Narrative

Although the western cottonwood is considered a subspecies of the eastern North American Populus deltoides (Populus deltoides variety occidentalis to Populus deltoides monilifera) one can easily get confused. Most related nursery stock sold in western North America as Populus deltoides was actually a cross between Populus deltoides and Populus nigra which was commonly called Populus canadensis.

Populus genus (Poplars) is a well-known genus of about 30 to 35 species of trees that are native to the northern hemisphere. Poplars are typically fast growing and their wood is of little commercial value. Included in this genus are the aspens, poplars, and cottonwoods. Kartesz lists 12 species, 12 hybrids, and seven subspecies as being native to his greater North America, which includes the United States, Canada, Hawaii, Greenland, Puerto Rico and the U.S. Virgin Islands.

Within the Willow and Poplar Family (Family Salicaceae) there are two genera. The wood of all the species in this family is not very strong, and is not of much economic importance. The wood can be made into charcoal, and the thin twigs of some species are used in weaving baskets. Willows (Genus Salix) are a complicated group of trees and bushes that seem to defy any easy system of recognition. This is compounded by the fact that natural hybrids occur.

Willow and Poplar Order (Salicales) has only one family.

Dicots (Dicotyledoneae Class) are the predominant group of vascular plants on earth. With the exception of the grasses (Monocots) and the Conifers (Gymnosperms), most of the larger plants that one encounters are Dicots. Dicots are characterized by having a seed with two outer shell coverings.

Some of the more primitive Dicots are the typical hardwood trees (oaks, birches, hickories, etc). The more advanced Dicots include many of the Composite (Aster) Family flowers like the Dandelion, Aster, Thistles, and Sunflowers. Although many Monocots reach a very high degree of specialization, most botanists feel that the Dicots represent the most advanced group of plants.

Seed plants (Phylum Embryophyta) are generally grouped into one large phylum containing three major classes: the Gymnosperms, the Monocots, and the Dicots. (Some scientists separate the Gymnosperms into a separate phylum and refer to the remaining plants as flowering plants or Angiospermae.)

For North American counts of the number of species in each genus and family, the primary reference has been John T. Kartesz, author of A Synonymized Checklist of the Vascular Flora of the United States, Canada, and Greenland (1994). The geographical scope of his lists include, as part of greater North America, Hawaii, Alaska, Greenland, Puerto Rico, and the Virgin Islands.

Kartesz lists 21,757 species of vascular plants comprising the ferns, gymnosperms and flowering plants as being found in greater North America (including Alaska, Hawaii, Greenland, Puerto Rico and the Virgin Islands.

There are estimates within the scientific world that about half of the listed North American seed plants were originally native with the balance being comprised of Eurasian and tropical plants that have become established.