Studies were conducted in a mountain habitat to determine the effects of altered light and temperature upon the natural growth and/or carbohydrate cycles of Claytonia lanceolata during the period of winter snow cover. Treatments included natural control, light exclusion, and temperature alteration by insulation and by heating for a brief period. Monthly measurements were made of soil temperature (upper 12 cm), shoot development, soluble sugar, and soluble starch. The quantity and quality of light penetrating the snow cover was also determined. About 0.0052% of the available visible light (400-750 nm) penetrated 70 cm of snow and 0.02% penetrated 50 cm of snow. The under snow spectral curve remained constant with a peak at 575 nm, while absolute energy increased 35 times from January to April. Soil temperatures were unchanged by treatments averaging 0.0 to 0.3 C at the surface and slightly warmer at each successive depth. Shoot development and carbohydrate cycles were the same for all treatments. Carbohydrate depletion was generally correlated with increased shoot development. The cycles are traced and discussed. The starch/sugar ratio remained almost constant at one.