I've planted the regular glads in my flower beds close to the foundation of the house in loose soil. Even though I dug them up and stored them inside for the winter. some of the bulbs got left in the ground accidentally. They made it through the winter and grew the next spring, so I leave mine outside now in the same location and they come back every year. I'm in zone 6b.

As long the soil drains well, they are fully ground hardy to zone 6. But there is an issue with the large showy hybrid glads that is similar to tulips - they don't perennialize well, meaning the flowers may be sparse and stalks not well formed. And they can change color over time. That is why most gardeners dig and store just the largest corms or just replant each year.

I've planted a bag of gladiolus between the house and the driveway in Southeastern Mass. A couple survived the winter. For me they are annuals with a few stray survivors next spring.

My folks are not about to go to the trouble of digging up bulbs, nor do I make it up to their place very often. So any plant that can't handle being left outside is a goner.

I have planted both the winter hardy variety as well as the normal, generic BBS store variety up at my folks' place (zone 5/6). Ironically, the winter hardy types did not even survive a single winter while the generic types have been coming up year after year for a decade or two now. Some of the corms are in a raised flowerbed which runs along the front of their house. It can be argued that, on account of this, the bed may serve as a microclimate a zone higher. However, the others are planted by a birdbath smack dab in the middle of their yard (no shelter of any kind) and by a storage shed further back in their yard. They come up just fine.

My mother always grew Gladiolus, Daffodils and Tulips in Kentucky. She never dug her bulbs in the fall, she just put down mulch, such as leaves and grass trimmings from the yard. It helps to insulate the bulbs from the winter cold. Hope this helps you.