On Jul 25, 6:25 pm, K wrote:
I'd recommend going for something extremely drought tolerant, eg
succulents, in which case you could get away with 6 inches high. Or you
could (and this might be more effective) use it as a box in which you
stand potted plants according to the season, eg pots of bulbs in spring
giving way to drought loving bedding plants in summer.
Either way, you'll need it either heavy or fixed to the wall else you'll
end up with a nasty mixed heap of toddler, plants, and broken box.

At first I thought that too, the succulents bit, because I've lots of
them in tiny pots everywhere, but then I ended up with the 'mixed
heap'! Can't wait for jgkg to tell us how high is this wall of his.