Dave, I know this may be a really unnecessary concern of mine but I'm going to throw it out there.
I suppose it's going to take a lot of soil to fill from the center cylinder out to the lower level. Wondering should the day come where you'd need to remove and replace the soil due to compaction or just new nutrients. Dave, how will you dig down in the middle cylinder? I'm kind of thinking if I were to plant that portion I'd put a filler space at the bottom of the center portion. I don't think herbs need lots of depth. I'm thinking of plastic storage containers with lid on. Just empty storage bins with lids. Has this notion of possibly needing to replace the soil concerned you?
