When to Prune Your Hydrangeas

By Joanne K., Pitt County EMGV
Gorgeous hydrangea blooms in hues of pink, purple, blue, white, and green are the current stars of eastern NC gardens. These shrubs have really rebounded this year with robust blooms after the disappointing hydrangea displays in 2022 due to an exceptionally dry year.

But now as the blooms start to fade, gardeners are faced with the question of when to prune their plants.

Pruning is needed to remove old blooms, control size and shape, remove diseased/damaged stems and leaves, or rejuvenate an overgrown plant.

The rule of thumb for hydrangeas is if they bloom on old wood, cut back immediately after blooming, removing only about 1/3 of the plant. If they bloom on new wood, prune after flowering or in winter.

The challenge is to determine what kind of hydrangea you have.

Merritt's Supreme H. macrophylla

Commonly seen in local gardens are two types of hydrangeas: H. macrophylla -  Mophead or Bigleaf Hydran-gea, and H. macrophylla normalis - Lacecap Hydrangea.

Mopheads sport big round blooms in shades of pink, blue, and purple. Lacecaps, on the other hand, have a more delicate-looking flat bloom with a small inner ring of flowers surrounded by a ring of larger flowers.

Both are woody deciduous shrubs that bloom during the late spring and early summer on the previous year's growth ('old wood'). Their buds form in late summer to early fall, so prune them immediately after flowering. Pruning later risks losing next year's flowers.

Removing the dead flowers encourages leaf growth. Also, as your shrub ages, the recommendation is to remove 1/3 of the oldest stems by cutting them to the ground to let in more light and air.

Severely overgrown hydrangeas can be rejuvenated by hard renewal pruning, which cuts all of the branches to the ground. While you will lose next year's flowers, the following year's display should be good.

Also seen in local gardens is the southern native, Oakleaf hydrangea (H. quercifolia), with its huge oak-like leaves and white pyramidal flower heads. It also blooms on old wood. Prune after blooming if desired, but it isn't necessary. This hydrangea looks best when allowed to maintain its natural shape. Pruning may only be needed to cut out diseased or damaged stems or to allow more air circulation.

Oakleaf hydrangea H. quercifolia

Limelight H. paniculata

A current favorite hybrid hydrangea series, 'Limelight' and 'Little Lime' (H. paniculata), blooms on new growth with conical-shaped white flowers gradually turning green, then rose, and finally fading to beige. They can be pruned immediately after flowering, or you can enjoy the beautiful dry flower heads over winter, pruning them in late winter just as leaves start to appear and before the flower buds form.

"Everblooming" hydrangeas, such as Summer Crush ® Bigleaf Hydrangea and BloomStruck ® Bigleaf Hydrangea, flower on both old and new growth, and can be pruned at any time without losing flowers.

Other hydrangeas include the smooth (H. arborescens) and the climbing (H. anomala) varieties.

The smooth hydrangea, the most common native hydrangea in North Carolina, blooms on new growth. Prune it back to about 12 inches above the ground in late winter before spring growth for strong stem growth. Its cultivars include 'Annabelle,' 'Invincibelle Ruby,' and 'Invincibelle Spirit.'

The climbing hydrangea, with its fragrant white flowers, grows vigorously and should be pruned after blooming when the new growth has lengthened. It may only need pruning for shaping or to remove dead or diseased wood.

Hydrangea blooms are perfect for dry, indoor winter arrangements. An easy way to dry the blooms is to place the mature flowers with all of the leaves stripped from the stem in a container with a couple of inches of water. Keep the container out of direct sunlight.

In a couple of weeks, the process will be complete. The blooms won't absorb the water, and the dried color will be more vibrant than ones allowed to dry on the stem. Google "how to dry hydrangeas" for more information.

With careful plant selection, your garden can feature a beautiful continuous hydrangea display from late spring into the fall and winter!

Photos
'Merritt's Supreme Hydrangea,' H. macrophylla, Pink Bigleaf Hydrangea,
in the Wet Site Garden at the Pitt County Arboretum. Photo by Joanne K.

Oakleaf Hydrangea, H. quercifolia,
in row 2 of the Walking Trail at the Pitt County Arboretum. Photo by Joanne K.

'Limelight Hydrangea', H. paniculata,
in the Perennial Garden at the Pitt County Arboretum. Photo by Cindy C.