But one bit of caution. I've had a terrible problem with dieback from root rot this year because of all the rain. My clay soil just does not drain well enough. The bigger plants/deeper roots are worse off than the smaller ones. This is the first time I've had any problems whatsoever with my rugosas--they've even survived the RRD that plowed thru here a few years ago. So give them a deep hole with lots of sand. Rugosas are originally from the northern coasts of China and Japan, which is why they do so well in New England and the Maritimes. And they did well for me in Santa Fe. But they don't like wet clay!

A caution about adding sand to clay, however--you need at least 70% sand before the mixture begins to lighten and drain better--and even then, where's the water going to go? Planting your rugosas on mounds might be helpful.

Michael is right about sand. I have dug a very deep hole, put a few inches of gravel on the bottom, then sandy&gravel, then sand&soil, the sandy soil . That works pretty well because the feeder roots will often shoot off to the side, but the main root doesn't sit in a puddle. But its a lot of work and mostly I am too lazy--and then pay for my laziness when we get a rainy season.