Foliage of var. taxifolia in habitat, Ogisawara. iNaturalist observation 135045046 [岸本年郎, 2022.09].
Foliage of var. lutchuensis in habitat, Okinawa. iNaturalist observation 151596294 [takumizuno, 2023.03].
Foliage of var. taxifolia in habitat, Ogisawara. iNaturalist observation 135045046 [岸本年郎, 2022.09].
Foliage of var. lutchuensis in habitat, Okinawa. iNaturalist observation 151596294 [takumizuno, 2023.03].
Juniperus taxifolia
Shima-muro, Hide [Japanese], Luchu juniper.
Two varieties:
This is a member of Juniperus section Juniperus, sister to J. communis var. nipponica (Adams and Schwarzbach 2013, Fig. 8). The two molecular analyses done to date both embed it within various varieties of J. communis itself, but the minimum spanning network of mutation events indicates that J. taxifolia var. lutchuensis is about as distant from J. communis var. nipponica as is J. rigida, and that var. taxifolia is about as distant from J. communis var. nipponica as is J. mairei (Adams and Schwarzbach 2012, 2013), so by this rationale it warrants species rank. Biogeography suggests that this island endemic taxon may be derived from a J. communis-like precursor, and the level of differentiation is consistent with speciation during the latter Pleistocene.
Dioecious erect shrubs or small trees 1-3(-13) m tall. Branches ascending or horizontally spreading; branchlets dull brown, ascending, glabrous. Leaves 7-14 mm long, 1-1.5 mm wide, ternate, awl-shaped, base jointed, light green and slightly ridged on lower surface. Pollen cones ellipsoid, yellowish green, 3-4 mm long, 2 mm wide, with 4 layered ternate scales; scales widely ovate, apex acute. Seed cones on short stalks, densely clothed with small scale leaves, globose, green, ca. 2 mm in diam., consisting of 3 coalescent ovuliferous scales enveloping 3 ovules disposed alternately with the scales. Cones ripening in January to February of the third year, berry-like, globose, 8-9 mm in diameter, purple-brown, 3-seeded. Seeds ovoid, keeled, triangular in cross section, brown, ca. 5 mm long. Flowers February to March, solitary in axils of previous year's shoots (Iwatsuki et al. 1995).
Adams (2014) provides the following key to distinguish the two varieties:
| 1a. | Leaves with one stomatal band or, if two, then midrib faint and not full length of leaf; leaves with acute to obtuse apex, 8-12(-14) mm long; endemic to Ogasawara Islands. | var. taxifolia |
| 1b. | Leaves with two distinct stomatal bands and a midrib running the full length of leaf; leaves with acute to apiculate apex, 7-10 mm long; endemic to Ryukyu Islands and the S coast of Oshima Island. | var. lutchuensis |
Japan: Ogasawara, Oshima, and Ryukyu Islands. Grows from near sea level to 300 m elevation (the highest points in the islands), in sunny stony places (Iwatsuki et al. 1995). Occurs as a low shrub in the marine riparian zone, and as a shrub or small, erect tree further inland in tall grassland and thickets; primarily on rocks, or rocky or gravely soils. It is subjected to strong and moist, salt-laden ocean winds, and may be inferred to have fairly high salt tolerance (as do many junipers) (Farjon 2010).
Zone 9 (cold hardiness limit between -6.6°C and -1.1°C) (Bannister and Neuner 2001).
In 2010, the IUCN assessed the species as "Near Threatened" because "no actual threats are currently known to occur, however, the extremely fragmented distribution by nature of its occurrence on oceanic islands and its consequently small area of occupancy make this species susceptible to events that could reduce subpopulations" (Katsuki et al. 2013). They also noted that it might qualify as "Vulnerable", and this is also a more appropriate rank if the varieties are considered separately, as each is even more vulnerable to stochastic events.
No data as of 2025.01.13.
On some islands (e.g. Okinawa) J. taxifolia is used as a windbreak, and as a garden ornamental. It is a rare ornamental in mainland Japan, and in the islands, the wood formerly saw occasional use in construction and as fuel (Farjon 2010).
Var. lutchuenensis can be seen in Keramashoto National Park, Okinawa, and var. taxifolia in Ogasawara National Park, Ogasawara.
The first reference to this plant is by Thunberg (1784), who called it J. barbadensis or "Nankin sugi" (Nanking sugi, in which case a syn. of J. chinensis) and cited its occurrence in the prefecture of Nagasaki. It was next noticed by Hooker and Arnott (1838), who in June of 1827 found it in the Bonin Islands (today the Ogasawara Islands), an archipelago S of Honshu. They gave it the epithet taxifolia, meaning that the foliage resembles that of the yew, Taxus. Modern observers may not see much of a resemblance.
Adams, Robert P. 2014. Junipers of the World: The Genus Juniperus. Fourth edition. Trafford Publishing. Brief versions of the descriptions are available online at Adam's website, www.juniperus.org.
Adams, Robert P. and Andrea E. Schwarzbach. 2012. Taxonomy of Juniperus section Juniperus: sequence analysis of nrDNA and five cpDNA regions. Phytologia 94:269-276.
Adams, R. P., and A. E. Schwarzbach. 2013. Phylogeny of Juniperus using nrDNA and four cpDNRA regions. Phytologia 95:179-187.
Hooker, W. J. and G. A. W. Arnott. 1838. The botany of Captain Beechey's voyage, p. 271. Available: Biodiversity Heritage Library, accessed 2025.01.13.
Katsuki, T., A. Farjon, and D. Luscombe. 2013. Juniperus taxifolia. The IUCN Red List of Threatened Species 2013: e.T32042A2809466. https://dx.doi.org/10.2305/IUCN.UK.2013-1.RLTS.T32042A2809466.en, accessed 2025.01.13.
Koidzumi, Geniti. 1918. Contributiones ad Floram Asiae Orientalis. Shokubutsugaku zasshi (Botanical Magazine Tokyo) 32:138. Biodiversity Heritage Library, accessed 2025.01.13.
Satake, Y. 1962. Bulletin of the National Science Museum, Tokyo 6(2):193.
Thunberg, C. P. 1784. Flora japonica sistens plantas insularum japonicarum, p. 264. Available: Biodiversity Heritage Library, accessed 2025.01.13.
Farjon (2005) provides a detailed account, with illustrations.
Last Modified 2025-01-13
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