The development of flowering shoots was studied by daily observation of plants grown in aquaria under controlled conditions. Inflorescences (‘spathes’) of a rhipidium develop and flower one after another, thus elongating the fertile shoot. Rhipidia of the same fertile shoot flower more or less synchronously. The whole course of flowering of one generative shoot is given. There is no peak in flowering in the field, as a consequence of the long time-period over which a fertile shoot flowers. In the tidal zone near Bergen op Zoom (The Netherlands) the production of new shoots increases up until the end of August and then gradually declines. At the beginning of October, the development of new fertile shoots ceases, and at the end of this month nearly all plants have withered or are washed away. In the stagnant water of the Grevelingen (The Netherlands) the production of fertile shoots increases in July, is constant or slightly fluctuating in August and suddenly stops at the beginning of September. The flowering rate is somewhat higher in the Grevelingen than near Bergen op Zoom.