Litter of Tortula ruralis, Artemisia tridentata, and Chrysothamnus viscidiflorus retarded germination and early growth of Stipa thurberiana, Sitanion hystrix, and Agropyron spicatum grow in a soil medium under greenhouse conditions. Four weeks after germination, growth was stimulated by the presence of these litter materials. Stimulation was attributed to a greater availability of nitrogen in the Tortula and Artemisia litter, but in the case of Chrysothamnus there is some evidence for the occurrence of an additional growth—promoting substance.