Got a picture? I've heard Merritt can be trained into a tree but I've not seen many examples.

Anyhow, you could hope that the plant sprouts shoots from the base, and then lop the whole trunk off. Or you could root softwood cuttings from current year's growth by sticking an 8" long section of stem 2-3" into a pot of moist soil in shade with a set of 2 leaves cut in half. Either way, you would be starting over. You can't really "back-train" a tree into a shrub.

I don't have a picture right now, but I'll take a look at it during daylight hours and see if I can take a cutting and start a new shrub from it. The tree has been so top-heavy lately that it's been basically falling over onto the ground. I thought it might be due to the extreme heat, but I think it may need staked to stay up. I really wanted a shrub when I bought this tree but was hoping possibly that I could keep taking off the top so it would grow down below.

Thank you so much for your helpful information. What you say makes good sense to me.

Are you certain you have the right name for the plant you want to address? Hydrangea macrophylla Merritts Supreme is normally somewhat compact and dense, topping out to within approx 4 tall x 4 wide when mature. It's often listed with the semi-dwarf hydrangeas, and few macrophylla lend themselves to tree shaped....Photo if you could?

Check out this pic from Mike Dirr's website. Does it look anything like this?

{{gwi:1014214}}

Either it's possible or it's all just a big illusion!

I see....trained to a standard. Not my favorite form for many plants, having argued with a wisteria pruned that way for years...and I mean high maintenance there :)

That hydrangea in the photo is clearly staked, supported.

Natureperson, when yours began leafing out this last Spring did you notice or have to remove any growth buds along that single main stem if your own hydrangea looks like the above?