Amazing sweet potato vine

I grew sweet potato slips this spring in my greenhouse. I planted a few, not as many as I wanted, but oh well. I stopped using my greenhouse for anything in the summer because it's way too hot. I watered the sweet potato for a while, but when I decided it was to late to plant more slips I didn't bother. You would think they would die. Not only did they not die, they grew like crazy. It totally amazes me. The temperature in there even though the door has been open getting super hot and I haven't watered for 4, maybe even 6 weeks. I don't think the vines I planted and care for look this good.