Some of the principal controlling factors affecting the Everglades marsh system were combined in a simple model including growth of grass, water levels, rain, transpiration, peat deposition, fire and phosphorus and controlled inflow of water containing nutrients. Using data from published sources, coefficients were estimated and the model was simulated for several regimes, for varying concentrations of nutrient in the inflows and for varying access to fire. The resulting graphs resemble patterns reported from the Everglades, with some regimes producing regular repeating patterns and frequent small fires, whereas other regimes produced erratic and widely fluctuating patterns of vegetation, flood and fire. High phosphorus increased water loss by affecting plant transpiration: oscillations of vegetation and fire caused nutrient oscillations. Inflow of low nutrient water decreased nutrient levels by binding nutrients in plant masses. Continuous high water levels developed large accumulations of vegetation and peat, binding the nutrients, making larger fires when water levels were lowered. If this model is pertinent, a regular period of variation of water inflow and limited nutrients may be means for management of marshes for long range stability.