When the bank falls away, big sage shows her roots.
Look at that: no great fussiness, just a few roots sinking down deep in a narrow column. These roots are easily twice as deep as the plant is high. No effort is wasted in gathering water from a broad area here. The trick here is to go down deep, which one can do when one doesn’t lose a lot of water to evaporation: one doesn’t need a lot. Note how water closer to the surface is not accessed by these deep roots. Perhaps when water down even deeper migrates upward to replace the wetness in the soil near the surface, the sage catches it on the way by. Perhaps the drought we see on the cliff face here is really an effect of the sage mining the water in behind, at exactly that level. These are intriguing but unproven hypotheses. One thing seems obvious, though: sagebrush is not worrying about water in the top profile of the soil. Her interest is in the airier soils below. The rest are for her companions. By mining the deep water slowly, so slowly that it follow her up, big sage is effectively acting as the stem of the grasses and flowers around her. Because of her, they need fewer roots.