[From Volume 1: Introduction]

Nancy R. Morin
Richard W. Spellenberg

The Flora of North America project has grown out of a long history of interest in the flora area and has built on the experiences of previous efforts to produce a comprehensive flora. It has been designed to draw on the expertise of the entire systematic botany community and to make the best possible use of the literature and herbarium specimens that are essential resources for the project. Despite current interest in and urgency of botanical studies of many other kinds, there continues to be a need for information about the plants of North America on a continental scale.

Historical Background

The Flora of North America project derives from the deep interest that botanists have in studying and characterizing the plants of the region and the need for authoritative information for basic and applied research, conservation, and resource management. Ever since explorers first sent North American plants to Europe, the world has known that the flora is rich and interesting. The first accounts of plants from the area were published in Europe by European botanists (e.g., in Robert Morison's Historiae [1680--1699], Leonard Plukenet's Phytographia [1691--1705], and John Ray's Historia Plantarum [1686--1704]). Fredrick Pursh's Flora Americae Septentrionalis (1814) was the first flora of continental scope. Treatises on North American plants were written by resident botanists in the early 1800s, and the first attempt at production of a comprehensive flora of the continent was undertaken by John Torrey and Asa Gray the 1830s (see J. L. Reveal and J. S. Pringle, chap. 7). Subsequently, botanists focused on producing regional floras, until 1905 when N. L. Britton began publishing the monographic series North American Flora at the New York Botanical Garden.

Flora North America, 1965--1973

Because regional floras do not provide fully comparative information on plants throughout their ranges, the potential utility of a continental flora is self-evident. Recognizing the need and spurred, at least in part, by the announcement at the Tenth International Botanical Congress in Edinburgh in 1964 that volume 1 of Flora Europaea (T. G. Tutin et al. 1964--1980) was soon to be published, North American botanists considered launching a comprehensive flora project at home. At the annual meeting of the American Institute of Biological Sciences (AIBS) in August 1964, the Council of the American Society of Plant Taxonomists (ASPT) appointed a committee to study the feasibility of undertaking the production of a flora of North America.

This committee of about 25 interested botanists was chaired by Robert F. Thorne, and it met in Washington, D.C., in May 1966. The committee concluded that production of a flora of North America was both desirable and feasible. Thorne, on instructions from the committee, corresponded with many botanists about their willingness to serve in some capacity on the flora project. The response was overwhelmingly positive and left no doubts as to the advisability of proceeding.

In August 1966, during the meeting of AIBS at the University of Maryland, the Council of ASPT voted to sponsor the flora project, to be called "Flora North America," and designated an organizational committee under the chairmanship of Mildred E. Mathias. Mathias drew up an organizational structure in which the Smithsonian Institution served as the project headquarters. Steering and editorial committees were appointed, and the organizational committee was disbanded.

In 1967 sponsorship of the project was transferred to AIBS. The National Science Foundation awarded two grants---one from the Systematic Biology Program and one from the Information Systems Program, Office of Science Information Service---to AIBS in July 1969 to support planning for the project. The grants provided for a small central staff at the Smithsonian Institution and for travel by members of the planning committees. By 1969 automated data processing had assumed major importance, and part of the planning grants funded a systems development manager. Peter H. Raven, chairman of the editorial committee, was program director. Stanwyn B. Shetler was program secretary, and devoted nearly full time to the daily activities of the program.

Pilot projects were developed to define the Flora North America databanking approach. The biological community was canvassed by use of several questionnaires designed to identify potential users of the databank, to inventory plant systematists, and to evaluate systematists' interests and potential as contributors. Pilot databanks included the Type Specimen Register, which comprised 7000 records at the end of 1971, and "authority files," such as an author file, a higher taxon list, a species name list, a contributor file, and a morphological/ecological vocabulary. B.R. Rohr et al. (1977) provided a comprehensive account of publications resulting from the Flora North America program.

In 1971 a program council was formed to act as the single body charged with advising the administering institution (then AIBS) regarding policy. The program council recommended that the Smithsonian Institution become the administering institution, taking that responsibility from AIBS with the latter's full approval. This transfer took place in July 1971. The Secretary of the Smithsonian Institution made a commitment to the National Science Foundation that the Smithsonian Institution would share in the costs for the project and would maintain the database indefinitely.

