How much space do I need for a Tower Garden? How big is Tower Garden? by Montecito Urban Farms | Jul 23, 2017 | 0 comments Tower Garden needs a minimum space of 2.5 feet by 2.5 feet. The basic Tower Garden unit is 5 feet tall and can grow 20 plants. You may choose to purchase an Extension Kit, which increases its maximum height to 6 feet and its capacity to 28 plants. Submit a Comment Cancel replyYou must be logged in to post a comment.