Alnus japonica
Common name: 
Japanese Alder
AL-nus ja-PON-i-ka
Native to (or naturalized in) Oregon: 
  • Broadleaf deciduous tree, to about 80 ft (25 m) tall, pyramidal, dense foliage.  Bark gray-brown, smooth.  Leaves alternate, simple, narrow-elliptic to oblong-lanceolate, 6-12 cm long, 7-11 lateral veins on each side of midrib, tip acuminate, base wedge-shaped, margin remotely serrate, blade glabrous (without hairs) or pubescent when young, dark green, light green below; petiole 1.5-2.5 cm long.  Male (pollen) catkins in small clusters at stem tips, about 5-8 cm long at pollination.  Female flower catkins 2-3 cm long, erect; mature seed cones large, egg-shaped, 2.5-3 cm long.
  • Sun to partial shade, apparently not fussy about soil type, grows in wet and infertile soils.  
  • Hardy to USDA Zone 5         Native to far eastern Russia, China (Anhui, Hebei, Henan, Jiangsu, Jilin, Liaoning, Shandong), Korea and Japan.
  • Oregon State Univ., Peavy Arboretum
Click image to enlarge
  • plant habit, spring

    plant habit, spring

  • male catkins

    male catkins

  • catkins


  • plant habit, summer

    plant habit, summer

  • leafy branch

    leafy branch

  • leaves


  • leaf


  • cones and male catkins, Sept.

    cones and male catkins, Sept.

  • leaves and male catkins, Oct.

    leaves and male catkins, Oct.

  • spent cones

    spent cones

  • trunk, bark

    trunk, bark

  • winter twig, buds

    winter twig, buds