Based on the suggestions above, I shouldn't be able to grow any heuffelii! I'm so mean to all my plants, giving them very little water at any time, and putting them in the most horrible soil with no nutrition, but the key I think, is excellent fast drainage. If you have soil like mine which is awful, sandy, lots of rocks, then they should be fine. Of course, I can pretty much count on good snow cover, in fact, I woke up to another inch (where's the emoticon for 'groan!') Oh boy.
On a good note, and I'm glad that I did have great survival rates, I've got tons of orders for the heuffelii, even though they are seed grown, so not named varieties. I think people are finally taking notice of them, and want to try them, and this is a cheap (relatively speaking) way of doing it.
