Species Hierarchy
Common name:


Species Info:

This lifeform is found east of the Continental Divide in North America. The white color will help identify this lifeform.

Pear-thorn (Crataegus calpodendron) is found from central New York west to Minnesota and south to New Jersey, Pennsylvania, and in the mountains to Georgia, and Missouri. This is a shrub or small tree that grows up to 20 feet tall. The leaves are doubly serrate. The fruit is orange or red.

Crataegus genus (Hawthorn trees)  is native to the temperate regions of the Northern Hemisphere with a few species at higher altitudes in Central and South America.  There are perhaps between  200 and 300 small trees and shrubs in this genus.  The alternate leaves are usually lobed or toothed or even somewhat double-toothed.  The small fruits remind one of tiny apples and the branches are usually thorned.  Many of these species grow as small trees in open pastures.  The 1913 version of Britton and Brown observed that over 1,000 species have been described in North America.  This version of Britton and Brown shows 73 species in the area from Kentucky north to Labrador and west to Kansas.  Kartesz shows 166 species and six subspecies growing in greater North America as of 1994.  Consequently,  there are probably many forms that are still open to taxonomic questions.  Also many identifications can be only tentative.  Although there are numerous botanists and nature lovers reseeding wildflowers into various state, county, and city natural areas,  the long term future of many of the species in this genus may be of concern.

Fruit Trees are an important group of plants. They provide  essential foods and vitamins for human consumption. Included in this group are the apple, pear, peach, cherry, plum, prune, quince, apricot, etc.

Rose Family (Rosaceae) of the Rose Order contains the Rose genus and is a very large diverse family containing not only the roses, but many small weeds and also the important fruit trees including the apple, cherry, pear, and plum. Along with the Grass and Legume Families, this family is one of the most important of all plant groups. There are over 3,000 species in this family organized into over 100 different genera. There are over 840 species growing in greater North America. Typical flowers in this family have five petals and five sepals.

Here the family is divided as follows:

A) Miscellaneous small wild plants such as roses, strawberries, et cetera
B) Rose hybrids of interest to the flower gardener
C) Spiraea group (which forms a natural subfamily)
D) Fruit trees and hawthorns, et cetera

Rose Group (Order Rosales) contains many large and very important families. Included here are fruit trees in the family Rosaceae, the nitrogen fixing plants like clover and alfalfa (in the family  Leguminosae), and a large assemblage of plants divided into over fifteen different families.

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 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.

Plant kingdom contains a large variety of different organisms including mosses, ferns, and seed plants. Most plants manufacture their energy from sunlight and water. Identification of many species is difficult in that most individual plants have characteristics that have variables based on soil moisture, soil chemistry, and sunlight.

Because of the difficulty in learning and identifying different plant groups, specialists have emerged that study only a limited group of plants. These specialists revise the taxonomy and give us detailed descriptions and ranges of the various species.  Their results are published in technical journals and written with highly specialized words that apply to a specific group.

On the other hand, there are the nature publishers. These people and companies undertake the challenging task of trying to provide easy to use pictures and descriptions to identify those species.


Search Region:
Species Range:
Click to enlarge
(Click on an image below to display at left)



Quick Jump:
Click to jump to
Backward 10 species
Click to jump to
Backward 1 species
Click to jump to
Forward 1 species
Click to jump to
Forward 10 species