Well, Christine, we grow lots of cannas here at the farm, and you'd be surprised at the different varieties that are available for planting. There are dwarf ones, and there are some that grow very tall.
I grow cannas for a number of reasons. One is that they have beautiful blooms, but, more importantly, I think it's their foliage. There's so much variation in them, so they can work in a variety of situations.
It's important to note that cannas grow from a rhizome rather than a bulb, and you want to select rhizomes that are firm and crisp and have a prominent, bright eye. Since you live in Ohio, your cannas will have to be dug up in the fall and stored in a cool, dry place through the winter and then replanted in the summer. In southern parts of the country, they can be left in the ground, and they come up in big, large clumps year after year.
Christine, just remember, cannas like it hot and in the summer, they'll really show out in your garden. I hope I've answered your question. Good luck.