I was told when the nights are consistently in the 50-60 degree range. I've already put mine out, and we've had several nights in the low 50's, even high 40's and they have survived. Of course, when I first put them out, I put them in a pretty sheltered location just to get them used to being outside again. In another week or so, I'll move them out into more light and exposure.

If your soil temp is in the 50s, I'd say go ahead and plant it. It's not going to grow until the soil warms up considerably anyway, but it won't hurt it. Probably a colocasia esculenta.

Susan