In two adjacent wet grasslands, a Cirsio-Molinietum and a Senecioni-Brometum, in the Netherlands, above-ground phytomass, leaf area index (LAI), and canopy structure were measured at peak flowering season, during three consecutive years. Microclimate profiles in the canopies were measured. The Cirsio-Molinietum produced a smaller phytomass with a larger LAI than the Senecioni-Brometum, and the stem/leaf ratios were different too. Relative distribution of phytomass and leaf area in the canopies were remarkably constant during the three years and independent of total values. Differences in canopy structure including differences in vertical arrangement of phytomass and leaf area, leaf angles and leaf sizes result in differences in light interception patterns, air temperatures and saturation deficits within the canopies, and in soil temperatures. These differences are interpreted in terms of relative growth rates of the constituent species and photosynthetic performances of the vegetation types.