Near the top of the world, plants grow on soil that rests atop permafrost, or permanently frozen soil. Just like plants in warmer regions, these need nitrogen to grow. The unique aspects of the permafrost environment create new challenges for representing plant-nitrogen interactions. Scientists measured how nitrogen availability to plants varies spatially and temporally in the Arctic tundra. They found that soil moisture plays a big role. In drier areas, nitrogen is present, but in the wrong form for the plants to use. Thawing permafrost increases soil moisture late in the growing season, but the newly available nitrogen near the permafrost boundary isn’t available to roots.