obtusa – rounded, in reference to leaves (branchlets) being blunt/rounded at the tips

Native range: Japan & Taiwan

Leaves:

• branchlets are arranged in one horizontal plane
• scales closely appressed, of 2 sizes
• lateral pair much larger 1/12” long
• blunt at apex
• white “Y” markings below (stomata)

Cones:

• monoecious
• males – yellow/orange brown
• females – solitary, greenish-brown
• short stalked, globose cones 1/3–3/8” across
• 8 (10) scales

Other characteristics:

• ultimately 50–75’(to 40 m.) tall to 10’ (3 m.) diameter, 10–20’ (3–6 m.) spread
• bark reddish brown, shedding in strips
• pyramidal shape
• spreading branches with flattened horizontal branchlets that droop at the ends
• branchlets are rounded at the end (obtuse) instead of coming to a point as in Thuja or Chamaecyparis lawsoniana.

Relevant info:

• usually smaller cultivar forms are used in managed landscapes in PNW
• in Japan, hinoki = fire tree
  • used to make fire by friction, a practice still employed at Shinto shrines
• one of the ‘Five sacred Trees of Kiso’ in Japan
• historically, very important species used in Japanese architecture
• considered “near threatened” by IUCN due to habitat fragmentation and overexploitation

Ecology & Adaptations:

• native to Southern Japan & Taiwan
• found in temperate mixed Chamaecyparis and broad-leaved mountain forests below 2,800 m., also exposed sites at high elevation
• pollination by wind
• seed dispersal – small “wings” facilitate dispersal by wind
• sexual reproduction & competition:
  • wood of downed mature C. obtusa trees are key sites of C. obtusa seedling regeneration
  • wood contains salicylic acid, one of several compounds that appear to have an inhibiting (allelopathic) effect on the growth of other tree, shrub and herbaceous species
• vegetative reproduction – may be limited to layering that occurs when trees are felled by wind
• herbivory defense – compounds (terpenes) produced in the tissues inhibit some mammal herbivory (e.g., cervids such as deer) and insect infestation