I've inadvertently killed potted ivy several times myself! But English ivy fills one corner of my backyard, having spread from the neighbors', and has to be cut back twice a year because it would fill the yard in a few years if we let it. Big, fat vines - even right under the evergreens, where nothing much can get going. I found out only last year that it threatens wild forest plants significantly, and is an officially designated Class C Noxious Weed in
Washington state.
(It doesn't hold a candle to the invasive Himalayan blackberry, though, IMO, which is absolutely everywhere. Forms huge hideous thickets as tall as a house, and it has deep roots that allow it to come right back with full-sized vines if it's torn out. Hate! You can't kill it with fire, even goats don't destroy it - and the berries are rarely any good. At least ivy has the ability to be kind of pretty sometimes.)
- mirfak