Grasses

Hundreds of species of grasses are native to North America. Native grasses are present in virtually all habitats, and they are among the most dominant plants in prairies, some types of marshes, and similar, herbaceous types of vegetation. In addition, many species of grasses have been introduced by humans from elsewhere, especially from western Eurasia.

Although many rich varieties of form and function are represented by the native grasses of North America, only a few of the most prominent species of selected, grass-dominated habitats will be briefly mentioned.

The temperate prairies of North America are dominated by herbaceous perennial plants, many of which are species of grasses. In the tall-grass prairies, some of the grasses can grow as high as 6.5 ft (2 m). Examples of these tall species include the big blue-stem (Andropogon gerardi), indian grass (Sorghastrum nutans), dropseed (Sporobolus asper), needle grass (Stipa spartea), panic grass (Panicum virgatum), wild rye (Elymus virginicus), and others. Somewhat drier sites support mixed-grass prairies containing shorter species, for example, little blue-stem (Andropogon scoparius), grama grass (Bouteloua gracilis), wheat grass (Agropyron smithii), and green needlegrass (Stipa viridula). The driest habitats support semi-arid, short-grass prairies with species such as grama grasses (Bouteloua dactyloides and B. gracilis), dropseed (Sporobolus cryptandrus), muhly grass (Muhlenbergia torreyana), and Junegrass (Koerlia comata).

Some species of grasses can be abundant in marshes, including the reed (Phragmites communis) which can reach a height greater than 13 ft (4 m) and is North America's tallest grass. The reed is a very widespread species, occurring in marshes on all of the continents. Some seaside habitats can also develop perennial grasslands. Sandy habitats are typically dominated by species of grasses such as the beach grass (Ammophila breviligulata), sand-reed (Calamovilfa longifolia), and beach rye (Elymus mollis). Salt-marshes are brackish, estuarine habitats that are typically dominated by cord grasses, such as Spartina alterniflora and S. patens, two species which segregate within the same salt-marshes on the basis of salinity and moisture gradients.

Although it was actually introduced to North America from Europe, the so-called Kentucky blue-grass (Poa pratensis) is now a very widespread species. Kentucky blue-grass is one of the most common species in lawns, and it also occurs widely in disturbed habitats.