Try the doubles. They do not seed. I have been lucky with a couple of seedlings that have been respectively good and excellent. I grow a group of 20 or so with space between for other perennials....I.e. dicentras, astilbes, Astrantias, aconitums. Agastaches, perennial salvias, Acteas, etc. ......and bulbs like daffodils and lilies. I guess I allow 3 or 4 feet apart. Floweriing clumps are quite big but when the spent flowers are removed in late spring they form nice evergreen mounds to offset other plants. Quite a low maintenance system too. But, what a glorious show hellebore orientalis provide.