Generally, in zones cooler than zone 8, you need to either treat gladiolus as an annual, or dig the bulbs each fall and store in dry sawdust or shredded newspaper in a cool, dark place. Replant in the spring.

I did have success planting them deeper than recommended and mulching heavily over the winter with shredded leaves. Not only were they sturdier and needed less staking, but they returned the following two years. I will be watching to see if they continue to return in the future, too!