Posted: 06/04/2013 at 16:47
It is now reckoned that there is only one spcies, H. nobilis. So all those Japanese ones are just as hardy in theory as the others.
None of them are that difficult to grow, just needing woodland soil and light shade. The ones I have are just appearing from under a foot of frrozen snow and look no different than they did last year.
Seed is best sown while still green and needs to be kept moist at all times, Needs no heat to germinate. Sometimes it does so immediately, at other times in Spring. If you do get them to grow then do not prick out until the plants have really got going, possibly in the second or even third year.