Values for aboveground biomass (standing crop) from December 1982 to December 1985 at two sites in Lake Alexandrina (South Island, New Zealand) are reported. Weak seasonality was apparent forChara fibrosaat 1.8 m,Elodea can‐adensis, Isoetes alpinus, andChara globularis. The biomass of other species did not appear to be directly related to annual changes in solar radiation and water temperature. Annual growth for six species was estimated from annual changes in above‐ground biomass and ranged from 296 mg C m‐2day‐1(forE. canadensis)to 17 mg Cm‐2day‐1(forChara corallina). The growth of two species was also determined using short‐term measurements of stem and branch length and gave estimates of 177 and 545 mg C m‐2day‐1forE. canadensisat two sites and 97 mg Cm‐2day‐1forMyriophyllum triphyllum.