Sounds like an "Annabelle." The weight of the blooms make the stems flop to the ground. The tree type hydrangeas usually are "Pee Gees." Sorry, my mind is blanking on the latin names right now, but here is a sight for more info:

Here is a link that might be useful: hydrangea info.

That sounds just like the hydrangea we have that was here when we moved in. The green parts don't start until a few feet off the ground making it also look tree like, but it does not have as single trunk at the bottom. It must be over 8 feet tall and we pruned it a little last year because it seemed to grow so much over the summer (taking over the driveway that is beside it), but I would like for it to be a little shorter. I'm just a afraid that a severe pruning might damage it. I noticed this year that one branch of it from the ground up shows no signs of life, making one side of it look a little more bare than the rest.

My flowers also droop because they are heavier than the little stems they grow on, but it still looks quite pretty when in bloom. I think what I have is a result of little or no pruning so if the tree like look is what you want for the plant then I would say let it go and see what happens.

Sounds like a PeeGee (Hydrangea Paniculata Grandiflora). They can be large shrubs or trees depending on how you prune them. They bloom on new wood so unlike some other hydrangeas, they can be pruned as hard as necessary in late winter-early spring.....yg

Thanks. That's good to know. What exactly does blooming on "old wood" or "new wood" mean? I'm not really clear on that.

Hydrangeas that bloom on old wood, (most mopheads and lacecaps)set their flower buds the previous summer/fall and those buds have to survive the winter or the dreaded pruning shears in order to bloom the following summer. Hydrangeas that bloom on new wood (arborescens & paniculatas) set their buds on new spring growth and bloom in summer, therefore harsh winters, or pruning in fall, late winter or EARLY spring won't compromise this seasons potential blooms. In zone 4, only hydrangeas that bloom on new wood are viable. In zone 7 both types are very hardy as long as you understand the difference and treat each one accordingly......yg

Thanks for the explaination. I think it's clear now. Is it something you can discern by observing the plant or do you need to know what type it is to determine this. Just curious :)

Not exactly...

It helps to make the effort to study, at least a little bit, about the plants you want to grow, if you want to grow them successfully, or you will learn the hard way. (why isn't my hydrangea blooming? is probably the most common question) I prefer the former.

For a great tutorial on the basics about hydrangeas, go to hydrangeashydrangeas.com You are sure to be able to recognize the types you have and it can explain better than I can, almost everything you need to know......yg

Thanks! Very imformative website.

Yellowgirl has it correctly. Sounds like Hydrangea paniculata. Yes, it is best to prune it at the end of winter, early spring...in zone 7 that would be late Feb. to early May. Pruning hard to within 12" of the ground would create long whips with big blooms on the ends that would probably flop about. Whereas is you leave some woody stucture on the plant and prune more lightly it will create more numerous and smaller blooms that don't flop so much. There are many selections of Hydrangea paniculata, most have upright forms in the garden ('Tardiva', 'Floribunda') and 3 or more have weeping forms.....H.p. 'Grandaflora', H. p. ' Webb's form' (selected in Montgomery, Ala. and happier in the south than Pee Gee Hydrangea) and 'Limelight' seems to also have the weeping aspect. All get large, to 12 or 15' tall if left unpruned. Otherwise, expect 5' to 7' with creative, selective pruning. Great plants. Very forgiving. Always bloom no matter what unstable weather throws our way.

Anitamo, thanks for the link!
Now I know for sure that I have Anabelle's, something I have suspected for years!! Many years ago, a dear friend gave me a small "baby" that she called a "Snowball" bush. I planted it in a shady spot and over the years I kept it pruned to about 4 1/2 ft.tall X 5-6 ft. diam. It never failed to bloom! Well, last fall, my son was taking out some other shrubs for me and mistakenly cut down the "Snowball" bush! Thankfully, he didn't dig it up!! Now I have dozens of little "bushes" about a ft. tall. I plan to move some of them and share with friends! My question is: Can I plant some of them in a smaller space, and just contain their size by pruning? I am thinking this will work, since cutting them back to the ground seemed to do wonders!!
Thanks for all the help!