Crataegus sales at

 Sargent's hawthorn (C. sargentii)

 Oneflower hawthorn (C. uniflora)

 Ashe hawthorn (C. ashei)

Excerpt from Chapter 4, Taxonomy of hawthorns:

     The early taxonomy of hawthorns was in simplistic infancy prior to 1899. Major floral treatments of Asa Gray and Alvin Chapman, published between 1857 and 1867, listed only 10 to 14 species and 2 to 4 varieties for eastern North America. To this array, new species and varieties were added by various European and American authors, sometimes based on garden specimens and rather obscurely documented collections, until the genus was composed of about 175 names by 1899. This was the beginning of a trend, as some of these new names represented merely variant forms of highly polymorphic species already named, or yet to be named. The trend would soon accelerate and swell the genus to unmanageable proportions in the next century.

     A period of expansion for the taxonomy of the genus Crataegus began in 1899 when Chauncey Delos Beadle and William Willard Ashe began publishing descriptions of new species from the southeastern U.S. at a rapid rate, working independently. In 1901, Charles Sprague Sargent also began his independent effort in naming new species, mostly from the northeastern and central U.S. Among these three botanists alone, a flood of new names swept the ranks of the genus to over 1000 species by 1910. C.D. Beadle, a Canadian-born botanist working at the Biltmore Estate in Asheville, North Carolina, named 147 hawthorn species between 1899-1902, mostly from Alabama, Georgia, Florida and the Carolinas. W.W. Ashe, working in the North Carolina Geological Survey and later the U.S. Forest Service, contributed 216 hawthorn names (180 species and 36 varieties) during 1899-1932, about 106 of these from the Southeast. C.S. Sargent prolifically named 732 species and 22 varieties during 1901-1922, most while Director of the Arnold Arboretum of Harvard University; 244 of these are from the Southeast. William W. Eggleston, associated partially with the New York Botanical Garden, was also a contributor to hawthorn descriptions and revisions, publishing 13 names by 1910. Nathaniel L. Britton added 10 names during the same period. The pace of new Crataegus names slowed after 1912, except for the continued activities of Sargent and Ashe. During 1925-1962, Ernest Jesse Palmer contributed several new species and many revisions and analytical publications for the genus, preparing keys and taxonomic treatments used in several major floral texts by other authors. Emil P. Kruschke, working as a botanist with the Milwaukee Public Museum, also contributed new names and taxonomic revisions from 1955 to 1965, mostly for Wisconsin and surrounding states. William Murrill described 21 species from Florida in 1942. The most recent authority, James B. Phipps of the University of Western Ontario, began publication of hawthorn research and revisionary work in 1979, including several new species descriptions for Central and North America.

     Today, worldwide, there are approximately 1700 published names in Crataegus, but arguably only 150-200 valid species. Around 1300 names exist for North American hawthorns, with about 597 available to describe the hawthorn complexity of the southeastern U.S. region covered by this book. There are 62 species selected for treatment in this book, with an additional 72 taxa placed as significant varieties, forms and cultivars. Another 72 taxa are considered as putative hybrids or questionable species. Of these 206 names chosen to best represent Southeastern hawthorn diversity, over 70% are illustrated.