Moss grows in the boundary layer — that region near a surface where friction slows fluid flow dramatically. (This effect explains, for example, why winds are harsher in the middle of a flat parking lot than in the midst of a thick forest; there’s a lot fewer obstacles to break up the flow of the air.) Although moss has some remarkable adaptations that allow it to lose up to 98% of its water, survive decades in a desiccated state, and resume business as usual within half an hour of rehydration, the relatively high humidity in the boundary layer is crucial for protracted periods of productivity. (Here, less wind corresponds to less evaporation.)
It is so important that the depth of the boundary layer directly affects the height the of the moss: this is why mosses on a flat, exposed boulder grow nary a centimeter high, while those deep in the forest may reach several inches tall. The geometry of the moss’ leaves and shoots evolved to increase surface friction further, thus artificially extending the boundary layer! Unfortunately, the relatively stagnant air becomes problematic when the moss must disperse its spores. Thus, it sends up long stalks which reach beyond the calm comfort of the boundary layer such that the spores may catch the breezes aloft.
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Content reference: Gathering Moss by R. W. Kimmerer
I always figured broccoli and cauliflower were related, as well as cabbage and brussel sprouts — but I had no idea they were all the same species, along with kale and collard greens!