Agronomic data on most broad-leaved species of grasslands are scarce. The aim of this study was to obtain novel information on herbage DM yield and forage quality for several forb species, and on species differences and seasonal patterns across harvests and in successive years. Four non-leguminous forbs [salad burnet (Sanguisorba minor), caraway (Carum carvi), chicory (Cichorium intybus) and ribwort plantain (Plantago lanceolata)] and three leguminous forbs [yellow sweet clover (Melilotus officinalis), lucerne (Medicago sativa) and birdsfoot trefoil (Lotus corniculatus)] and a perennial ryegrass–white clover mixture were investigated in a small-plot cutting trial in Denmark during 2009 and 2010. Plots were harvested four times per year. On average, annual herbage yield was highest for lucerne (15·4 t DM) and grass–white clover (12·5 t DM ha−1), and lowest for salad burnet (4·6 t DM ha−1) and yellow sweet clover (3·9 t DM ha−1). Ribwort plantain and lucerne had the highest concentrations of acid detergent fibre (339 and 321 g kg−1 DM respectively) and lignin (78 and 67 g kg−1 DM respectively); contents in other species were similar to grass–white clover (275 and 49 g kg−1 DM respectively). No common feature was found within the functional groups of non-leguminous forbs and leguminous forbs, other than higher crude protein contents (198–206 g kg−1 DM) in the legumes. DM yield and fibre content were lowest in October. Digestibility declined with higher temperature and increasing fibre content. Results are discussed in terms of the potential of forbs to contribute to forage resources in farming practice.