Abstract: A plant holder for a hydroponic system includes a first structure shaped to hold a plant during an early growth stage and a second structure configured to hold the first structure during a later growth stage. The first structure is sized to directly fit in a tray having a high plant density. The second structure is sized to directly fit openings in a tray having a lower plant density. Plants in early stages of growth may be efficiently grown with the first structures in the high-plant-density tray, and the first structures with the plants may be easily transferred to more spacious trays without damaging the plants.