This piece presents a brief review of the literature on gymnosperms. The principal motivation for this review is simply that the Gymnosperm Database cannot present in-depth, or in many cases even very current, treatment of all gymnosperm taxa. This is because our knowledge of this group is so vast, and is increasing so rapidly, that as the years go by I find that increasingly I am merely maintaining a library of links that point to information, rather than presenting the information per se. Merely as an illustration, the backlog of digital data that is currently waiting to be assimilated to the Database now stands at 588 megabytes, not counting a couple thousand pages of printed matter standing by. In contrast, the online Database comprises 65 megabytes, and it has taken seven years to get all that online.

The purpose of this review, then, is to provide you with some guidance about where to go to get survey-level information about all gymnosperm taxa. I must caution you that many of the required documents are hard to come by, usually requiring access to a major research library. The difficulty of acquiring these documents was one of the things that drove me to develop the Database in the first place. Nonetheless, here they are. I will first review the few recent works that address all conifers, all cycads, or at least a large variety of gymnosperm species. I will then review the major regional works addressing areas with high native gymnosperm diversity. This review will focus on printed literature, although some of these sources are also available online. However, you should review the Links page for most sources of online information. You may also want to peruse the Bookstore page for those works that are still in print.

Generally, I do not list works published before 1950. This is not to disparage earlier authors or imply that their contributions are unimportant; rather, it is simply tacit recognition of the fact that newer literature better reflects current taxonomic concepts, is often more accurate, is usually more accessible, and in any event cites the older works. In this connection, the outstanding conifer bibliography (at least, for the Pinaceae and Cupressaceae) is that prepared by Farjon (1990) (updated in 2005, perhaps available online in 2006), while both Whitelock (2002) and Jones (1993) offer less encyclopedic but nonetheless significant bibliographies for the cycads. For ginkgo and the gnetophytes, there is no dedicated bibliography that I know of.

Major Review Works

Dallimore et al. (1967), although aimed primarily at the British horticultural audience, is still a reasonably current work with consistent, useful descriptions. It is probably still the first work to consult if you want to see all conifers described between two covers. However, for virtually every species, there are better works available; and the taxonomic treatment was a bit hoary even in 1974, reflecting the book's heritage (the first edition appeared in 1923).

Vidakovic (1991) treats all conifer species known at the time, although the level of detail is very uneven; in general, conifers currently grown in eastern Europe are treated exceptionally well, while those native to the southern hemisphere receive the least detail. For the best-described species, he offers not only descriptions but photographs, drawings, maps, descriptions, ecological and ethnobotanical information, and sometimes even a bit of pathology.

Silba (1986, 1990) also offers an encyclopedic treatment of worldwide conifers, but should be read with a grain of salt because he has proposed many taxonomic revisions that have not won subsequent acceptance. Also, Silba's treatment of most taxa is cursory in the extreme.

Z. Debreczy and I. Rácz are about to (2006) publish Conifers around the world a semi-encyclopedic work covering all conifers hardy in temperate climates. I believe this is an updated and expanded version of their Hungarian text that was published a few years ago, and if so, it should be very well illustrated by color photos, with good descriptions and quantitative climatic information. It will be available from Dendropress.com.

Two other comprehensive works of particular interest to horticulturists are Rehder (1962), with excellent descriptions; and Van Gelderen and Van Hoey Smith (1986), with hundreds of color photographs (mostly taken in gardens, but some in habitat). These two works also discuss artificial cultivars, which are not addressed at all in the Gymnosperm Database.

The "World Checklist and Bibliography of Conifers" (Farjon 1998, with a second edition released in 2005) is the one conifer book that never seems to make it back onto my shelf. It has no species descriptive information (except "tree" or "shrub") and very little about species distribution, but is an invaluable reference on taxonomic nomenclature. It also lists the conservation status of each taxon, as determined by the IUCN Conifer Specialist Working Group (a subject further detailed by Farjon and Page [1999]).

