Families of Vascular Plants - Botany 307F 

Poales - Poaceae ("Gramineae")

715 genera/10,550 spp. worldwide, especially in tropical and north temperate, sub-arid habitats; perennial, often rhizomatous herbs or tree-like (but with primary growth only - bamboos).

Flowers usually bisexual, wind-pollinated, in 1- to many-flowered spikelets, these in turn arranged in spikes or panicles.  Fruit a caryopsis, the coat of the single seed within joined to the ovary wall.  C4 photosynthesis has apparently evolved repeatedly within the family, enhancing the efficiency of photosynthesis under conditions of high temperatures and limited water availability.  Leaf growth from basal, intercalary meristems, together with the clumped or rhizomatous habit, enable grasses to tolerate burning and grazing. Grasslands (prairies, steppes, savannas) are some of the most productive ecosystems in the world, sometimes even after conversion to grain production. Even in Ontario, prairie vegetation can be found where local conditions have permitted it to persist, and where agricultural activity or urbanization have not yet destroyed it.

Culms (stems) of Saccharum (Andropogoneae) a major source of sucrose globally; cane sugar.  Culms of bamboos (Bambuseae) a source of building materials in many (sub-) tropical societies.  Cultivation for their endosperm of genera in these same two tribes (millet, maize; rice), as well as in the Triticeae (barley, rye, wheat) and Aveneae (oats), has made whole civilizations possible.

Because of their importance in the human economy as well as their biological significance, the Poaceae have been the focus of considerable research into their phylogeny. For a 2002 update on grass phylogeny by an expert on the family click HERE. For the most up to date results use the APW link below and click on Poales.

POACEAE (classification as in Mabberley 2008 ; compare Zomlefer 1994, pp. 350-356);

subfamilies, tribes, and exemplar genera; Ontario genera with asterisks).

I. Bambusoideae, including:

Bambuseae (bamboos)

II. Ehrhartioideae, including:

Rice (Oryza), and (in North America) "wild" or (in Manchuria) "water" rice (Zizania)

III. Pooideae, including:


IV. Centothecoideae (broad-leaved mainly rain forest herbs)

V. Arundinoideae, including:


VI. Chloridoideae (C4 photosynthesis, leaf anatomy; adapted to high light intensity; spikelets shattering at maturity), including:


VII. Panicoideae (usually with C4 photosynthesis, leaf anatomy; spikelets 2-flowered, the lower male or sterile), including:


Flora North AmericaThe Flora North America treatment of the Poaceae (Vol. 24-25) is available online as the...

Manual of Grasses for North America


The Families of Flowering Plants 
DELTA database in natural language

L. Watson and M. J. Dallwitz

see also their

Grass Genera of the World


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GrassBase - The Online World Grass Flora

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Please send your comments to tim.dickinson@utoronto.ca; last updated 17-Apr-2011