Betula chichibuensis

Betula chichibuensis is a multi-stemmed shrub or small deciduous tree that reaches 8–10 meters (26–33 ft) tall in the wild and about 5 meters (16 feet) tall in captivity. The Chichibu birch is very long-lived due to its sprouting habit, but its self-incompatibility means two individuals must be close enough together to cross-pollinate, making seed production unreliable in smaller populations. The bark of the Chichibu birch is light brown and flaky with horizontal lenticels. Twigs from it are nearly hairless and can reach up to 3 mm in diameter. The leaves are alternately placed on the stem, and their shape is ovate, acute, rounded or slightly cordate at the base. They are 30–75 mm long by 15–45 mm wide, glabrous and green on their upper surface, and have white hairs on the underside. They have up to 18 pairs of deep veins and are serrated, with 1–3 teeth between each tooth ending a secondary vein. Chichibu birch is monoecious: an individual has both male and female catkins. Female catkins are red-violet and erect, while male catkins expand in the spring with tiny nutlet fruits that are chestnut brown in color and about 0.15 mm wide.

Chichibu birches are extremely rare in the wild, growing only on a handful of limestone outcrops in the mountains of the Japanese island of Honshu. From their first description as a distinct species by Hiroshi Hara in 1965 up until roughly 2015, B. chichibuensis had been found exclusively in a single stand in the Okuchichibu Mountains (Chichibu Tama Kai National Park), where only 21 Chichibu birches were counted in 1993. As of 2017, at least eight additional small stands of B. chichibuensis were found by Dr. Toshihide Hirao, mostly in the Kitakami Mountains of northeast Honshu. A 2014 expedition to the Okuchichibu Mountains location found B. chichibuensis growing on an exposed limestone mountain face near the Karisaka Tunnel, alongside plants including Sasa bamboo, Chamaecyparis obtusa cypresses, Juniperus rigida junipers, and Acer pictum maples.