A proposal was submitted to the National Science Foundation in 1971 requesting funds for the implementation of the project. Similar proposals were submitted to the Canada Department of Agriculture and the National Research Council of Canada. The funding, which was approved, was to support seven regional editorial centers in Canada and the United States, and the headquarters and systems development center at the Smithsonian Institution.

After six years of planning, the project became operational in the fall of 1972. National Science Foundation support was made contingent on the willingness of the Smithsonian Institution to increase its funding year by year, and their commitment to do so. Examining its overall priorities, the Smithsonian Institution decided that it was unwilling to make such a guarantee, unless Congress would in turn guarantee that the institution's total request would be funded each year. Consequently, the National Science Foundation felt obliged to withdraw its support, and the project was suspended in the summer of 1973. Attempts to revive the project through collaboration with the Man in Biosphere project and the National Park Service were not successful.

The Flora of North America Project


In spring 1982, 22 botanists from throughout the United States and Canada met at the Missouri Botanical Garden to consider a plan proposed by the Hunt Institute for Botanical Documentation and the Carnegie Museum to resume collaborative preparation of a flora of North America north of Mexico. In the new plan, a significant portion of the project costs, particularly staff time and use of facilities, would be contributed by participating institutions, and the flora would consist of traditional treatments prepared by members of the systematic botanical community. Information from the treatments would be used to develop a databank. That meeting was the basis for the formation of the current Flora of North America project.

A steering committee was appointed by those attending the 1982 meeting in St. Louis. The steering committee met at the Hunt Institute in January 1983 and determined that a proposal detailing the project should be written and submitted to the American Society of Plant Taxonomists and the Canadian Botanical Association/L'Association Botanique du Canada for endorsement.

At the annual ASPT Council meeting in August 1983, the Missouri Botanical Garden offered to serve as the organizational center for the multi-institutional, collaborative project and offered staff assistance for preparation of the proposal and for continued organization of the project. Administrators from several of the larger North American botanical institutions were subsequently invited to serve on an advisory panel, and an editorial committee was established. Representatives of the home institutions of the editors, and of other institutions supporting the project, each signed a memorandum of cooperation and together they established the Flora of North America Association.

To help establish the Flora of North America project, the advisory panel counseled project members about organization and implementation from the standpoints of both the systematic botanical community at large and their own institutions. The original advisory panel fulfilled its purpose and was disbanded in November 1989.

Community support for the project was voiced in 1982, when the Canadian Botanical Association/L'Association Botanique du Canada passed a resolution reaffirming its commitment and approving the steps being taken to produce a flora of North America. Further, at its annual meeting in August 1983, the American Society of Plant Taxonomists passed a resolution affirming its commitment for production of such a flora.

The Organizational Years

From 1983 to 1987, when outside funding was first acquired, the project was supported entirely by participating institutions. Missouri Botanical Garden contributed staff time and facilities for the organizational center and sought funding on behalf of the project. Proposals for funding were submitted to the National Science Foundation and to private foundations. The editorial committee used this time to identify and contact potential contributors and reviewers for taxa in the first volumes, to determine what should be included in the treatments and database, to write sample treatments, and to develop a "Guide for Contributors." In February 1988 the Pew Charitable Trusts awarded a matching grant to the project; that funding made it possible for the editorial committee to meet and for the organizational center to hire support staff for the project. A year later, matching funds were received from the National Science Foundation.

Filling the needs of users who are not botanists or systematists for authoritative information on plants has been a major goal of the project. A workshop, "Floristics for the 21st Century," was organized to define these needs and to discuss how these needs could be met. The workshop, supported by the National Science Foundation, met in Alexandria, Virginia, in May 1988, with some 70 biologists from around the world and from a variety of disciplines in attendance. The proceedings were published the following year (N.R. Morin et al. 1989).

Until 1990 Flora of North America was scheduled to include only vascular plants. At the annual meeting of the American Society of Bryologists in December 1990, members agreed to prepare treatments for a bryophyte volume of the flora. Bryologists were added to the editorial committee for this purpose and started work in 1991. Flora of North America, therefore, will treat all embryophytes growing without cultivation in North America north of the United States – Mexico boundary.

Project Organization

In order to synthesize existing knowledge concerning the vascular plants of North America, the project has attempted to identify and draw on the expertise of the entire systematic botanical community. In addition to plant taxonomists in North America and other parts of the world, biologists in the various governmental agencies help the project directly by reviewing and sometimes contributing treatments and indirectly by providing their expert knowledge to those who are preparing treatments.

