Blue-green algae, including species of Oscillatoria, Lyngbya, Microcystis, and Nostocaceae were isolated from green sand associated with Hudsonia tomentosa. Green sands were consistently found in the buried phyllosphere and rhizosphere of Hudsonia and on the surface to varying depths under Hudsonia plants. Organisms in these sands fixed nitrogen at maximum rates of 1 nmol C2H4∙g soil−1∙h−1. Seasonal variation in rates was largely explained by optima of 30% soil water content and 28 to 33 °C soil temperature. Green sands were not associated with any other vascular plant at the study sites. The results suggest a preference of free-living blue-green algae for Hudsonia which may relate to the ability of this dwarf shrub to colonize nutrient-poor sand sites, such as blowouts and sand dunes in the Pinus banksiana – lichen woodlands of northeastern Alberta