DonnaMack wrote: Some alliums are weird. I planted a bunch of allium christophii one year and got nothing the next. So I put in more. The original ones seeded, and so did the next batch until.. they were everywhere (nice problem)!
But I put in alllium atropurpureum three times and they never came back. They were advertised to me as zone 5 hardy but I think that they were really zone 6.