I've been growing Allium zebdanense here in Zone 5 (30 miles west of Chicago) in the shade garden for more than 10 years now. I do not mulch the area. During this period we've experienced low temps ( -28 F) with no discernible damage to the ever expanding clumps. I have noticed a minute amount of self-seeding. However, a friend in the same general area, has hundreds of these bulbs in her very humus-rich 5 acre shade garden where they self-sow with wild abandonment. Wish I could get mine to self-sow as much! I have also seen them thriving at Boerner Botanical Gardens, in Hales Corners, WI near Milwaukee. Betty Earl Naperville, IL USA Zone 5