Abstract: A method and apparatus for increasing the production of tuber-producing plants per unit area is disclosed. In accordance with this invention, a seed-tuber is planted in soil that is contained in a first box or frame unit. As the plant grows it develops new leaves and axil-buds. When the plant reaches a given height, which is different for different plants, a new layer of soil is added to the first box or frame unit. The new layer of soil does not completely cover the plant. Instead, a layer of soil is added such that the apical meristem is located at the soil surface or about one cm. below the soil surface. As the plant continues to grow another new layer of soil is again added in the manner described. When the level of the soil approaches the top of the first box or frame unit, a second box or frame unit designed to fit on top of the first box or frame unit is placed on top of the first box or frame unit.