I did it that way too. As long as you keep them watered and fed through the summer (probably better than a store would do, anyway) you're in good shape. And the plants prefer the cooler air (less stressful.) Thanks for your comment.
works up here as well. I bought three heuchera that looked mostly dead but were viable at the base of the plant. I planted them, watered them (not too much) and now, three years later have huge lovely healthy plants that would have cost 10 times as much in the spring. Thanks for reminding people to shop in the fall just as eagerly as in the spring.