Surprise shamrocks!

My roommate brought home two pots of shamrocks on St. Patrick’s Day. Actually I guess some kind of oxalis, or false shamrock. The last thing I need is MORE plants in the house, so when it got warm I put them outside. One dried up and then disappeared before I got around to planting them. Now I think a squirrel must have buried it, because suddenly it’s coming up all over! And blooming – I’ve never seen them bloom before. Supposedly they can live in zone 4 but I’ve only ever seen them used as houseplants. Apparently they can be invasive outdoors, which I didn’t know when I planted the one, but often species that are invasive in other zones have trouble just hanging on here. (Kudzu doesn’t even stand a chance.) We shall see. Link to huge picture. That’s the one that disappeared.