Trim old stems to a max height of 24" in spring when they're starting to leaf out. Under those conditions, the support you've already provided should be adequate.

A friend of mine uses a stake and fishing wire system. Her annabelles are typically 5 ft tall every year based on her pruning height (which I cant remember what that was) and form a hedge of five each. She uses stakes that are roughly 3.5 - 4ft out of the ground. Think they may be in the ground a foot or more, to keep from tipping over. She stakes them every few feet along the front and back of the hedge to form a frame. Then she takes heavy gauge fishing wire and wraps it around each stake, going from stake to stake. Once she is done with a row, she secures it tightly and does another row. Think she has 6 or 7 rows of wire supporting the hedge. When you place the stakes you dont want to do it too close to the plant, but not to far eaither. Too close and the flowers will still have a decent floop. Too far and the stake system will be visable and possibly miss mainy of the flowers.

The problem with this method is its best to do it in spring before everything starts blooming. Suppose if you did it carefully you could do it now without damaging the plant. Plus it would give you an idea of where the stakes would need to be next year. Her system works great. Hope this helps some. Good luck.

I just went to Wall-mart or Home Depot (can't remember which) and bought that standard green wire "fence" -- about 3 ft. tall--that you just stick in the ground. I wrapped that around my Annabelles. That was 2 years ago. My two Annabelles have stayed erect (more or less) as that time.

It was a bit of a wresting match--one person holding back Annabelle's branches AND at the same time inserting the "fence" in close enough to support the hydrangea's canes. On the other hand, you want the fence out far enough so that if some of the canes want to lean over, they will "rest" their big heads on the fence and therefore go no lower than 3 ft.

Kate

Good stakes for larger plants can include rebar, angle-iron, or a metal fencepost (for wire fences).

You can buy those green stakes (or bamboo) at Walmart, Home Depot, Lowe's in various lengths from probably 2' up to 8' (and the taller they are, the thicker they are). There are many types of ties as well in that section - twine, tape (not sticky tape but green vinyl 1/4" wide tape, twist ties, plastic covered wire, etc,) Usually two 5 foot stakes and some twine is all you need to tie up floppy, droopy hydrangeas but you can use more if you wish. I bought a lot of them last year for using on tall begonias, lilies, and some hydrangeas. Use twine to time up many limbs though.

Here is an example of a 4 foot stake in a begonia pot with a twist tie (you can buy a spool of it that includes a cutter). I cropped into a small section of the full photo.

Thanks for the suggestions, everyone!