Cupressus

Common Names

Cypress (Eckenwalder 1993).

Taxonomic Notes

A genus of 28 taxa, all of which have been described as species but many of which have been reduced to subspecies or varieties on debatable grounds. The large range of opinion occurs because cypresses generally occur in small isolated populations distinguished by small differences, interpreted by some as valid at species rank, but by others only at varietal or subspecific rank. Analyses performed in the 1990s using morphological and chemical data (e.g. Eckenwalder 1993, Frankis 1992, Farjon 2005) tended to "lump" taxa into a relatively small number of species (as few as 12). Conversely, the more narrow species concept was early advocated by Wolf (1948) in his monograph on the New World cypresses and was later supported by Rushforth (1987) and, for the California species, by Lanner (1999). A more recent analysis using morphological, chemical and multiple lines of molecular/genetic data (Little 2006) found that many of the isolated populations are sufficiently distinct to be regarded as discrete species. Those findings are summarized in the cladogram shown here.

I have chosen, on the basis of these findings, to recognize certain taxa as good species, while retaining others as subspecies or varieties. The close relationship between the varieties of C. goveniana appears to be well supported, and is here retained. However, taxa that have been treated as varieties of C. arizonica in recent treatments (Eckenwalder 1993, Farjon 2005) all may warrant species rank, or more particularly, may be more closely related to other species (such as C. lusitanica and C. guadalupensis) but have not yet been so described. A similar problem applies to C. forbesii, formerly treated as a variety of C. guadalupensis but now seeming to be just as closely related to C. stephensonii. Indeed, these taxa represent a significant, persistent taxonomic problem that dogs the taxa here treated as C. arizonica, C. benthamii, C. forbesii, C. guadalupensis, C. lusitanica, C. montana, C. nevadensis and C. stephensonii: namely, that all of these taxa appear to represent a species complex rooted in northwest Mexico, an area which has not been adequately studied. Fully understanding how these taxa are related, and whether any of them can be meaningfully distinguished as separate species, awaits comprehensive study of the many geographically distinct Cupressus populations in this vast desert range.

Little (2006) has also proposed, with strong support from molecular/genetic data (cf. Little et al. 2004), that Cupressus be divided into new world and old world genera. The new world species, which are more closely related to Juniperus than to the old world species, he assigns (along with both species of Xanthocyparis) to the new genus Callitropsis Oersted; while the old world species remain in Cupressus L. This is a very recent proposal that has not yet received critical review in the taxonomic community. The proposed nomenclatural changes are as follows:

Table. Proposed changes in nomenclature: Cupressus and Xanthocyparis.
Current name	Proposed name
Cupressus goveniana var. abramsiana	Callitropsis abramsiana
Cupressus arizonica	Callitropsis arizonica
Cupressus bakeri	Callitropsis bakeri
Cupressus benthamii	Callitropsis benthamii
Cupressus forbesii	Callitropsis forbesii
Cupressus glabra	Callitropsis glabra
Cupressus goveniana var. goveniana	Callitropsis goveniana
Cupressus guadalupensis	Callitropsis guadalupensis
Cupressus lusitanica	Callitropsis lusitanica
Cupressus macnabiana	Callitropsis macnabiana
Cupressus macrocarpa	Callitropsis macrocarpa
Cupressus montana	Callitropsis montana
Cupressus nevadensis	Callitropsis nevadensis
Xanthocyparis nootkatensis	Callitropsis nootkaensis
Cupressus goveniana var. pigmaea	Callitropsis pigmaea
Cupressus sargentii	Callitropsis sargentii
Cupressus stephensonii	Callitropsis stephensonii
Xanthocyparis vietnamensis	Callitropsis vietnamensis
Cupressus atlantica	Cupressus atlantica
Cupressus cashmeriana	Cupressus cashmeriana
Cupressus chengiana	Cupressus chengiana
Cupressus duclouxiana	Cupressus duclouxiana
Cupressus dupreziana	Cupressus dupreziana
Cupressus funebris	Cupressus funebris
Cupressus gigantea	Cupressus gigantea
Cupressus sempervirens	Cupressus sempervirens
Cupressus torulosa	Cupressus torulosa

The situation has been further complicated by a decision on the part of the IBCN Committee on Spermatophyta to conserve the name Xanthocyparis against Callitropsis. The decision, proposed for publication in Taxon late in 2007, confirms that all of the Callitropsis taxa identified in the foregoing table will have to be published as taxa of Xanthocyparis in order to be valid names. At this time, those combinations have not yet been published.

