Hydrangeas — to prune or not to prune?

By Lynette L. Walther | Oct 06, 2016
Photo by: Lynette L. Walther The double-flowered Cityline Venice and dainty Blushing Bride bigleaf hydrangeas are just two examples of the vast selection of hydrangeas available now.

The hydrangeas have been glorious this summer in spite of the dry weather. Just when the daylilies and coneflowers commenced their summer songs, they were backed up by the luxuriant chorus of clouds of hydrangeas. Long-blooming and long on impact, hydrangeas clearly are a garden must-have. But now, as the season is winding down, we prepare our gardens and the hydrangeas, for winter’s slumber.

Hydrangeas have undergone a magnificent transformation in recent years as hybridizers have developed hardier, more dependable varieties with awe-inspiring blooms in vibrant hues. There are even petite hydrangeas for small gardens and tight spots.

A problem for many gardeners is that all those varieties available now can make it confusing when it comes time to clean up the garden at the end of the season. We prize our hydrangeas for their beautiful flowers. We also want to make sure to prune them at the right time to encourage the stunning blooms every season. With all the new choices available now, many gardeners wonder when to prune them, or if they need to be pruned at all. Some hydrangeas bloom better if pruned, others not.

“The first step is to determine the variety of your hydrangea,” said Tim Wood, new product manager at Proven Winners ColorChoice. “This is fairly easy to do. If your plant produces big pink or blue flowers, it is a Hydrangea macrophylla. If its flowers are round and white — or pink, in the case of the new Invincibelle Spirit — the plant is a Hydrangea arborescens. Finally, if the plant has large, conical flowers, which are often white, but may also be green or pink, you own a Hydrangea paniculata.”

Here’s how Wood suggests you care for your hydrangea:

Bigleaf hydrangeas: If you have Hydrangea macrophylla, also known as bigleaf hydrangea, Wood says you can relax. This plant requires little more than a trimming and only immediately after flowering. You should never prune it in winter or spring, because it sets flower buds the year before and if you shear it back, then you will cut off all of summer’s flowers.

Newer reblooming varieties, such as the Let’s Dance series from Proven Winners ColorChoice, will also bloom on the current season’s growth, but you still want to leave the plant intact through spring so you can enjoy early summer flowers.

Smooth hydrangeas: Hydrangea arborescens, also known as smooth hydrangea, are adaptable and provide reliable blooms. Prune this variety back in late winter or early spring. These hydrangeas bloom on “new wood” — the current season’s growth. Pruning them back at that time encourages new growth, which produces flowers. Spring pruning will also result in a fuller, stronger plant that’s less likely to flop under the weight of its abundant summer flowers. Cutting the stems back to one or two feet will leave a good framework to support the blooms.

Today, there are two new “Annabelle” Hydrangea arborescens with stronger stems, so they won’t flop after being established. Invincibelle Spirit Hydrangea is the very first pink-flowered form of “Annabelle.” Invincibelle Spirit continues to produce new pink flowers right up until frost, providing a beautiful display across several seasons in your garden, from mid-summer to fall. Incrediball Hydrangea has the biggest flowers and the strongest stems of any of the “Annabelle” hydrangeas. Incrediball produces incredibly large white blooms as big as a basketball.

Hardy hydrangeas: Hydrangea paniculata, sometimes called hardy hydrangea, also blooms on new wood. Prune back in late winter or early spring. It can be cut back to the ground or, for slightly taller plants, cut it back to one to three feet. This is a great job for one of those early spring days when everything is still dormant, but it’s so beautiful and warm you need to be in the garden.

A new variety of Hydrangea paniculata won’t require as much pruning to keep it smaller. The new Little Lime Hydrangea boasts the same colors and benefits of the famous 'Limelight' Hydrangea, though only reaching three to five feet fully grown. At one-third the size of other hardy hydrangeas, it fits well into practically any landscape. Little Lime produces bright, cone-shaped lime-green flowers, later turning into pink, from mid-summer to frost.

Fortunately, even if you make a mistake and prune at the wrong time of year, these plants will forgive you, Wood adds. You may not have flowers for a season, but, with proper timing, you’ll see them the following year. Just remember to start by correctly identifying which kind of hydrangea you have. With just a little work, you’ll get beautiful flowers from your hydrangeas year after year.

And for hydrangea care for the winter:

Mulch with a two- to three-inch layer of well-rotted compost over entire root zone, which will give the plant a jumpstart in the spring

Water until the ground freezes, especially when establishing new hydrangeas, and as needed to supplement rainfall.

Wait to prune (see above for variety pruning suggestions) until early spring when new foliage begins to emerge to avoid trimming too much.

For varieties that require some winter protection, provide a physical barrier such as a burlap-wrapped frame, filled with shredded leaves. Remove in early spring and check from time to time to avoid pest damage to crown of plant.

Bigleaf hydrangeas like this stunning lacecap bloom on both new and old wood. (Photo by: Lynette L. Walther)
Clouds of soft pink blooms cover the Invincibelle Spirit hydrangea right up until frost. This smooth hydrangea blooms on new wood. (Photo by: Lynette L. Walther)
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