I wish I knew, Mary. The tops did not grow a "bit" in the fall. Depending on variety, most were 1'+ tall. When we really got cold (for us, teens and 20's) there was little noticeable growth and then in the spring, they took off again, some of it over well over 2' tall.
I think the snow actually insulated your bulbs from heavy freezes. I don't know how deep your soil freezes in the winter. Ours does not freeze at all. Even with teens and 20's, it just doesn't stay cold enough, long enough for our ground to freeze.
I plant mine approximately 2" deep as well. And I do mulch, but don't know that I really need to. I just try to cover all my bases when growing. I guess many folks would call it "over-kill".