If this is not sufficiently confusing, check back in a year or two.

Despite the relatively large genetic distance between Cupressus and Chamaecyparis (Brunsfeld et al. 1994, Gadek and Quinn 1993, Gadek et al. 2000), delimitation of these two often superficially very similar genera has been subject to extensive dispute. C. funebris in particular has been moved back and forth repeatedly, with the most recent chemical and phenological evidence (Farjon 1998, Rushforth 1987) showing it to belong in Cupressus.

Perhaps surprisingly, the closest genetic relative of Cupressus is Juniperus, with Platycladus and Microbiota also close (Gadek and Quinn 1993, Brunsfeld et al. 1994).

Description

Trees or large shrubs, evergreen. Branchlets terete or quadrangular, in decussate arrays in most species; flattened (comblike), superficially resembling Chamaecyparis or Thuja in others. Leaves opposite decussate in 4 ranks, rarely in alternating whorls of 3 in 6 ranks. Adult leaves appressed to divergent, scalelike, rhomboid, free portion of long-shoot leaves to 4 mm; abaxial gland present or absent. Pollen cones with 4-10 pairs of sporophylls, each sporophyll with 3-10 pollen sacs. Seed cones maturing in (?1-)2 years, exact maturation period poorly researched, mostly varying from about 16-25 months after pollination; generally persisting closed many years or until opened by fire, but opening on maturity, and falling soon after seed release, in a few species; globose or oblong, 8-43 mm; scales persistent, (2)3-6(7) opposite decussate pairs, valvate, peltate, thick and woody, the terminal pair either fused or open with a small central columella (varying from cone to cone on a single tree). Seeds (3)5-20 per scale, lenticular or faceted, narrowly 2-winged; cotyledons 2-5. x= 11 (Eckenwalder 1993, Frankis 1999).

Range

Warm north temperate regions (Eckenwalder 1993): W USA, Mexico and adjoining Central America, NW Africa, Middle East and eastward along the Himalaya to SW & Central China and N Vietnam.

Big Tree

There are no good data for a variety of species, but of the documented ones, Cupressus gigantea seems the clear winner, followed by Cupressus macrocarpa.

Oldest

There are few age data on Cupressus in general. Based on habitat (trees native to desert mountains tend to live a very long time), I suspect C. dupreziana (Frankis 1999) may attain great ages.

Dendrochronology

Several species have proven useful in climate reconstruction, archeological dating, and ecological studies. The genus appears to be less intractable than most of the Cupressaceae with regard to such problems as poor ring boundaries, false rings, and poor circuit uniformity. See the individual species for details.

Ethnobotany

Several species are of horticultural importance; fastigiate forms of C. sempervirens, C. duclouxiana and C. funebris have been cultivated for ornament for several thousand years in the Mediterranean region and S China respectively, and the highly decorative weeping C. cashmeriana similarly long around Buddhist temples in Sikkim, Bhutan, Assam and nearby areas of Tibet and India.

The wood is valued for its sweet scent and resistance to decay. Famous uses of the wood (of C. sempervirens) include Noah's Ark (The Bible, Genesis 6:14), and the doors to St. Peter's, Vatican City, Rome, which were still sound after 1,100 years' use (Loudon, 1838; reference misplaced).

Observations

Remarks

The genus name is from the Roman name for C. sempervirens, itself a loan word via Greek Kuparissos from Hebrew Gopher (Frankis 1992).

Citations

Frankis, M.P. 1992. Cupressus. In: Griffiths et al. (eds) The New RHS Dictionary of Gardening 1: 781-783.

Frankis, M.P. 1999. Contributions based on personal experience, via e-mail, 1999.02.03.

See Also

The Cupressus Conservation Project provides a wealth of information on old and new world Cupressus, including a taxonomic review, historical accounts, cone photographs, and various other pertinent information.

Farjon (2005) provides a detailed account.

Goggans, J.F. and C.E. Posey. 1968. Variation in seeds and ovulate cones of some species and varieties of Cupressus. Circ. Agric. Exp. Sta., Alabama 160:1-23.

Little 1966.

Little 1970.

Masters, M.T. 1896. A general view of the genus Cupressus. Journal of the Linnaean Society, Botany 31: 312-363. http://www.cupressus.net/Masters.html, courtesy of the Cupressus Conservation Project website.

Silba 1981.

Silba, J. 1998. A monograph of the genus Cupressus L. Journal of the International Conifer Preservation Society 5(2):1-98.

Wolf 1948.

This page co-edited with M.P. Frankis, Feb-1999.