I don't know exactly what happened to her Cotinus. If helps here's a pic of ours right now... I had pruned out the largest stem to the ground early spring as suggested by the nursery when I purchased it last fall at 80% off in good health in a 20 gal pot. The part I cut was 1 1/2 thick" & 3' tall. The remaining part was only 1/2" thick, so younger growth & I decided to leave it. I planted the bed quite dense with perennials & also included annuals like snapdragons, lunaria, & bachelor buttons. I won't need those next year. My notes on the smoke bush (don't remember from whom): To get the best foliage color out of a purple-leaved smokebush. Early each spring, cut the shrub back to within a foot of the ground. The technique -- called stooling -- may seem drastic, but the payoff is nearly immediate: lush and large-leaved four-foot pillars of deep wine reds or chocolate purples, depending on the cultivar you buy. Of course, if you do whack back the shrub, forget about the smoke. By removing the current season's woody growth, you've nuked the flowers (and therefore the silklike hairs on the spent floral plumes that give the plant its common name). For a smoking bush, just let it grow. And, might I add, grow. The shrub resents pruning (as opposed to stooling) and will develop gangly, whiplike stems to spite you if you try to keep it small. Coppicing or partial coppicing yields a fresh, graceful, manageable plant, while heading back the entire plant partway will produce a congested mass. Here is a link that might be useful: pruning guide

Thanks for all the comments and suggestions. I actually have a Blue Surprise which I love but it is sooo slow. Would love to have that in just a little larger version. Also have a Barry's Silver which I may move to that position to see how it sits with the Cotinus. Ogcon, I too cut my Cotinus back every year. Could care less about the smoky "flowers' , I'm after the foliage. I set mine so they would get back-lit and side-lit by the sun - just lovely. Love the Ellwood's Piller if I could be sure it would get taller. Checked out the Cham.lawsoniana 'Wissels Saguaro; ehm...don't think so. Picea pungens 'Fastigata' - yep too coarse for what I'm after Ken, I've read warnings about tip blight w/junipers but I don't know it it is "an issue" up here or just a caution. Went to Portland nursery to look at the J. skyrockets they had there - close up they looked different from the online photos. I think I prefer the texture of the Blue Surprise and well...it is such a lovely color. Monrovia has the The Guardianî Series Disease-resistant Chamaecyparis. Here is a link that might be useful: Monrovia's The Guardian® Series Disease-resistant Chamaecyparis.

I am a wee bit confused by the zone 4 by your name but zone 5 in the text, but I wanted to add that around here on the border of zone 4 and 5, ma nature often does the coppicing of purple smokebushes which don't seem quite as hardy as the old-fashioned ones I see by farmhouses in large sizes with the smoky blooms. There are a couple of purple ones I see regularly that are more than 15 years old which are often killed back to the snow line, so I am glad that you are planning to grow them that way.

Cotinus are prone to verticillium wilt and I have seen that pathogen take out a number of them.......somewhat similar to the way you described. The plants were typically subjected to some sort of stress that allowed infection....like drought, although it usually doesn't happen quite that rapidly. I would suggest you wait to see what happens. Often with VW, the leaves will persist on the branches indefinitely, even though dried up and dead, so that could be an indication.