Not usually in the garden. It can pop up on occasion with stressed out nursery stock. I say go for it if you have the room.

Not much experience here for Ninebarks, but I've had one for two years with no mildew problems. I had to move it once because the deer liked it.
Mike

Great, thank you! Very few deer in Portland suburbia, so it will be safe.

I have three a mix of Center Glow and Coppertina, two of them do fine, one of them gets powdery mildew. What is different about the one that gets it is it doesn't get a lot of water, it is on my drip system but the flow is lower there on that line. I'm in Seattle/Portland area. So as long as good amount of water in summer for it I think you're okay.

I also have Coppertina and Centerglow (about a half dozen) and no problems whatsoever with PM

Transplanted as rooted cuttings this spring & all are doing well. One is even in a saucer awaiting transplanting after the backhoe passes through the side yard one more time...

No PM even when I've neglected to keep the soil moist. Area was previously blueberries, diseased cherry tree, weedy, so spread cardboard & mulch. Then after a month planted right through it all then mulch replaced.

I have not seen any sign of PM on any of my 4 Diablo Ninebarks even in this drier than usual summer. In fact, I have seen nothing that hurts these, even the gophers leave it alone.

Thanks, everyone! Now to just find one.