I moved to a property on the East coast with a somewhat wild backyard and a lot of big oaks and maples. I kept away from anything I thought resembled poison ivy. One particular oak had a hairy vine wrapped around it that was 5-6" in diameter extending 60+ ft up into the canopy; it didn't have any leaves I could see. I removed it to keep it from choking the oak tree. I learned the hard way that poison ivy vines can get _really_ big and are hairy.