The editorial committee is the governing body of the Flora of North America project. It consists of (1) taxon editors, each of whom is responsible for soliciting and editing treatments of blocks of families; (2) regional coordinators, each of whom acts as liaison between the project and the botanical community in his or her region; (3) a bibliographic editor; (4) a nomenclature advisor; and (5) a convening editor, who has ultimate responsibility for the coordination, quality, and completion of the project. Special advisors with expertise in specific areas, such as economic uses or conservation, have been asked to join or assist the editorial committee, and others may be added before the project is completed.

Almost all of the treatments are written by specialists in the groups. Treatments for which no specialists are available are written by project staff or other botanists. Reviewers who are particularly knowledgeable about given geographic regions or taxa critique treatments of species that occur in their areas or that fall within their taxonomic expertise.

Flora of North America Databases

The original Flora North America project had the clear vision that computerization could make floristic work easier and more valuable. In addition, participants at the "Floristics for the 21st Century" workshop, held in 1988, identified many potential users of Flora of North America information. In order for floristic information to be useful to this large audience, however, it must be easily accessible in a variety of ways. Computerized databases allow access to and analysis of the many kinds of information contained in floristic treatments. A botanical database for the Flora of North America project was established at the Missouri Botanical Garden using the TROPICOS system developed at the Garden. In 1989 a computer databases consultant group was instituted to discuss the long-term computerization needs of the project, and its recommendations helped to improve the system. The TROPICOS database uses plant names to link information on features such as relationships, distribution, characteristics, and specimens. Data from other wide-area floristic projects, such as Flora of China and Flora Mesoamericana, connect to Flora of North America data, allowing comparisons of distributions and features on a broad geographic scale.

Production of the database proceeds simultaneously with the preparation of the hard-copy flora. The database will eventually contain all the information found in the published volumes as well as additional information, such as more detailed morphological data, information on type specimens, and documentation for chromosome counts. Furthermore, it will also incorporate information on habitats, precise distributions, populations, and plant communities. Morphological descriptions are recorded as characters and character states in a way that allows searches for character states or suites of character states, and permits various other kinds of analyses. The database is online, and additional information about it and access to it are available from the Flora of North America organizational center at Missouri Botanical Garden.

All references used in the published volumes are entered into a computerized database at the Hunt Institute for Botanical Documentation. This database will allow searches of published sources and will be used to produce bibliographies in the individual volumes and to produce the cumulative bibliography.

In order to provide comprehensive information to Flora of North America contributors, reviewers, and editors, the project maintains files on plant systematists, floristic and taxonomic databases, relevant references, and unpublished studies. These resources, coupled with the ever-building database on North American plants, give the project the ability to act as a referral service providing information on North American floristic studies, references, and specialists.

Resources for Flora of North America

Flora of North America treatments are based on critical evaluation of the literature, examination of specimens, and field and laboratory experience. Most contributors and reviewers have studied the plants in the field, and such firsthand experience adds to the quality of the treatments. Information derived from recent experimental work and numerical taxonomy is also incorporated into the treatments.

In the preparation of manuscripts, authors have either examined specimens from herbaria to determine morphological variation and geographic distribution, or they have used recent monographs and revisions, which in themselves are the results of critical examination of specimens. Whether a manuscript has been generated from a fresh look at specimens or primarily from review of critical revisions, specimens have been used by authors to test the work, and they have been examined by reviewers to determine accuracy of descriptions, usability of keys, and correctness of stated geographic ranges.


Taxonomic work depends to a great extent on information recorded in the literature. Original descriptions of taxa, many of them dating from the early 1700s, must be consulted in order to determine the correct application of scientific names. Monographs and revisions contain information about the taxa themselves and about the taxonomic opinions of those who studied them. Shorter reports contain additional information about the biology and distribution of the taxa. Local and regional floras may contain detailed information about the morphology and distribution of taxa within the specific regions that they cover.

Many major regional floristic works have been published in the past three decades. For Canada, examples include: H.J. Scoggan, The Flora of Canada (1978--1979); A.E. Porsild and W.J. Cody, Vascular Plants of Continental Northwest Territories, Canada (1980); and E.H. Moss and J.G. Packer, Flora of Alberta (1983).

