Little has been done to evaluate the midwinter crude protein, phosphorus, and in vitro digestibility of subspecies and accessions of rubber rabbitbrush (Clirysothumnus nauseosus ssp.) For those few studies that have been conducted, subspecies and accessional variation was not addressed. This study tested the hypothesis that certain subspecies and accessions of rubber rabbitbrush grown in a common garden on homogeneous soil would exceed other subspecies and accessions in crude protein, phosphorus, and in vitro digestibility. Also, the level of these traits for the various subspecies and accessions of rubber rabbitbrush were compared to other species of winter forages. rumens of wintering deer in California study contained rubber rabbitbrush. Significant differences for all 3 traits occurred among subspecies and accessions. Some accessions of rubber rabbitbrush were ranked high in crude protein, phosphorus, and digestibility in comparison to other species of winter forages. Enough variation exists among subspecies and accessions that a selection program could result in the development of superior forms of rubber rabbitbrush to be used as a winter forage. In general, energy, protein, and phosphorus are in short supply in winter forages (Dietz 1965). Therefore, we designed this study to test the hypothesis that certain subspecies and accessions of rubber rabbitbrush, grown in a common garden on homogeneous soil, would exceed other subspecies and accessions in crude protein, phosphorus and in vitro digestibility. We compared in a general way the levels of crude protein, phosphorus, and in vitro digestibility of the various subspecies and &cessions of rubber rabbitbrush to other species of winter forages. Materials and Methods Seeds from 7 subspecies of rubber rabbitbrush were collected from 19 native populations from the western United States. Table 1 lists subspecies, accessions, and locations where seeds were acquired. Seeds were cleaned and transplants produced and placed