The present invention relates to a single-piece tray for hydroponic cultivation, composed of a plastic material shaped so as to define inside the tray a plurality of identical cultivation cells. Each cultivation cell has: a housing defining a raised plane and configured to house a bulb or seedling to be cultivated, with a hole having dimensions such as to support the bulb or seedling to be cultivated without letting it fall through, while allowing its roots to protrude below the tray; a buoyant portion, defining a lowered plane intended to sink below a waterline, and delimited by side walls, each buoyant portion defining: - a bottomside with a first height, intended to remain below the waterline, - a waterline zone with a second height, which remains above the waterline when the bulb or seedling to be cultivated is placed in the cultivation cell and is intended to sink completely below the waterline when the bulb or seedling to be cultivated has become a mature plant, - a topside with a third height, which re
