COLUMN: Hydrangeas— Pruning key to beautiful blooms

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Hydrangeas are prized for their beautiful flowers. To make sure you get those blooms, it is critical that you know when to prune them. It all depends on the type of hydrangea you have.

Hydrangea paniculata (Woody Hydrangea)

These are large shrubs or tree forms; you’ll typically find them blooming towards the end of the summer in old homesteads. They are normally white, with cone-shaped flowers that are blush pink to salmon, as nights turn cooler in the fall.

This variety blooms on new wood and should be pruned back in late winter or early spring. You can cut them back to the ground, or, if you want taller plants, cut them back to one to three feet. Cultivars include: Limelight, Little Lamb, Pinky Winky, and Quick Fire.

Hydrangea arborescens (Smooth Hydrangea)

This is a large plant with white snowball-shaped flowers. It is the most cold hardy of all hydrangeas. These varieties are fearless; they will bloom even with severe winters and severe pruning. It blooms on new wood, the current season’s growth; pruning in late winter or early spring will encourage the new growth which will produce flowers.

Cutting the stems back one to two feet in the spring will also result in a fuller, stronger plant that is less likely to flop under the weight of the flowers (a typical issue with this variety). More popular cultivars include: Annabelle, Invicibelle Spirit, Incrediball, and Bella Anna; some newer introductions have pink flowers.

Hydrangea macrophylla (Mophead Hydrangea)

This is the variety with the blue flowers. Different cultivars also include pink, purple and white flowers. This is the type of hydrangea that causes the most pruning problems. This plant requires little more than a trimming, and only immediately after flowering. If you miss your opportunity to prune, you need to wait until the following season, or you risk cutting off all the season’s flowers. Once the bud cycle is broken, there is nothing you can do to get it to flower for that season. No amount of fertilizer will change that; you will just see lush foliage. More popular cultivars include: The Let’s Dance series, Cityline, and Abracadabra series.

Some of the newer varieties of macrophylla are being bred to bloom on both old and new wood. A lot of this breeding is because of the pruning issue. Here is a special note if you purchased or received a hydrangea for a special occasion such as Easter. Many greenhouse varieties are likely not “bud hardy” for our area. They have a good root system and may come back to grow into green bushes, but because they are not bud hardy, you may never see a bloom again.

Do not let this confusion with pruning scare you off hydrangeas. They are stunning plants; plant breeders are starting to develop shorter and more compact varieties that can fit into any size landscape. Many are now bred to bloom on both old and new wood, making pruning mistakes more forgiving. The most important thing is to select your plants carefully, using reliable, local plant nurseries. The staff will know our area, be able to recommend the best variety for your landscape, and give you the pruning information to keep your hydrangea blooming every year.

Keep the plant tag so that down the road, if there is ever a problem, you will be able to identify which hydrangea you bought. Remember, if you make a mistake and prune at the wrong time, all is not lost; your plants will forgive you. You may not have flowers for a season, but with proper timing, you will see stunning blooms the next season. Happy gardening!

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