If there is one thing about trees and shrubs that scares people more than paying for them, it's when and how to prune them. One wrong move can ruin them forever (not really, but added anxiety makes for more attentive readers). But abandon all fear, young Skywalker. The Grump is here with easy guidelines for pruning hydrangeas that will make you so glad you turned on your computer
When to prune hydrangeas basically depends on whether it blooms on growth made last year or new growth made during the current year. So let's run down some of the most popular hydrangeas, so I can tell you what to do.
'Annabelle' hydrangea -- This is the showiest and most popular selection of the native smooth hydrangea (Hydrangea arborescens). It produces immense clusters (up to a foot across) of pure white flowers in summer on a shrub that grows about 4 feet tall and wide. It blooms on current season's growth, so prune it in late winter. Cutting it back to a foot tall produces fewer clusters, but they're huge (a trick I learned from Margaret Mosely in Decatur, Georgia). Cutting it back more modestly produces many more, but smaller clusters.
'Annabelle' smooth hydrangea
Panicle hydrangea (Hydrangea paniculata) -- This summer-flowering species likes the sun and is often trained into a tree 15 to 25-feet high. The most widely planted selection, 'Grandiflora' (often called "peegee"), bears large, rounded clusters of white blooms that age to to rose. I see it frequently planted in northern gardens as their version of crepe myrtle, which isn't winter-hardy there. Other worthy selections include 'Limelight' (lime green flowers that age to pink), 'Pink Diamond' (creamy flowers that age to rosy-red), and 'Tardiva' (late-opening, arrow-shaped clusters of white flowers that age to rose). Panicle hydrangea blooms on new growth, so prune it in late winter.
'Peegee' panicle hydrangea
Oakleaf hydrangea (Hydrangea quercifolia) -- This outstanding native native grows 6 to 8 feet tall and wide and develops striking burgundy-red fall foliage. Among the Grump's favorite selections are 'Snowflake' (inner florets stay white, outer florets turn rose in summer), 'Harmony' (huge clusters of double white flowers), and 'Pee Wee' (dwarf plant to 3 feet tall, blooms at a young age). Oakleaf hydrangea blooms on the previous year's growth, so cut it back (although it rarely needs it) in early summer.
'Snowflake' oakleaf hydrangea
French or bigleaf hydrangea (Hydrangea macrophylla) -- By far, the most popular of all hydrangeas for its showy, blue or pink, snowball-shaped summer blooms. Most selections, such as the standard blue, 'Nikko Blue,' bloom on last year's growth. So if you prune them now, you won't get any blooms. What you want to do is wait until they start leafing out in spring. You'll probably notice some stems are light brown with no signs of life. Prune them back to just above where you see fat, green buds starting to open. Most of these buds should produce flowers. Immediately after the flowers fade in summer, cut these stems back if you wish.
There are exceptions to these guidelines, however. Newer, repeat-blooming selections of French hydrangea, such 'Endless Summer,' 'Pennymac,' 'Mini Penny,' and 'Forever and Ever,' bloom on both last season's growth and current season's growth. You can cut them back in winter, spring, or summer and still get blooms.
'Mini Penny' French hydrangea
Mail-order source -- If you can't find these hydrangeas locally, one of the best mail-order sources is Wilkerson Mill Gardens, which specializes in these shrubs. I hope they don't mind that I ripped off the picture of peegee hydrangea from their website, but maybe if you order some of their stuff, they'll call off the corporate attorney.