Thujopsis dolabrata

(L.f.) Siebold & Zucc. (1844)

Common names

アスナロ asuhi or あすなろ asunaro [Japanese]; hiba arborvitae; 罗汉柏 luo han bai [Chinese]. "Asunaro" literally means "tomorrow it will become a hinoki", referring to the plant's close resemblance to Chamaecyparis obtusa.

Taxonomic notes

The sole species in Thujopsis Siebold & Zucc. ex Endl. (1842). It was first described in 1817 as Dolophyllum Salisbury, but the publication was not discovered until the early 1990s. Salisbury did not describe an accompanying species and did not make the combination Dolophyllum dolabratum, so the type species remains Thuja dolabrata L.f. Since all publications since 1844 have cited Thujopsis and the genus is widely known by that name in the horticultural trade and to others who have occasion to deal with it, the name Thujopsis has been conserved against Dolophyllum as proposed by Farjon and Hunt (1994). The genus has also been cited, due to orthographic errors, as Thuiopsis and Thuyopsis (Farjon and Hunt 1994).

There are two varieties, the type and T. dolabrata var. hondae Makino.

Thujopsis dolabrata var. dolabrata synonymy:

• Thuja dolabrata Thunb. ex L.f.;
• Platycladus dolabrata (Thunb. ex L.f.) Spach;
• Thujopsis dolabrata var. australis A.Henry.

Molecular phylogenies have generally placed Thujopsis sister to Thuja (Xiang and Li 2005, Yang et al. 2022).

Description

Monoecious trees to 15 m tall; bark thin, gray or reddish brown, peeling off in long strips; crown pyramidal; branches ascending; branchlets 4-6 mm in diameter, arranged in a plane, flattened, lower side with white powder. Leaves decussate, scalelike, dimorphic along branchlets; lateral leaves boat-shaped, deep green adaxially, ovate-lanceolate, 4-7×1.5-2.2 mm, with a white stomatal band abaxially, apex obtuse, slightly incurved, overlapping margins of facial leaves, which are appressed, broadly obovate. Cones terminal, solitary. Pollen cones cylindric; microsporophylls 12-20. Seed cones 1-1.6 cm diameter, subglobose; cones scales 6-8, flat, woody, usually mucronate below apex, each fertile scale with 3-5 seeds. Seeds ellipsoid, 4-5×3-3.5 mm, with 2 thick, lateral, narrow wings. Cotyledons 2 (Fu et al. 1999). See García Esteban et al. (2004) for a detailed characterization of the wood anatomy.

Distribution and Ecology

Japan. The type variety on S Honshu, Kyushu and Shikoku; var. hondai on Hokkaido and N Honshu. Climate cool, moist. Found in mixed conifer and conifer-angiosperm forests from lowland coastal to montane elevations. Typically found in groves, at maturity it is a canopy emergent (Farjon 1998). Hardy to Zone 6 (cold hardiness limit between -23.2°C and -17.8°C) (Bannister and Neuner 2001).

Remarkable Specimens

The only size record I have is for a specimen in Queens Gardens, Nelson, New Zealand, that was 71.9 cm dbh and 14.8 m tall when measured in 2011; it was planted ca. 1895 (Cadwallader 2011). This would easily be the largest of all the ornamental specimens I have seen.

Ethnobotany

I have evidence of one study in dendrochronology (Ohyama et al. 2007).

Observations

No data as of 2026-06-10.

Remarks

Thujopsis combines Thuja with the Greek "opsis" indicating appearance; thus the genus appears similar to Thuja. The epithet is from the Latin dolabra, "hatchet", referring to the leaf shape.

Citations

Cadwallader, B. 2011. New Zealand Tree Register database entry for tree NNR/1127. https://register.notabletrees.org.nz/tree/view/1127, accessed 2017.01.03.

Endlicher, S. L. 1842. Catalogus Horti Academici Vindobonensis. Wien. V. 2, p. 24.

Farjon, Aljos and David R. Hunt. 1994. Proposal to conserve Thujopsis Endl. against Dolophyllum Salisb. (Cupressaceae). Taxon 43(2):291-292.

Xiang, Q., and J. Li. 2005. Derivation of Xanthocyparis and Juniperus from within Cupressus: evidence from sequences of nrDNA internal transcribed spacer region. Harvard Papers in Botany 9:8.

Ohyama, M., M. Ohwada, and M. Suzuki. 2007. Chronology development of Hiba arbor-vitae (Thujopsis dolabrata var. hondae) and dating of timbers from an old building. Journal of Wood Science 53:5367-5373.

Siebold, P. F. von and J. G. Zuccarini. 1844. Flora Japonica sive, Plantae Quas in Imperio Japonico Collegit, Descripsit, ex Parte in Ipsis Locis Pingendas Curavit. V. 2, 89 + 1 pp., 150 tab., Lugduni Batavorum [Leiden] (p. 34).

Yang, Yong, David Kay Ferguson, Bing Liu, Kang-Shan Mao, Lian-Ming Gao, Shou-Zhou Zhang, Tao Wan, Keith Rushforth, and Zhi-Xiang Zhang. 2022. Recent advances on phylogenomics of gymnosperms and a new classification. Plant Diversity 44(4):340-350.

See also

Elwes and Henry 1906-1913 at the Biodiversity Heritage Library (Photo). This series of volumes, privately printed, provides some of the most engaging descriptions of conifers ever published. Although they only treat species cultivated in the U.K. and Ireland, and the taxonomy is a bit dated, still these accounts are thorough, treating such topics as species description, range, varieties, exceptionally old or tall specimens, remarkable trees, and cultivation. Despite being over a century old, they are generally accurate, and are illustrated with some remarkable photographs and lithographs.

Farjon 2005 (as one species with two varieties).