Farjon (1984 [2nd ed. 2005]) and Farjon (1990) together constitute a complete treatment of the Pinaceae. Both volumes are very well illustrated with the author's line drawings and both present significant, largely still-current information on the taxonomy, morphology and ecology of each taxon treated. Farjon (2005) reprised this performance with the publication of a massive, exquisite monograph on the Cupressaceae and Sciadopityaceae. I know of no other comprehensive treatments of conifer families (though Farjon tells me he'll probably have one on the Araucariaceae in a few years), but the works be de Laubenfels discussed below effectively cover large parts of the Podocarpaceae.

Richardson (1998) also deserves mention, as one of the few comprehensive treatments (of all species in Pinus) that is not focused on description or taxonomy. Rather, the focus is on ecology, natural history, and human use of the species. Also, for the genus Pinus, Mirov (1967) gives a wonderfully detailed treatment of every species known at the time, while Critchfield and Little (1966) present outstanding range maps for most species in the genus. Also see Prasad and Iverson (1999) [which is available online] for some very modern and sophisticated range maps of most widespread North American species.

As noted above, Whitelock (2002) presents the most comprehensive treatment of the Cycadales, presenting information on every species and in nearly every case complementing his descriptions with color photographs and ecological information. A series of appendices provide useful horticultural information as well. The second edition of Jones (1993) is also very good.

For the Gnetales, I am not aware of any good recent treatments. My standard is Pearson 1929, which is archaic. There's a good survey of the Ephedraceae by Stevenson (1993), and the many Chinese species are described in Wu and Raven (1999). For the Gnetaceae, the best treatment I know of is by Maheshwari and Vasil (1961), which is sorely dated and in any event is heavily focused on fine anatomical details of a few salient species. More current taxonomic information can be gleaned from the works on wood anatomy by Carlquist (1996a, 1996b). For the Welwitschiaceae, and also for the monotypic order Ginkgo, I know of no more comprehensive recent source than this web site.

Major Regional Works

North America and China are large areas that together command a large fraction of total gymnosperm diversity, especially in the Coniferae and Ephedraceae. Excellent current descriptions of these taxa are presented the Flora of North America (1993) and the Flora of China (1999). The Flora of Australia (1998), Flora of Japan (1995), and Flora of New Caledonia (1972) cover three more areas of high gymnosperm diversity, although the New Caledonia flora is only available in French (it is slowly being translated and published on the Gymnosperm Database, though), and each of these floras only provides descriptive information, with very little ecology or ethnobotany. For New Zealand, Salmon (1996) provides a superb resource, with good descriptions supplemented by copious high-quality color photographs and additional information on each species' natural history. De Laubenfels (1988) covers the highly diverse conifer flora, dominated by Podocarps, of the vast area from the Malay Peninsula east to Fiji and from the Philippines south through New Guinea. These southern hemisphere reviews are nicely augmented by an outstanding text on the "Ecology of the Southern Conifers" by Enright and Hill (1990). Farjon and Styles (1997) and Perry (1991) provide very thorough treatment of the Mexican and Central American pines, while Farjon's monographs (1990, 2005) on Pinaceae and Cupressaceae, mentioned above, must serve for most of the other Mexican and central American conifers, and there is no good regionally-focused treatment of the Central and South American conifers and gnetophytes in general. For the cycads, the best work on the area is again Whitelock (2002).

For most of the rest of the world, published floras are not in English, or are antiquated, or only address a handful of gymnosperm species. Useful examples of the latter are Palgrave (2002) for South Africa and FIPI (1996) for Vietnam. I have had the greatest difficulty finding information for species native to tropical Africa, tropical South America, and the former U.S.S.R., where most of the literature is not in English and I have been forced to depend on the generosity of correspondents who serve as translators. In fairness, though, I have not researched the literature on such species with complete industry, as there is a huge backlog of material on better-known species that is also waiting to be assimilated.