This lifeform is found widely in Africa. This lifeform is found widely in Eurasia. This lifeform is found widely in the Indo-Australian region. This lifeform is widespread in North America. This lifeform is found widely in the New World tropics. This lifeform is grown commercially for human food. This lifeform is very common in suitable environments.

Oats (Avena sativa) is a well-known and very important agricultural crop. This species normally has spikelets with only two flowers.

Avena genus (oats) is native to northern Africa and Eurasia.  There are about 15 species of annual herbs in this genus.  The spikelets have two or three  flowers.  There are six species now established in greater North America.  Cultivated oats (A. sativa) is one of the world's most important food crops.  Wild oats (A. fatua and A. barbata) are common in western North America and are used for hay. The Algerian oat and the red oat  (both derived from A. sterilis) are also important grains.

Aveneae Tribe is best known for oats.

Grass family (Gramineae to Poaceae) is a worldwide family of greatest economic importance.

Important plants, such as wheat, oats, corn, and rice, are found in this family. Mr. A.S. Hitchcock's two-volume Manual of the Grasses, revised by Agnes Chase, is recommended for the serious student of the grasses of the United States. Identification of grasses is difficult and a unique special vocabulary has developed to study this family. (Awns, glumes, lemmas, etc are some of the words most frequently used.)  The grasses are usually divided into several tribes to facilitate their study. Tribes in this reference are outlined according to Hitchcock.

Glumiflorae are a group of Monocots that contain the grasses and the sedges. (The similar-looking rushes, which are more closely related to the lilies, are usually not placed here.)

Monocots are a large group of plants usually characterized by having leaves with parallel veins and a seed with a single shell. Most flowers are created with multiples of three. In  the older botany texts, the Monocots were considered more primitive than the Dicots. However, many recent authors have placed the Monocots as an offshoot of the primitive Dicots. Here they are placed before the Dicots.

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.