Switchgrass (Panicum virgatum L.) and coastal panic grass (Panicum amarum A.S. Hitchc. & Chase) are perennial grasses indigenous to North America. Switchgrass has been shown to have good potential as a biofuel crop in both the US and Canada. IN the Study reported here, seven varieties of switchgrass and one panic grass were evaluated for 5 years under the temperate maritime conditions in Southern England, Both species had 0 or 60 kg N ha(-1) applied annually in spring as treatment. Yield was measured after flowering and when stems were dead in the winter. Yield increased annually for 4-5 years except for the variety Dacotah, and in the fifth year dead stein yields ranged from 8.82 to 13.97 t dm ha(-1). There was no response to N except for one variety in one year. Mineral concentration in biomass was higher at flowering than at dead stem harvest and delaying harvesting further provided more time for P, K and Cl to be leached but yield also declined.