Juniperus coxii (垂枝柏, coffin juniper) description

Juniperus coxii

A. B. Jacks. 1932

Common names

垂枝柏 chui zhi bai [Chinese], coffin juniper.

Taxonomic notes

Syn.: Juniperus recurva Buch.-Ham. var. coxii (A.B. Jacks.) Melville 1959; Sabina recurva (Buch.-Ham.) Antoine var. coxii (A.B. Jacks.) W.C. Cheng & L.K. Fu 1978 (Adams 2004). Type: Cultivated tree in Exbury Gardens, Hampshire, England, grown from seed collected 1920 by R. Farrer and E.H.M. Cox in Chimli Valley, Myanmar, R. Farrer 1407.

J. coxii is often treated as a variety of J. recurva. Both junipers belong to the turbinate seed cone clade, which includes about 15 central Asian species of, generally, very similar appearance, as discussed in Juniperus. Taxonomic relationships within the clade are founded mainly on molecular evidence, and indicate that J. coxii is sister to J. uncinata in a clade that also includes J. indica, J. fargesii, and J. rushforthiana (Adams and Schwarzbach 2012, 2013). There is some reason to question the molecular analyses, which are based on analysis of a single specimen growing in the U.K. (Adams 2000, Adams et al. 2012), but no other analyses are available at this writing. Adams (2000), describing his rationale for treating this taxon as a full species, makes the following points.

Jackson (1932) noted the resemblance to J. recurva, with J. coxii being more pendulous, having longer tapering leaves which have two greenish-white bands on the ventral surface (in contrast to a single white stomatal band for J. recurva) and having a strong central axis (vs. occasionally multiple stems in J. recurva).
It seems to grow in more mesic sites than J. recurva.
The leaf essential oil contains a number of compounds not found in J. recurva, and is overall very distinct.
This taxon is reproducing itself under natural conditions.

Description

Dioecious evergreen shrubs, or trees to 40 m tall and 200 cm dbh, with a crown of long, pendulous branches. Bark brown to cinnamon, exfoliating in wide strips or plates. Twigs long, pendulous. Leaves include both decurrent and scale types, 6-10 × 0.8-1.0 mm, straight or slightly incurved, diverging at 30-45° from the shoot, the inner (adaxial) surface of the leaves bearing 2 greenish-white stomatal bands and a prominent green midvein. Seed cones turbinate, green-brown, nearly black on maturity, maturing in 2 years, 6-8 × 5-6 mm. Seeds 1 per cone, conical-ovoid, 5-6 × 3-4 mm bearing 3 ridges (Adams 2004, Farjon 2010).

Distribution and Ecology

Nepal, Bhutan, N Myanmar, India: Sikkim and perhaps Arunachal Pradesh, China: Yunnan and Xizang (Tibet). Found in temperate montane evergreen rainforest at elevations of 2,400 to 3,000 m; often planted, especially in Yunnan (Adams 2004, Farjon 2010, Farjon and Filer 2013). Associates include the conifers Abies forrestii, A. densa, A. delavayi, Larix griffithii, L. potaninii, Picea spinulosa, P. likiangensis, and Pinus wallichiana, as well as species of Lauraceae and Fagaceae, often with a Rhododendron understory; the juniper is usually on sites with reduced canopy closure due to rocky substrates or disturbances such as logging or grazing (Farjon 2010). Hardy to Zone 7 (cold hardiness limit between -17.7°C and -12.2°C) (Bannister and Neuner 2001).

The IUCN lists this taxon as "near threatened" due to a declining population trend, but there are significant uncertainties. Its area of occupancy appears to be declining in Yunnan, but to be stable elsewhere in its range. Its precise range and area of occupancy are not well-known. There are no existing conservation efforts, although it does grow in some protected areas (Li et al. 2013).

Remarkable Specimens

No specimen data available, but the reported size maxima of 200 cm dbh or 40 m tall would rank high among the species of Juniperus.

Ethnobotany

Used for coffins and furniture (Adams 2004). In Europe and North America, it is a reasonably popular ornamental in areas with the appropriate wet-temperate climate (Li et al. 2013); it seems to be particularly popular in the U.K. and New Zealand.

Observations

Remarks

The epithet honors the collector, E. H. M. Cox.

Citations

Adams, R.P. 2000. Systematics of the one seeded Juniperus of the eastern hemisphere based on leaf essential oils and random amplified polymorphic DNAs (RAPDs). Biochemical Systematics and Ecology 28: 529-543.

Adams, R. P. 2004. Junipers of the World, 2nd ed. Vancouver, BC: Trafford Publ. Co. 402pp.

Adams, R. P., and A. E. Schwarzbach. 2012. Taxonomy of the turbinate shaped seed cone taxa of Juniperus, section Sabina: sequence analysis of nrDNA and four cpDNA regions. Phytologia 94(3):388-403.

Adams, R. P., and A. E. Schwarzbach. 2013. Taxonomy of the turbinate shaped seed cone taxa of Juniperus, section Sabina: Revisited. Phytologia 95:122–124.

Farjon, Aljos. 2010. A Handbook of the World's Conifers. Leiden, Netherlands: Brill Academic Publishers.

Farjon, Aljos and Denis Filer. 2013. An Atlas of the World's Conifers. Leiden, Netherlands: Brill Academic Publishers.

Jackson, A. B. 1932. The coffin juniper. New Flora & Silva 5:31-34.

Li, N., T. Christian, A. Farjon, and K. Rushforth. 2013. Juniperus recurva var. coxii. The IUCN Red List of Threatened Species 2013. http://dx.doi.org/10.2305/IUCN.UK.2013-1.RLTS.T34142A2847725.en, accessed 2019.06.28.