This is my fault. I have read in several sources that Cotinus coggygria needs two cutbacks -- the first in late winter when it should be cut to the ground, and then after it leafs out in May, it needs a reduction shearing to keep the upward reaching branches vertical and graceful as it grows later in summer.
I know this. But I didn't do it. You see the ungainly results.
By cutting it back in May, you get the smaller, slender upright branching that I have seen in other gardens, notably at Chanticleer, where low, vertically branched smokebushes surround the parking lot like a ring of fire.
Or at Berkshire Botanical Garden, where the deep red stems are small enough to fit in the flower border, making a nice upright accent.
Here's what Louis Raymond (of The Plant Geek) says about smokebush:
Resist the urge to pinch branches if they have become overly-long stems; the resultant high-altitude side-branching will only look clunky. Instead, next year try being proactive.
If you pinch new smokebush stems in late May -- or whenever they are still less than a foot high), you'll achieve denser and, overall, less floppy and bulky growth.
And you'd still retain the interesting thrusting verticality of its new stems, which have a casual but organ-pipe-like effect.
I did cut back all the stems in winter, leaving about a two foot stem structure. But then I just let it go, and never did anything else.
By early June it was already too late to make the second cut back.
At a garden tour in Peterborough, New Hampshire in August I talked with Michael Gordon (of The Gardener's Eye), and he said he does the two step cutback with his 'Grace' smokebush, which was small and in fact had the delightfully described organ-pipe effect, tucked into borders in his garden.
He cuts his all the way to the ground, rather than leaving a two foot high trunk structure.
I have read this advice in other places too, and I knew about it before this season, but didn't do anything and the result is an awkward big shrub that is the focal point coming up our driveway.
Rather than the organ pipe effect of small upright branches, what I was really going for with my smokebush was the billowy shape of this one, seen at a neighbor's garden several years ago. You can tell it has not been cut back at all since it's covered in airy flowers, which you would sacrifice if the shrub is cut back to the ground.
But leaving mine unchopped did not result in this pretty form. And cutting it back in winter without a subsequent May reduction hasn't been working either.
So next winter I'll cut this all the way to the ground -- not leaving the two foot high skeleton as I have in the past. And I'll remember to do the second cutback too. Let's see if I get anything close to an organ pipe effect with that approach.