I'm on Long Island and when I lived in CT i never would have considered leaving Glads in the ground during the winter..but wouldn't you know that when I first put ones in in this house the winter sortof snuck up on me and next thing I knew there was freezing rain, frozen ground, snow, more freezing rain..and on and on and on...no way I could have gotten to them. I was sure they were goners, BUT they made it through the winter just fine and were among the first things popping up the next year. I then learned from a neighbor that she's never pulled hers in the 15+ years she lived here so I've started leaving a bunch in the ground all winter now and then come mid-april, late april, and then mid-may I put additional ones in and get flowers for weeks.

Not sure where in NY you are but if you are similar to my location I suggest trying to leave some in the ground this coming winter (nothing in a super shaded area though..although those also came up this year so..who knows. haha). I don't mulch either, or put leaves over them or anything; I just pull the stalks once they are brown and call it gladiola gardening = )