Thanks! I really should have just held my horses and bought more media, but alas. I'm pretty afraid to upset this thing now but if I see an opportunity in the spring as you mentioned I'll probably go for it.

Water hasn't really been a problem. I've got some drainage holes drilled about 2/3 of the way up the side of this thing which prevents flooding. It's been a brutal summer here at times, and even so I've only had to add water twice (I just stick a finger into the moss top dressing to check it once or twice a week; it's usually quite damp).

As for warmth, there's a boiler room in my basement which vents to the outside along the wall of my apartment. I'm hoping that that will create a warm enough spot to put this planter that I won't have to worry about extended deep freezes. Maybe that and a frost blanket or just a pile of leaves on top of this thing will keep the plants happy until next season, when the depth of this planter may or may not become a problem for the plants as they send their roots deeper....

This may well be a cycle of problems I've just created for myself, but we'll see!!