I've grown thousands of duetzia in the past from cuttings, and have purchased many more than that from other sources, and have not seen a grafted one. But that was a few years ago, and there have been many new introductions since then.

So many more plants are being grafted (commercially) than in the past, so who knows?? ;-) What is the deutzia species?

It would be to your plant's advantage to keep the root stock shoots clipped away religiously. H. paniculata is a vigorous grower, and if used as root stock for some reason, might have a tendency to overwhelm the scion material.

thanks for the response. the cultivar is '"magician'.

Hmmm, I was hoping that knowing the variety might lead to an answer to your mystery, but it doesn't. I see no reason why a hybrid like 'Magician' would be grafted to hydrangea root stock.