The present invention relates to a watering bag (100, 200, 300, 400, 500, 700, 803) for automatic supply of water to plants (801), such as indoor plants. The watering bag comprises a water inlet region (301, 401, 501, 703), a water reservoir (103, 203, 302, 402, 502, 701), and a water outlet region (102, 202, 602, 610), wherein the water inlet region comprises an opening for leading water to the water reservoir, and wherein the water outlet region comprises a friction inducing arrangement (104, 204, 304, 404, 504, 604, 612, 705) for leading water from the water reservoir to the surroundings in a controlled manner.