Similar projects in the United States include: Vascular Flora of the Southeastern United States (A.E. Radford et al. 1980+); Flora of the Great Plains (Great Plains Flora Association 1986); Intermountain Flora: Vascular Plants of the Intermountain West, U.S.A. (A.Cronquist et al. 1972+); Vascular Plants of the Pacific Northwest (C. L. Hitchcock et al. 1955--1969); Manual of the Vascular Plants of Texas (D.S. Correll and M.C. Johnston 1970); and The Jepson Manual: Higher Plants of California (J.C. Hickman, ed., 1993).

This literature has been made available to Flora of North America participants by university, museum, and botanical garden libraries either directly or through interlibrary loans. Without this considerable assistance from libraries and librarians, the project would be virtually impossible to complete.


Flora of North America is primarily specimen-based. Plant specimens are generally pressed and dried after they have been collected. Information is recorded about where the plant was collected, and additional information about the habitat or species associated with the plant may be included. The pressed specimens are mounted on paper with a label containing the recorded information. They are then stored in herbaria, where they are given protection from pollutants, moisture, destructive insects and rodents, and careless handling. Given proper protection, such specimens last indefinitely and provide a wealth of historical information.

Specimens have been made available to Flora of North America participants directly, or as loans. Thus it has been possible for an author to study together all collections of a particular taxon made through time and throughout its range. In some cases curators have provided information recorded on labels to confirm reported distributions, morphological features, and dates of flowering or fruiting. Much of what is known about the historical floristic diversity of North America is based on information held in herbarium specimens. Specimens have provided a picture through time of the changes in distribution of a taxon, sometimes of the rate and pattern of spread of a noxious plant, but more often of the collapse of the geographic range of a taxon through the influence of human activity. In a few instances, specimens are the only indication that an extinct taxon once existed.

Herbarium specimens document much of the information reported in Flora of North America North of Mexico and the database. Authors have annotated specimens they examined in preparation for writing the treatments. Documentation is maintained on specimens from which illustrations were drawn. Herbarium specimens serve as vouchers for chromosome reports. Much of the experimental work mentioned in the discussion sections is documented by herbarium specimens or has used herbarium specimens as a source of material.

There are more than 60 million specimens in 628 herbaria in the United States and nearly 7 million specimens in 110 Canadian herbaria; a small local collection of specimens exists in the herbarium in Greenland. The oldest existing herbarium in the United States is at Salem College, Winston-Salem, North Carolina, established in 1771; the oldest in Canada is the Royal Ontario Museum, Toronto, Ontario, established in 1838 (P.K. Holmgren et al. 1990). Table 1 lists the largest herbaria of the United States and Canada, with the date of establishment and number of specimens. Of the nearly 273 million herbarium specimens in the world, 25% are held in institutions in the United States and Canada. Many specimens from North America are located in European herbaria, particularly the Natural History Museum in London; Royal Botanic Gardens, Kew; the Muséum National d'Histoire Naturelle, Paris; Conservatoire et Jardin botaniques, Geneva; Liverpool Museum, Liverpool; and the University of Copenhagen, Copenhagen.


Flora of North America is an enormous undertaking, but the accumulation of data from monographic studies and regional floras has contributed so much that the time to attempt the kind of overall synthesis envisioned by Torrey and Gray more than 160 years ago is now clearly at hand. Flora of North America distills and synthesizes information found in monographs and revisions, and makes it more easily accessible to ecologists, plant morphologists and physiologists, zoologists, conservationists, and workers in many other scientific disciplines. The flora also brings together information about the characteristics, relationships, distribution, and biology of all of the vascular plants and bryophytes of North America north of Mexico so that it can be used as a basis for further studies of all kinds. Such information is indispensable for the proper management, scientific study, and conservation of the plants of North America.

Identification of individual plants is essential to most kinds of botanical research, including agriculture, horticulture, forestry, and plant conservation. Local and regional floras and other specialized guides will continue to be the principal means of identifying plants, but the taxa they treat can be understood in a regional context only by means of a work such as the Flora of North America North of Mexico. Such a flora can also serve well for the identification of plants found for the first time beyond their known ranges, and thus not included in regional works. Flora of North America also synthesizes the important regional floristic work and results of exploration of little-known areas currently underway in North America.

A continental flora provides a catalog of the plant resources available within the area and their status — it can be used as a gauge to assess environmental change and as a tool to help manage resources in the future. Flora of North America, with its printed volumes and online database, will provide information for many essential purposes.