There seems to be a great deal of confusion regarding when to prune hydrangeas in milder climates, such as here in California.
Pruning Hydrangeas in Mild-Climate Zones
It's not such an easy answer, as pruning not only depends on which part of the county in which you live, but what type of hydrangea you have: mopheads, lace-caps, oakleafs, ever-blooming, climbing, or paniculata varieties.
Many gardeners in other parts of the country prune many of their hydrangeas in mid-summer, after the flowers have bloomed. This allows the cut stems plenty of time to produce next year's flower buds before winter hits. Here in California, however, winter doesn't really hit as hard and fall is actually the time when many of our hydrangeas are just hitting their stride, continuing to look beautiful through the end of the year.
Therein lies the problem. It's now November, and while your hydrangeas are still going strong, many of you have a nagging feeling that you've somehow made a huge mistake by not pruning them. And to make matters worse, many of you probably don't even know which type of hydrangea you have – further compounding the confusion. Well despair not! Here's an easy way to figure out not only what type of hydrangea you have but when, how and why to prune it.
First of all, you need to determine which type of hydrangea you have. Most hydrangeas fall into one of these three categories:
1. Hydrangeas that bloom on old wood ('old' being defined as growth from the previous year). These are typically summer blooming and include H. macrophylla (your grandmother's Mophead hydrangea) H. quercifolia (Oakleaf hydrangea) and H. serrata (Lacecap Hydrangea).
2. Hydrangeas that bloom on new wood from the current year. These are typically fall blooming and include Hydrangea paniculatas ('Limelight', 'Tardiva' or 'PeeGee'), Hydrangea arborescens ('Annabelle'), or Hydrangea anomala (Climbing Hydrangea).
3. Hydrangeas that are remontant, meaning they bloom on old or new wood. 'Endless Summer' and 'Blushing Bride' are a few trademarked varieties considered to be 'everblooming', which produce flowers regardless of when they're pruned.
I live in Northern California, and when it comes to pruning my own hydrangeas I definitely have a 'laissez-faire' attitude. Due to our mild climate, I've had the same great results whether I've pruned my category #1 hydrangeas as early as September or as late as January.
How do I prune them? Once the flowers start to look dried up and lose their color, prune them down to the first or second pair of swollen buds. Here in Northern California, this usually occurs in December.
Why do I prune them? Most people don't realize this, but pruning hydrangeas is NOT a required annual event, but an opportunity to tidy up your plant. If there's any dead or spindly stems, cut them down to the ground. If you're pruning the shrub to control its size, you've probably got it in the wrong place. Mature hydrangea shrubs don't really respond well to this type of severe pruning. Consider moving it to another location where it can grow to its desired size, and you'll make your pruning job a whole lot easier!
Another reason to prune, is that sometimes older shrubs can become misshapen or spindly, benefitting from periodic rejuvenation. This is done by removing a quarter to a third of the oldest canes each year, cutting each cane down to the base. This will cause healthy, vigorous new growth to emerge, and after a few years of this you'll end up with a lush, healthy shrub.
My hydrangeas that fall into Category #2 are pruned by 2/3 in the late Winter (usually March). You can cut these types of hydrangeas within a few inches of the ground, but by doing so you risk tall and spindly stems the next year that flop over with the weight of the heavy heads of flowers.
And if you have hydrangeas that fall into Category #3, consider yourself lucky! It doesn't really matter when you prune them (just as long as they don't have flowers on them – obviously!) as they'll send out new growth, with new buds that will bloom that same year.