The interior botanical treatment cells that process household greywater are, as noted in the previous chapter, also food production zones. The nutrient-rich greywater that flows through the cells supports vigorous plant growth without any additional fertilizer. Species well-suited to interior botanical cells include banana, papaya, fig, various herbs (mint, lemon balm, comfrey), ornamental edibles, and many tropical vegetables that would not survive outdoor winters in temperate climates.

Designing the interior botanical cell as an intentional food production system — selecting productive species rather than merely decorative ones, designing for harvesting access, and managing the cell’s plant community for food production as well as waste treatment performance — requires some additional thought during the design phase but adds significant productive capacity at no additional material cost.