Grass Family

Roger Spencer, David Aldous and Val Stajsic with assistance from David McGeary

Annual or perennial herbs, often rhizomatous, rarely woody (mostly bamboos). Stems (culms) usually cylindrical, jointed, often hollow in the internodes and solid at the nodes. Leaves 1 per node, sometimes crowded at the base of the stem, alternate and usually in 2 rows, consisting of a sheath, ligule, auricles, collar and blade. Sheath with margins free and overlapping, rarely fused. Ligule at the junction of blade/sheath a hairless or ciliate membrane, a row of hairs, or (rarely) absent. Leaf blade usually linear, occasionally wide, flat, rolled or folded, parallel veined. Flower cluster (inflorescence) with individual flowering units, called spikelets, arranged in open or dense panicles, racemes or spikes (sometimes digitately arranged). Spikelets of 1-many florets borne above 2 (1 or 0) bracts called the upper and lower glumes, the main axis of the spikelet (the rachilla) bearing the florets sometimes extending beyond the terminal floret and occasionally spine tipped. Flowers (florets) mostly bisexual (but one or more florets characteristically sterile in some groups) and with 2-3 fleshy scales (lodicules) thought to be a remnant perianth, within 2 bracts, the lemma (lowermost) and palea (uppermost, occasionally absent). Stamens (0-)3(-6), shortly protruding at flowering. Styles usually 2, plumose. Carpels 2 or 3, united. Fruit a caryopsis.

It is thought that most grasses are derived from bamboo-like ancestors.The savannah grasses arose with the emergence of vast grasslands resistant to fire and grazing and with the evolution of groups having a metabolism suited to warm, dry climates. Most grasses are wind-pollinated with large, versatile anthers that move in the wind and feathery stigmas to catch pollen. Seed dispersal by animals or wind is often aided by the presence of awns.

The grasses are well represented in horticulture (as ornamentals, on playing fields, golf courses and lawns), in agriculture, and as wayside weeds. Only the more commonly cultivated species and cultivars are covered in this account.

Extreme caution is always needed when using grasses in gardens as many propagate rapidly by seed to become widespread environmental weeds. Well known examples include: Pennisetum alopecuroides, Fountain Grass (a disputedly native grass); Pennisetum setaceum, Fountain Grass; Arundo donax, Giant Reed; Cortaderia selloana, Pampas Grass and C. jubata, Purple Pampas. In recent times, Nassella tenuissima, a close relative of the highly aggressive invasive weed N. trichotoma, Serrated Tussock, has been offered for sale but should be eradicated if encountered as it has similar devastating potential.

Lesser known grasses sometimes available in horticulture for amenity, minimum maintenance or revegetation, and occasionally erosion control include: Bothriochloa macra, Red-leg Grass; Briza spp., Quaking Grasses, have attractive pendulous flower heads; Chloris truncata,Windmill Grass; Dichanthium sericeum, Silky Blue Grass; Digitaria didactyla, Queensland Blue Couch Grass; Distichlis distichophylla, Australian Salt Grass; Echinochloa spp., Barnyard Grass; Enneapogon spp.; Eragrostis cilianensis, Stink Grass; Eulalia spp.; Leptochloa sp.; Lophopyrum ponticum; Microlaena stipoides,Weeping Grass; Puccinella distans, Alkali Grass; and Sporobolus virginicus, Prickly Couch. Zoysia macrantha, Marine Couch, is promoted for use on salt-affected land; Spinifex sericeus is a native rhizomatous grass used for binding coastal sand dunes, as is the less desirable, invasive exotic Ammophila arenaria.

Turf grasses: Turf grasses may be divided into two groups according to their major period of growth: cool season grasses and warm season grasses.

Cool season grasses include: Poa pratensis, Kentucky Bluegrass; P. trivialis, Rough Bluegrass; P. annua, Winter Grass; Agrostis stolonifera, Creeping Bentgrass, including the cultivars 'Cobra', 'Penncross', 'Penneagle', 'Viper', 'SR1019', 'SR1020' used on bowling greens, golf greens and quality lawns; A. tenuis, Colonial Bentgrass 'Egmont' which is used on golf greens; Festuca rubra, Creeping Red Fescue; F. rubra var. commutata, Chewing's Fescue; F. arundinacea, Tall Fescue; and Lolium perenne, Perennial Ryegrass, including the cultivars 'Ellet', 'Premier II', 'SR4000' and 'Yatsun' which are used mostly for improved pasture.

