A sub-irrigated planter with a water reservoir beneath the soil, where water wicks up to the root zone and the soil surface stays drier than the reservoir.
Jeremy points out that the soil in the earth box never really gets dry because the reservoir is open to the air and the plants are drinking from below, so it acts differently than the other containers and can confuse you if you are comparing plant drink rates.
Discussed in: Ep 010 · Ep 014 · Ep 018 · Ep 022 · Ep 025 · Ep 026 · Ep 028 · Ep 035 · Ep 041 · Ep 042