Hydrangeas: When to Prune and How to Change Their Color

Macrophylla hydrangea--the most common type!

It's late summer, and despite all the other fun activities you’re trying to squeeze in before fall, now is the time to prune many varieties of hydrangeas around your yard. If you’ve ever struggled with getting your hydrangeas to bloom right—or even if you want to change the color of your blooms—here are some basic tips that can make your bushes look their best.

Hydrangeas come in many shapes, sizes and varieties, but for the most part, you’ll find four different types in garden centers and around your neighborhood—and knowing which type you have will determine when and how to prune.

First, macrophylla hydrangeas are the most common types. Whether you have the standard mophead (large, round flowers) or lacecap (very small blossoms surrounded by a ring of larger blooms on each flower head), prune them now! Macrophylla hydrangeas typically only bloom on old wood, meaning if you wait until next spring to prune your shrubs back, all the new growth they put out after their haircut will be nothing but leaves. Traditional mopheads and lacecaps should be pruned just as the blooms fade in summer so they have time yet before fall to develop flower buds for next year.

Paniculata hydrangea

The second most common hydrangea species is the paniculata family. You might know some of the common varieties like ‘Limelight,’ ‘Pee Gee’ or the newer ‘Bombshell,’ all of which are easily distinguishable by their cone-shaped flowers. Unlike macrophylla types, paniculatas can be pruned anytime between late summer and mid-spring, and may not even need regular pruning at all.

 A third common hydrangea species for our area is the arborescens type.  The most common of these varieties is ‘Annabelle,’ a white variety with large blooms, although others like ‘Invincibelle Spirit’—a  pink variety—are common, too. Like paniculatas, these hydrangeas can be pruned at any time other than late spring or summer.

The last main variety of hydrangea you’re likely to grow is quercifolia, more commonly known as oakleaf hydrangeas. They have cone-shaped flowers similar to paniculata types, but their leaf shape mimics that of an oak tree. Like macrophylla types, oakleaf hydrangeas should be pruned in late summer in order for them to bloom reliably the following year.

Now that you know the basic types of hydrangeas and when to prune each, let me offer this caveat: many of the new introductions in the last several years can be pruned just about any time of year, regardless of which species they are. So, if you’re in the market for a new hydrangea and want to keep things simple, ask at a garden center for some of the newer varieties! 

Finally, how can you change the color of your hydrangeas? In the Pacific Northwest, the acidity of our soil naturally turns macrophylla types blue over time. If you want to turn a hydrangea pink—or keep one that way—treat it with Bailey’s Color Me Pink™, a soil additive available at Vander Giessen's. Likewise, if you wish to intensify the shade of blue in your hydrangea, use Bailey’s Color Me Blue™.  Depending on your conditions and desired color, multiple applications of either product may be needed. For better or worse, the color of white varieties cannot be changed.

Hydrangeas are beautiful shrubs and easy to grow. With a little attention to what type you have in your yard, you can enjoy loads of flowers each year while also maintaining the size of your plants. And with a little extra care, you can even change the color of your blooms to suit your taste!