They both get about 7 by 7 give or take a foot either way. Hard prune them sometime between fall to early spring. They will defentily not reach 10 foot no matter what. Hard pruning will help you keep them under control, plus give you larger flowers. They should be ok in a 6 by 6 space if you hard prune.

How hard is "hard prune" on an hydrangea? On a rose, I would take that to mean pruning nearly to the ground.

Kate

My local nursery hard prunes down to one very strong stem (it's probably around 6" thick), and it shoots up to six or seven feet every year, with huge blossoms.

I want to make sure I'm understanding you correctly. Do you mean prune it back nearly to the ground--so that there is nothing there but one stem a few inches tall?

Don't mean to be dense. After a hard winter, I have had to prune hybrid tea roses down that low, but I was not aware that was ever done with hydrangeas. Don't want to chop down the hydrangea to a stub and then find out that was the wrong thing to do, if you know what I mean. LOL

Kate

We prune a limelight ever Spring to about 3' and 5 or 6 stems and it is 7' and loaded with huge flowers by July-Aug

I was until last year pruning mine like a regular shrub. Then last Spring I decided to prune down to around 2 foot and I could tell the difference immediately that year in the quality of flowers. Plus the vigor of the new growth. I can not say enough how much better the quality of flowers I received last year after pruning down to 2 feet. I was just to scared to prune down to a foot or less last year.

This year after seeing the difference of last I had the courage to prune down some to a foot or a little less and they are the same size as the ones that I cut down to only two feet again. So so far I am thinking if you cut down to a either 1 or 2 feet, seems like you will get a similiar result with a mature one. Pruning to the ground seems a little extreme, but wouldn't be surprised if it even works better. Because the really did respond well to the harder pruning.

These types of hydrangeas (Paniculata) play with completely different rules than others! Very easy to grow and reliable. You can prune smooth hydrangeas like the Annabelle in the same manner, because they both flower on new wood. Although Oakleafs and Traditional Hydrangeas most people think of like Nikkos (Macrophylla) bloom on old wood and should not be pruned in this manner. Although now they have came out with recently Macrophylla Hydrangeas that bloom on new and old wood, like the Endless Summer series of Hydrangeas. Hope I was helpful and did not ramble on too long. Good Luck!