The Fir Tree Moss (Dendroalsia abietinum) can be found clinging to the trunks of Oregon White Oaks throughout the arboretum. At the moment, they are lush and green from the rain. Mosses lack roots, so they depend on the rain to shower them with water so they can photosynthesize, reproduce, and grow. The Pacific Northwest (PNW) wet weather is the perfect climate for mosses. In Plants of the Pacific Northwest Coast, Pojar and MacKinnon say there are about 700 species of mosses in this area. That said, the summers here in the Willamette Valley are hot and dry. The whole summer might only see a couple of small rainfalls. So what does that mean for all the mosses growing here that need to be bathed in water to carry out photosynthesis and grow? They have a miraculous ability to adjust their physiological processes according to environmental moisture levels. This is called poikilohydry. They are happily photosynthesizing if the environment is wet during the fall, winter, and spring. When the rain temporarily halts for the summer, the mosses contentedly dry up and go dormant, patiently waiting for the rain to return.
Each source that I read mentioned the characteristic of this species to bend downward and curl inward when it is dry. Pojar and MacKinnon label it with the common name Plume Moss which I like.
