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The aim of this paper was to investigate the effect of maturity stage and species on nutritional and rumen fermentation characteristics of two species of greasewood, Black [Sarcobatus vermiculatus (Hook) Torr], and Bailey [Sarcobatus baileyi (Coville) Jepson]. Crude protein (CP) content of both species for all stages ranged from 114.1 to 204.8 g/kg, which is greater than the maintenance requirement of cattle. Highest CP content (204.8 g/kg, P=0.045) was observed for Black greasewood pre-bloom. Highest acid detergent fiber (ADF) and lignin (sa) fractions (311.3 and 103.9 g/kg, P<0.05, respectively) were recorded for Bailey post-bloom, while the lowest ADF and Lignin (sa) fractions (163.4 g/kg and 36.3 g/kg, P<0.05, respectively) were obtained for Black greasewood pre-bloom stage. In vitro dry matter (IVDMD) and organic matter (IVOMD) disappearance, ammonia nitrogen (NH3N), and volatile fatty acid (VFA) content were determined at the end of a 48 h incubation period. Black greasewood was higher (409.0 vs. 366.1 g/kg; P=0.006) in IVOMD than Bailey greasewood. The pre-bloom stage yielded more (P=0.015) IVOMD than the bloom and post bloom stages. No IVOMD difference was observed between bloom and post-bloom stages. Rumen ammonia nitrogen was highest (32.13 mg/100 ml; P=0.005) for Black greasewood pre-bloom. Total VFA was significantly affected by species and maturity. The highest total VFA content was observed for both species pre-bloom. Total VFA remained the same for Black greasewood at bloom and post-bloom stages, while it declined significantly with increased maturity for Bailey. Based on this study Black greasewood has greater potential than Bailey greasewood as a late summer and early fall forage source in salt desert shrub plant communities of the Great Basin. (C) 2015 Published by Elsevier B.V.