A watering/drainage arrangement for a multi-layer horticultural structure wherein during watering, water from a series of water release outlets is sprayed through an aperture of a flood tray which fills to a selected level and maintained at this level by the continued supply of sprayed water through the water release outlets and the drainage of overflow via a weir edge of the flood tray and during drainage, supply of water to the release outlets is terminated thereby preventing water being sprayed into the aperture of the flood tray thereby allowing the discharge of water through the aperture of the flood tray.
