Years ago I had some glads that came up without indoor winter storage for a number of years, and I am in zone 4 (sometimes seeming to verge on zone 3), but mine were planted right next to the house foundation. These gladiolus were nothing I cared about. I bought them from neighborhood kids who were selling them as part of a school project, and they were a mix of pastel colors that were never to my taste. They continued to come up each spring until we had earth dug up for our new foundation and addition about 15 years ago.

Gladiolus that I chose myself (in rich red and purple tones) I've taken better care of, and have dug the bulbs each fall. However, last year I planted a kiwi vine in the place where my glads reside, and, because I don't want to disturb its roots by digging out gladiola corms each year, I've made the conscious decision to just leave the glads in the ground. I expect they may survive, because they are next to the house foundation and should get some heat/protection from the elements. It will be interesting to see, but, for better or worse, they are on their own.

Zone 6 is considerably warmer than conditions where I live, so I'm not surprised that your gladiolus come up each Spring, Bill. I really love them, but they are a pain to dig up and replant each year. They also tend to flop over, but then they make very striking cut flowers for indoor vases.

I planted around a dozen about 5 yrs ago. Like Spedigree's, they are right up against my foundation. I'm in Zone 7A, & that area of my garden is extremely well-mulched with fallen leaves.

I dug these glads up for the first winter, but then noticed that a couple of the bulbs I'd missed digging out had survived the winter & bloomed again. So I've never bothered with digging them up since. I have lost some --only 8 (I think) bloomed last summer.

I am zone 6 and mine come up every year even though they are not suppose to.