The effects of light (e.g. light intensity and light period) and temperature on the anthesis processes ofHolcus lanatusL.,Festuca rubraL. andPoa annuaL. were investigated under experimental conditions in climate rooms. All three grasses have a daily periodicity in their anthesis with one maximum and one minimum a day. This daily periodicity was not affected by either light or temperature factors. Each of the grass species studied have anthesis patterns based on specific characters which are not influenced by light intensity or light period. These light factors affected the three grass species only in their anther production.