The continent of North America is home to a wide range of trees, shrubs, flowers and other types of vegetation. It contains most of the main land biomes that are found worldwide, including taiga, tundras, grasslands, deserts and temperate forests. On the other hand, because North America isn't centered in the tropical zone and lies in the temperate zone, there are no tropical forests and savannas.
North American plants are grouped into five categories. Primitive plant species include ferns, alga, horsetails, spikemosses and qillworts. Woody plants, including bushes, shrubs and trees, are plants supported by a woody core with one or more above-ground permanent stems that stay above ground in winter. Rushes and sedges typically contain solid, triangular stems, pointed leaves and flowers borne in spikelets, which resemble spikes. They generally have linear leaves, round stems and inconspicuous flowers. Grasses belong to the Poaceae family and have small insignificant-looking flowers, narrow leaves and hollow stems where foliage is attached. Forbes, which are flowering plants, have broad leaves with nonwoody, green stems.
The North American continent has roughly 20,100 plant species, according to Harvard University. Of these 20,100 plants, about 21 percent are considered endemic. Endemic plants are native floras that only grow in a particular region, such as the Death Valley Monkey Flower, which only grows in Death Valley National Park, notes the U.S. National Park Service website.
North America is the third largest continent and includes the United States, Canada, Mexico, Greenland, besides many territories and possessions. It encompasses about 9,365,294 square miles (24,256,000 square kilometers), notes the World Atlas website. Plants living in North America include an area stretching between the latitudes of 26 degrees and 85 degrees north, and between longitudes 15 degrees west and 173 degrees east, measuring from sea level to the highest mountains, says Harvard University.
Several North American plants are toxic. For example, the Great Plains region of the United States contains many poisonous plants that can cause severe livestock losses, such as hound's tongue, which causes liver damage and photosensitization. This noxious weed is shaped like a dog's tongue and has stalkless, short stems and dull reddish-purple flowers. It grows in forests, roadsides and meadows. Milkweeds (Solanum species) can cause digestive problems and neurological damage. Other poisonous plants are those such as the leafy fry spurge and noxious knapweeds, notes the University of Lincoln-Nebraska.
The climate of North America has shifted over the long history of the earth, affecting plant life. The striking differences of how the topography of North America has changed can be seen in the biomes map of Ice Age periods. As the earth began to warm, the ice sheet started moving toward the Arctic Circle, causing plants such as pines, spruces and oaks to move northward. Plants of the Ice Age consisted of plants that are unseen today, and left fossils and soil cores proving their past conditions. The North American treeline advanced, moving up mountain slopes to higher elevations.