I had been trying to figure out how to tackle #1 on my list for a while now, how and when to prune hydrangeas. Then the inevitable phone call came from an out of town friend, "we had a landscaper come clean up our yard, and he pruned the hydrangea down to about an inch off the ground, that's not what you are supposed to do right???" Um, nope...
Here's the thing, pruning hydrangeas is not that tricky, it's all about knowing when to do the job. In order to know this, you actually need to know what kind of hydrangea you have. Really people, you need to save those little tags that come on the plants somewhere in your garage or shed because the information that it has is really important. I'll try to make this as simple as possible.
If you've got Hydrangea macrophylla (the big mop head blue or pink flowers) there are two types it could be; Nikko Blue (probably what you have if it was planted more than 3 years ago) or Endless Summer (rebloomers, they keep blooming all season long). If you've got an Endless Summer, you are in luck, because you really can't screw it up. Best idea would be to prune now, or early next season and you should have plenty of flowers, because they bloom on new growth. If you've got a Nikko Blue it's a lot tougher, and you've already missed your window for this year. The only time to prune them is late summer, as they flower on the previous year's growth. Prune now and you can kiss next year's flowers goodbye!
If you've got a Hydrangea paniculata, (white flowers also, may be in tree form) it's easy as can be. Like the Endless Summer, it blooms on new growth so pruning now or any time in the late winter/early spring will do the trick. There are several other types of hydrangeas, but paniculata and macrophylla make up 95% of what I see in the suburban landscape.
Okay, so that covers the when. I'll tackle the how another day as it's going to require pictures or diagrams or something like that. That's going to take a little more organization on my part. Time to go dig out my notes from Hort school.