads on the plant to provide some winter interest in your landscape, so I wait to prune these until late winter or spring.
The reason that climbing hydrangeas are pruned in summer is because the flowers are produced on the previous year's wood. If they are pruned earlier in spring, before flowering, the blooms for that year will be sacrificed.
Prune these hydrangeas only after bloom in the summer and not in the fall. Old wood hydrangeas start developing their bloom buds for next year in August and September. If you don't prune your hydrangeas real soon, then it is better to wait until next year. Otherwise you won't have any blooms next spring.
Cut back any clearly dead branches, which are brittle and snap off easily. This can be done in the fall or any time you see a dead branch. 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.
In late winter or early spring, these shrubs can be cut all the way back to the ground. Smooth hydrangeas will produce much larger blooms if pruned hard like this each year, but many gardeners opt for smaller blooms on sturdier stems.
Wrap with winter protection.
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.
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.
So these shrubs should be pruned immediately after their flowers fade. Conversely, if the shrub flowers on new wood (stems developed during the current season), its buds are set within the season, so the shrub should be pruned in early spring before that new growth emerges.
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.
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.
Cut back in early spring, pruning last year's growth back to a healthy framework that's between 30cm and 60cm high. Prune to just above a pair of healthy buds on each stem. Cut back to the lowest healthy buds for big flowers or less hard for a natural look or a taller plant.
Mophead hydrangeas look lovely in the fall when their blue, purple and pink flowers contrast with the fall foliage. Brown flowers can be snipped off if they annoy you, but you don't have to remove them. Look for flowers like this to dry or for making Hydrangea Wreaths.
Big Leaf Hydrangeas, Hydrangea maculata, do not tolerate frosts well and should be covered to prevent leaf damage and flower loss.
With their vibrant, plump blooms, hydrangeas offer a striking display in the warm weather - but what do they look like in the winter? As the delicate petals fade in the colder months, bright hydrangeas can quickly appear dry and brown - requiring targeted care to get them flowering again in April.
The lacecaps, similarly colored, are flattened corymbs with fertile flowers in the center surrounded by showy clusters of sepals of varying sizes. The hardiness zones for H. macrophylla are 6 to 9. Effectively, a hydrangea should be able to sustain a temperature of minus-10 degrees.
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.
Most common hydrangeas prefer a partial sun location - ideally receiving sun in the morning hours and shade in the afternoon. The reblooming Endless Summer® Hydrangea series prefers part shade.
Fall Bloomers
"Re-blooming varieties of Hydrangea macrophylla may produce some blooms into the fall," he adds. "Varieties like 'Seaside Serenade Newport' have flowers that can last for a couple of months—so they can continue to add beauty in autumn with their summer blossoms."