Warm season grasses include: Cynodon dactylon, Couchgrass, Hybrid Couchgrasses, C. dactylon × C. transvaalensis, including the cultivars 'Santa Ana', 'Tidwarf' and 'Tifway', and the Australian selections 'Boska' (a Victorian selection), 'Legend' (a Victorian selection), 'Plateau' and 'Wintergreen'; Zoysia japonica, Japanese Lawn Grass; Stenotaphrum secundatum, Buffalo Grass or St Augustine Grass (USA); Pennisetum clandestinum, Kikuyu Grass.

Bamboos: Bamboos have pleasing forms and foliage: they may be variously coloured and sometimes variegated. Growers should investigate their invasive potential before using them: they are either clump forming (pachymorph), or have rapidly spreading runners (leptomorph). Less frequently cultivated bamboos (and some available mainly in the tropics) include: Chusquea spp., Dendrocalamus spp., Nastus spp., Otatea spp., Thyrsostachys siamensis, Schizostachyum funghornii, Fargesia dracocephala and F. nitida, Gigantochloa atroviolacea, Indocalamus tesselatus and the form hamadae; Guadua spp. Unfortunately the prolific seed production and sometimes invasive rhizomes make bamboos prime candidates as environmental weeds and some have been declared noxious.

Ornamental grasses: Some ornamental grasses are grown for their plume-like inflorescences, others for their striking and unusual foliage. Amongst those grasses that have decorative flower heads are: Lagurus ovatus, Hare's Tail Grass; Dichelachne crinita, Long Hair Plume Grass; Miscanthus sinensis, Chinese Silver Grass; Themeda triandra, Kangaroo Grass, Austrostipa elegantissima, and species of Pennisetum; still others such as Molinia caerulea, Purple Moor Grass, and Imperata cyclindrica 'Rubra', Japanese Blood Grass, have particularly colourful and ornamental foliage.

Cereal crops, pasture and wayside grasses: Many exotic grasses have been introduced as cereals and pasture grasses and have escaped to become common roadside and wayside plants often colonising waste and disturbed land. Because they are (or were) elements of the cultivated flora the commoner ones have been described in this account. Examples include: Setaria verticillata, Green Bristle Grass; Paspalum dilatatum, Paspalum; Bromus catharticus, Prairie Grass; Ehrharta spp.; Sporobolus africanus; Holcus lanatus, Yorkshire Fog; Hordeum spp.; Vulpia spp.

Grass identification generally requires a hand lens or microscope as it entails inspection of the details of the spikelet structure, also the texture, shape and nerve number of the lemma and glumes, and the presence or absence of awns.

The botanical classification of Poaceae (also known as Gramineae) is in a state of flux but generally 6 subfamilies are recognised (Arundinoideae, Bambusoideae, Centothethecoideae, Chloridoideae , Panicoideae, Pooideae). The subfamilies are divided into about 40 tribes which, in turn, encompass a number of genera. For example, subfamily Pooideae includes the Tribes Stipeae, Poeae, Meliceae, Aveneae, Bromeae and Triticeae; the tribe Poeae includes the genera Festuca, Dryopoa, Puccinellia, Poa and Austrofestuca.

Seed, occasionally division, rarely cuttings (bamboos).

An economically important family. Cereal grains provide more than 50% of the world's food as, in order of quantity produced Triticum, Wheat; Oryza, Rice; Zea, Maize or Corn; Hordeum, Barley; Avena, Oats; Sorghum; Secale, Rye; millets. Rice is the favoured food in the tropics and subtropics while wheat is mostly a temperate crop. Animals that use plants of this family as fodder and forage produce the bulk of consumed meat; pigs and poultry are fed with cereals. Bamboos are used structurally and for a range of other purposes such as musical instruments and paper production (along with several other grasses). Sugar cane is commercially important and aromatic oils are extracted from some species such as Cymbopogon, Lemon Grass, and Vetiveria (vetiver oil). Alcoholic beverages are made from Oryza (sake), Saccharum (rum), Hordeum, Secale, Triticum and Zea (beer and whiskeys). Turf grasses are widely used in sports fields, arenas and golf courses.

