Abstract: Carts for supporting indoor growth of plants, modular plant growing systems including the carts, and methods of growing plants indoors are disclosed herein. The carts include a support frame, a plurality of light sources, an electrical input structure, an irrigation water distribution manifold, and an irrigation water collection manifold. The modular plant growing systems include a racking system and the carts. The methods include positioning a plurality of plants, positioning at least one flood tray, positioning a cart, fluidly interconnecting a water source, electrically interconnecting an electrical outlet to an electrical input structure, and promoting growth.