Hierochloë odorata (L.) Beauv. is restricted to the upper zone of salt marshes and rarely becomes dominant.
In the field, the species was found not to have strict N, P, K requirements. It grew in a range of pH values from 4.3 to 7.9, tolerated salinities up to 500 mhos and favoured soils with a moisture content from 25 to 30%. It grew in situations with a mean water table between 14 and 28 cm below the surface. Natural shading in the field was found to increase the heights of plants by about 30%. The application of fertilizer in the field increased the height of sweet grass but also stimulated the growth of associated species. In the greenhouse, the effects of different soils and fertilizers on plant growth were assessed. Inorganic fertilizer (12:18:12) application produced more leaves and tillers than organic fertilizer (6:2:0).
Sweet grass grows in a zone of reduced competition between the dune species and the salt-marsh species. Near the salt-marsh, the species may be limited by high salt concentration. The low levels of competition offered by cultivation and the responsiveness of the species to fertilizer suggests that cultivation of Hierochloë odorata may be successful.