Speaking of surprise mushrooms, here's another one!  I tossed the contaminated grain spawn onto the compost pile and ignored it, but it looks like the oyster mushrooms had gotten a good toehold on at least a bit of the grain.  Although there's black mold present, the oyster still managed to produce two little mushrooms.

This doesn't change my analysis of the grain experiment as a failure, but it does testify to the resiliency of oyster mushrooms.  Definitely the easiest mushroom to play with for the backyard homesteader.