This raised garden bed is designed with an innovative wicking cell system that closes the bottom of the bed, providing just the right amount of moisture for your plants to thrive. The 3.5" tall wicking cell serves as a reservoir, collecting excess water and redistributing it to your plants over time. It is also designed with air pruning strips so that your plants' roots air prune and don't get oversaturated. Plus, with the wicking cells serving as the bed's bottom, it can be placed on a patio or balcony instead of soil.