I think I'd stick to planting plants in it that don't get too large. Might have to supplement with fertilizer, and for sure until the worms get into major production.
Dave, did you put any fert on the plants you planted?
I'm visualizing some other uses for this, like a tower of Caladiums in a shady spot in my garden . . . keep the worms cooler, not quite so much water demand, plants don't get too huge . . lots of possibilities!
