Abstract: This greenhouse watering apparatus has a horizontal support member running centrally for the length of the greenhouse, suspended from above, as from the roof of the greenhouse. A carriage depends from the support member and has trolley wheels rolling along two opposite upper surface portions of the support member in such a way that the suspension of the support member does not interfere with back-and-forth movement of the carriage. A drive wheel moves the carriage along the support member, while a rotary hose reel supported by the carriage reels in or unreels a flexible hose as required. The hose is maximally reeled when the carriage is midway between the ends of the support member and is minimally reeled when the carriage is at either end. During reeling the reel is driven by a slip clutch, which slips during unreeling. A pair of booms, one on each side of the reel, extend out hroizontally, perpendicular to the support member, and each boom is provided with a series of spray nozzles.