A horticultural cell system which comprises a belt of sheet material folded in half longitudinally along a fold line and having its two layers sealed along lines transverse to and spaced apart along the belt. The lines of seals extend from the free edges of the layers only partially across the width of the belt toward the fold line. The seals form and separate a series of cells, each suitable for receiving the root system of a mature plant, and an alternating series of web portions which space the cells a desired distance apart. The portions of the layers adjacent to the fold line form a continuous tube which is common to and communicates with each of the cells, and has a greater width than that of the cells. The root system of each of the plants can extend into the tube, which provides a common plant support system and allows the root systems to expand to a greater degree than if confined solely to the individual cells.