No expert here but can you identify a leader? At this point I would either replace it or try to trim it as you think you would like it. I don't think you can do more damage. Perhaps try to encourage some side growth

Hope you can read this

What I'm getting from it is that it can be grown more as a tree or as a shrub, so maybe it's okay that it has more than one main trunk.

Is it a smoke tree (Cotinus obovatus) or a smokebush (Cotinus coggygria)?

It's got plenty of room, why prune it?
Why not let it be all it can be?

Select landscape's question is crucial. A shrub is not a tree.

A shrub can be a tree and a tree can be a shrub. It's all in the pruning and sometimes the environment.
Mike

But....this is at best a smaller-growing tree. Such issues as developing a main central leader just do not matter much in this context. I see all those "competing" leaders are well-spaced and solid-looking. I'd probably just leave it be.

+oM

you need a single leader.. when young.. to grow a single trunk ...

once they get to a certain size.. is usually more of a problem for YOU ... rather than the tree ...

no matter how you try.. i doubt you will ever make it a single leader tree again .. and i say.. who cares ...

i would probably take off the lowest branches ... and work my way up .. over the next year or two ... to show off the bottom of the multiple leaders... and declare victory ... [which means.. in my garden.. just about everything that is showing retained leaves ... but not all at once ....]

the tree has no real problem... you do... if you insist on a single leader ... so the only question is .... why ...???

as john and paul said ... LET IT BE ... [as to making it a single leader plant]

ken

In searching on-line, there seems to be a tradition in some places of cutting smoke bushes back severely--termed "stooling". I'm not advocating that practice, but I do give my Continus 'Grace' a severe pruning every several years. I'll attach a picture below of what I've done this year. I'll also attach (or insert) an article I found http://thehort.org/blog/2007/09/best-time-to-prune-smokebush.html

The article refers to long whip like branches--I cut a few of these back every year just to control the size. You should also remember that it will bloom (produce smoke) on old wood. It also depends on which cultivar you have. Grace is a hybrid between the native obovatum and coggyria and will get bigger than straight cultivars of coggyria. If you have room, you don't need to cut it back at all, and I agree that you don't need to try to develop a leader. But I think you would have a more attractive plant if you cut the tall whips back by half right now.

Good luck, here is my picture, taken last week. I did the pruning in January.

Wow, thanks for all the responses everyone. To follow-up on a few. First, I believe it is a Smoke Tree (that's what I recall from when I bought it). And, it seems very happy growing like it is. I was just concerned that as a traditional tree, it needed one leader. I wasn't sure if it would be susceptible to splitting this way. But, based on the feedback, I'll let it go as is. Hopefully it will soon provide some shade from the morning sun that beats in the bay window of my family room! Thanks again everyone.

Whoa! Holy Smoke!
You REALLY cut back on it....too far in my opinion. You pruned it as if it was a Rose. It will sprout and grow very fast though, but I doubt you will have any 'smoke' this year.
Mine needs to be moved and I'm not looking forward to it in the next few days when it quits raining. I don't think this one will move too well. It's been there for at least ten years.
Last year I pruned it pretty hard down low, not so hard in the middle, and lightly on the top. This year I'm going to prune the top down a little bit. It will have more room in it's next location so the pruning regimen will be different than in the past.
I'm SE of Seattle, in the foothills.
Mike

RJ, it doesn't appear that the crotches formed by those multiple leaders are especially V-shaped, and as such, they look pretty sound and strong. That's the issue with, say, a young maple or elm, something that's going to get really large: You don't want to leave V-crotches, competing leaders, and such on those trees because, among other factors, the weight is going to be enormous and those types of structures like to split out in storms, etc. With your little smoke tree, just not a concern, just like it isn't with the flowering crab in my front yard. Sure, there's still some aspects of pruning that holds true across the gamut, but I think you're good here. Cool that you even know to be concerned with competing leaders, etc!

+oM

Smoke trees originated in a rather dry area. Their roots are narrow and long. They are tough plants! Nothing eats mine. No bugs, or animals.
In a garden setting, they grow uncharacteristically large and lush. It doesn't seem to hurt them though. I've never had a break due to snow or ice on one.
Yours looks good. I see no potential breaks.....now.
Keep us posted on how your Smokebush does.
Mike

miketann, I haven't cut it. I've had it I think 3 years. It was topped when I bought it. Last year it really took off and sprouted all those leaders. It has had lush dark red leaves and smoke every year though. It might look a little bare now, as we are just coming off of a winter with a few nice old spells here in St Louis.

Not a great pic, but it looked like this early last Fall.