Wintergreen Christmas ferns (Polystichum acrostichoides) with the winter adaptation of a "necrotic hinge": freezing conditions over a period of many days kill off a particular part of the lower stipe support pith, allowing the fern blades to lie flat, without injuring the vasculature. The fern can continue to do photosynthesis while the tree canopy is leafless, when the temperature permits. Laying flat gives some protection to the fronds, though quite a few do not last. They are "wintergreen", not "evergreen", as persistent leaves last for spring-to-spring (1 year). (Feb. 7, 2025, all images and photos are our own. -jcs)