How to Prune Different Kinds of Hydrangeas Timing is everything
By Marie Iannotti
Hydrangeas make beautiful focal points in the garden, and they generally require minimal care other than pruning. Although many hydrangeas have interesting foliage and bark, most are grown for their large, showy blossoms. If hydrangeas don’t bloom for a season, it is usually due to one of three reasons: It did not get enough sun, an early frost or cold spell killed the flowers buds, or it was pruned at the wrong time. Proper timing for pruning is the key to keeping hydrangeas flowering in a way that fulfills their promise, but how and when you prune them depends on which type you have. Many modern hydrangeas have been bred to solve the pruning problem by producing ongoing flower buds on both old wood grown the previous season and new growth produced in the current growing season, but for older types, it's critical to perform pruning duties at the right time.
When to Prune Hydrangeas
When to Prune Different Type of Hydrangeas
Category Blooms on Old or New Wood? Timing for Pruning
Bigleaf (Mophead) Hydrangea Old Immediately after flowers fade
Smooth Hydrangea New Late winter or early spring, before new growth starts
Peegee (Panicle) Hydrangea New Light pruning in late winter or early spring
Oak Leaf Hydrangea Old Summer, after flowers fade
Tea-of-Heaven Hydrangea Old Immediately after flowering
Climbing Hydrangea Old Winter or early spring, only when necessary to control size
Bigleaf Hydrangea (Hydrangea macrophylla)
The popular bigleaf hydrangea, also known as mophead or florist's hydrangea, is sometimes easy to recognize because it is the one whose flower color changes with the soil pH: blue in acid soil, pink in alkaline soil. There are also a few varieties that simply stay white, making it much harder to categorize the species from the appearance of the flowers. The leaves of H. macrophylla are coarsely serrated and glossy, dark green. This group also includes the lacecap hydrangeas, whose flowers look like a circle of unopened buds surrounded by open petals. The unopened buds are actually the fertile flowers with pollen, while the flashy outer petals are sterile and are there only to attract bees. This is true of most hydrangeas, so don’t become frustrated waiting for all the buds to open.
Bigleaf hydrangeas set their flower buds at the ends of the upright or lateral branches, from late summer to early fall. Pruning bigleaf hydrangea in the spring or even late fall, after the buds have been set, will remove the flower buds and any chance of getting flowers that season. Instead, bigleaf hydrangea should be pruned as soon as the flowers have faded.
Spent flowers can be trimmed away as they begin to fade to keep the plant looking tidy. When most of the flowers have faded, examine the plant for the new growth coming in from the base of the plant. Selectively prune out the dead and weaker stems, both old and new, using bypass pruners. Don’t prune out all the old wood, since this is what will keep flowering as the new growth matures. This kind of annual pruning will keep the shrub vigorous.
Bigleaf hydrangeas are the variety most susceptible to winter bud injury. If you live in an area with severe winters or your plant is exposed to winter winds, you might need to offer it some winter protection, to protect the flower buds. Tying the branches together and wrapping them with burlap isn’t pretty, but it can help the plants survive winter. Remove the burlap when the buds begin to swell.
Smooth Hydrangea (H. arborescens)
Smooth hydrangea, including the popular cultivar H. arborescens 'Grandiflora,' doesn't usually have any problems blooming, although the white flowers are not as showy as we normally expect from hydrangeas. This is a round shrub with leaves that are somewhat rounded with a pointed end, paler on the under surface than on the top. Hills-of-Snow does not usually have trouble blooming because its flowers are set only on new growth. This is a good thing because it is very susceptible to winter injury and is often killed back to the ground in colder regions. If winter injury is not that bad, you can prune slightly by removing some branches to the ground and cutting others back to shape the plant.
This shrub blooms on new, current-season wood. Pruning should be done in early spring to ensure plenty of new wood for flowers.
'Annabelle' is another very popular Hydrangea arborescens cultivar with conical flower heads that are considerably larger than 'Grandiflora.' Its leaves are fuzzy gray on the lower surface.
Oakleaf Hydrangeas (H. quercifolia)
It's probably not surprising that oakleaf hydrangea is easily recognized by its oakleaf-shaped foliage. Since its major attraction is the foliage, loss of bloom is less disappointing than in other varieties. Oakleaf hydrangea also blooms on old growth and should be pruned immediately it has finished flowering. If it has experienced winter dieback, prune the stems back to below the point of injury.
Peegee Hydrangea (H. paniculata "Grandiflora")
This is the most commonly grown hydrangea variety. Also known as panicle hydrangeas, peegees have massive snowball-shaped flower clusters in mid- to late-summer. The flowers start out white and slowly turn pink, drying and remaining on the plant long after the leaves have fallen. These are also the varieties you see trained into standards that look like small trees.
Peegees do not require hard pruning to the ground. New flower buds will be set on new spring growth. Some gentle pruning of individual stems in late winter or early spring will not only keep the plants from becoming overgrown but will also encourage more new growth and hopefully more flower buds.
During the growing season, you can deadhead the flowers and clean up the overall shape of the plant as soon as the flowers become unattractive.
Mountain Hydrangea (H. serrata)
Mountain hydrangea, also known as tea of heaven, is a small shrub with narrow, pointed leaves and flattened flower heads. It is sometimes confused with Hydrangea macrophylla because the flowers can look like lacecaps and/or be blue or pink, but this type does not have the big leaves of H. macrophylla. Bloom occurs on old wood, and pruning needs are minimal. Prune after flowering, trimming back flowering stems to a pair of healthy buds. In early spring, prune out weak or damaged stems to ground level.
The stunning climbing hydrangea is the type you see slowly making its way up a tree or support. It is a vine, not a shrub, and it requires little to no pruning. Once climbing hydrangeas become established, they can grow quite vigorously and may need occasional late winter pruning to set boundaries for the coming season. Badly neglected, overgrown vines can be cut back to the ground level in early spring to rejuvenate the plant. This plant flowers on old wood grown the previous season.
Tips for Pruning Hydrangeas
■ Always remove dead or damaged stems as the first step during routine pruning.
■ When shortening stems, cut back to just above a pair of healthy buds
■ Winter damaged stems can routinely be cut back to living wood; the shrubs rarely die.
■ In general, varieties that bloom on old wood should be pruned immediately after they flower; those that bloom on new wood should be pruned before new growth begins in spring.
taken from https://www.thespruce.com/when-to-prune-hydrangeas-
till next time this is Becky Litterer, Becky's Greenhouse Dougherty Iowa firstname.lastname@example.org