It is important to distinguish between the families Poaceae (grasses), Cyperaceae (sedges), and Juncaceae (rushes), all of which may have grass-like leaves. The sedges, Cyperaceae, have stems that are generally 3-angled and solid with 3-ranked leaves (not 2-ranked as in Poaceae), the leaf sheaths are closed (mostly open in Poaceae); the florets are subtended by a single bract (not 2 as in Poaceae), the fruit is an achene (nutlet) not caryopsis (as in Poaceae). The rushes, Juncaceae, have a 1-3 chambered capsular fruit containing 3-many seeds and generally 6 perianth segments radially arranged (Poaceae has insignificant, asymmetrically arranged perianth segments (lodicules), which are hidden by the lemma and palea).

668-785 genera and about 9500 species (about a third of the species are in 10 genera: Agrostis, Aristida, Calamagrostis, Digitaria, Eragrostis, Festuca, Panicum, Paspalum, Poa, Stipa). Cosmopolitan: mostly tropical and northern temperate sub-arid regions, but well represented in Australia, South America and South Africa.

Hubbard (1984), Lambrechtsen (1986), Lamp et al. (1990), Watson & Dallwitz (1992), Flora of Australia Volumes 43, 44 (2002- ). Turf: Beard (1973), Aldous (1999), Aldous and Chivers (2002); Sharp, D. & Simon, B.K. (2002) (this is a CD for grass identification in Australia). On the web biodiversity.uno.edu/delta/grass/ is a source of useful information.

Source: Spencer, R.; Aldous, D.; Stajsic, V.; McGeary, D (2005). Poaceae. In: Spencer, R.. Horticultural Flora of South-eastern Australia. Volume 5. Flowering plants. Monocotyledons. The identification of garden and cultivated plants. University of New South Wales Press.

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kingdom Plantae
phylum   Tracheophyta
class    Magnoliopsida
superorder     Lilianae
order      Poales
Higher taxa
Subordinate taxa
genus        Agrostis Desf.
genus        Alopecurus L.
genus        Ammophila Host.
genus        Anthosachne
genus        Anthoxanthum L.
genus        Arrhenatherum P.Beauv.
genus        Arundinaria Michx.
genus        Arundo L.
genus        Austrodanthonia H.P. Linder
genus        Avena L.
genus        Bambusa Schreb.
genus        Bromus L.
genus        Calamagrostis Adans.
genus        Chimonobambusa Mak.
genus        Chloris O. Swartz
genus        Coix L.
genus        Cortaderia Stapf
genus        Cymbopogon Spreng.
genus        Cynodon Rich.
genus        Cynosurus L.
genus        Dactylis L.
genus        Dichanthium Willemet.
genus        Dichelachne Endl.
genus        Digitaria Haller.
genus        Elymus L.
genus        Festuca L.
genus        Glyceria R.Br.
genus        Holcus L.
genus        Hordeum L.
genus        Imperata Cyr.
genus        Lagurus L.
genus        Lolium L.
genus        Microlaena R.Br.
genus        Milium L.
genus        Miscanthus Anderss.
genus        Molinia Schrank
genus        Oryza L.
genus        Panicum L.
genus        Paspalum L.
genus        Pennisetum Rich.
genus        Phalaris L.
genus        Phragmites Adans.
genus        Phyllostachys Sieb. & Zucc.
genus        Pleioblastus Nakai
genus        Poa L.
genus        Pseudosasa Nakai
genus        Rytidosperma
genus        Saccharum L.
genus        Sasa Mak. & Shib.
genus        Secale L.
genus        Semiarundinaria Nakai
genus        Setaria P.Beauv.
genus        Shibataea Makino ex Nakai
genus        Sorghum Moench
genus        Stenotaphrum Trin.
genus        Stipa L.
genus        Themeda Forssk.
genus        Triticum L.
genus        Zea L.
genus        Zoysia Willd.