A growth model has been developed for warm‐season perennial grasses which relates seasonal distribution of dry matter to calendar time through the probability equation, and which relates total seasonal dry matter to harvest interval through a linear‐exponential equation. The model is used to describe response of ‘Tifton‐9’ bahiagrass(Paspalum notatumFlögge) to time and harvest interval at Quincy, FL. It is also shown that yield response to applied nitrogen (N) is described by the logistic equation, in agreement with earlier results for bahiagrass and other forage grasses. This model removes the restriction of harvest interval to 6 or 7 wk of the previous linear growth model. Maximum dry matter yield exceeded 20 Mg ha‐1. Maximum incremental dry matter response to applied N occurred at approximately 140 kg N ha‐1. A harvest interval of 8 wk provided peak dry matter production. The mean and standard deviation of dry matter distribution were 28.5 wk and 6.0 wk, respectively. Correlation coefficients of the models with data exceeded 0.99. Effects of harvest interval and applied N are easily accounted for with this model, which uses analytical functions and avoids the need for finite difference techniques.