pjefferson, I don't know where you live, but in the US, they are the plastic containers that milk is sold in at every grocery store. They have a handle too, which makes them easy to carry.
We're getting ready to move out of state, so I decided not to put my greenhouse up this winter. I would have loved to have kept some plants in there, but it would have been too tempting to start some seeds too. I'm not good with that kind of temptation!
So, I'll have to wait until next winter to try out the milk jugs for myself!
