This study was conducted on three naturally growing populations of the perennial grasses Panicum turgidum Forssk, Lasiurus scindicus Henrard and Pennisetum divisum Henrard in Egypt, south west Saudi Arabia and Qatar. Vegetative reproduction occurs by rhizome growth and sexual reproduction by tillering, where each tiller may end with a spike. The failure of sexual reproduction is mainly related to the extremely arid conditions and the overgrazing of flowering branches or seeds before dispersal. Phenological behaviour varied among species and differed within the same species in the three study areas. The earliness/lateness and narrow/wide spectrum of the active phenological phases (vegetative growth, flowering and fruiting) were species-dependent rather than locality-dependent. The phenophases of the three species in Saudi Arabia and Qatar proceeded at a faster rate than in Egypt. The plants collected from Saudi Arabia and Egypt attained higher energy content than those collected from Qatar. The overall energy content of P. turgidum (over 6 kcal. g -1 dry weight) is higher than that of L. scindicus and P. divisum (less than 6 kcal. g -1 dry weight). During the peak flowering/fruiting time, the fruits and rhizomes of the three species showed higher energy content than the roots and shoots. When the growth characteristics and energy content were taken as a measure of the grazing value, P. turgidum had better value as a forage plant than the other two species.