Amphipogon turbinatus, copyright Gerald Krygsman.

Belongs within: Poaceae.

The Arundinoideae, reeds, are a group of mostly perennial grasses that often possess hollow culms (Grass Phylogeny Working Group 2001).

From giant reeds to tiny leaves
Published 3 July 2012
Giant reed Arundo donax, photographed by Russ Kleinman & Richard Felger.

The grasses are without a doubt one of the most successful groups of plants in the modern environment. So it is only fitting that for today’s post I’m going to be looking at one of the subgroups of the grasses, the Arundinoideae.

The Arundinoideae, including the reeds and related species, has been long recognised as a subfamily of grasses, but rather vaguely so. Most of the characters of leaf anatomy previously used to define the group are either plesiomorphies or absences. Arundinoids use the plesiomorphic C3 photosynthetic pathway rather than the derived C4 pathway and lack the radiate leaf anatomy associated with C4 photosynthesis. They also lack the fusoid leaf cells with accessory arm cells that are characteristic of the bamboos. In other features, ‘arundinoids’ were quite variable, and it therefore came as no surprise to anyone when phylogenetic analyses indicated that the group was polyphyletic. As a result, the Grass Phylogeny Working Group (2001) divided the arundinoids between a number of subfamilies, separating the wiregrasses as the Aristidoideae and the oatgrasses and pampas grasses as the Danthonioideae. This reduced the Arundinoideae proper, previously including well over 600 species, to less than 40.

Common reed Phragmites australis, from here.

Even so, the arundinoids remain a disparate group, and morphological synapomorphies of the group remain elusive. The taxonomic core of the group, the reeds of the genera Arundo, Phragmites and Molinia, are connected by the possession of hollow culm internodes, a punctiform hilum (the detachment scar on the ‘seed’) and convex adaxial rib sides in the leaf blade (Grass Phylogeny Working Group 2001), but these features are not shared by all other arundinoids. The reeds are found in damp habitats, and the common reed Phragmites australis can grow in standing water. The largest species, the giant reed Arundo donax, can reach a height of ten metres under ideal growth conditions. In contrast, the Tom Thumb grass Dregeochloa pumila is found in the Namib Desert of South Africa and Namibia, and doesn’t reach any higher than 25 mm (excluding the flower stalk, which may give it another inch or so). Dregechloa pumila is also remarkable as the only succulent species of grass. Also included in the Arundinoideae are the crinipoid grasses, a somewhat poorly known assemblage of species found in highlands of Africa, Madagascar and southern India (Linder et al. 1997).

Tom Thumb grass Dregechloa pumila, from Ernst van Jaarsveld.

Arundo donax has become known in some areas as an agressive weed, particularly in the US. It has one of the fastest growth rates of any plant, potentially up to ten centimetres in a single day (remember, that’s four Dregeochloas!) Despite its invasive potential, some have been promoting it as a potential crop species, particularly for the biofuel market (presenting its fast growth rate as an outright advantage). Arundo donax is also the preferred material for woodwind reeds. Phragmites australis (also a problematic weed in the wrong circumstances) has been used in wastewater purification, and Wikipedia also notes that it is edible, quoting that the young stems “while still green and fleshy, can be dried and pounded into a fine powder, which when moistened is roasted like marshmallows”. ‘Like’ marshmallows, perhaps, but I don’t think that I’ll be rushing to make the substitution.

Systematics of Arundinoideae

Characters (from Grass Phylogeny Working Group 2001): Plants perennial (rarely annual), rhizomatous, stoloniferous, or caespitose, herbaceous to somewhat woody. Culms hollow or less commonly solid. Leaves distichous; abaxial ligule absent or rarely present as a line of hairs; adaxial ligule a fringed or unfringed membrane or a fringe of hairs; blades relatively broad to narrow, without pseudopetioles, venation parallel; sheaths usually non-auriculate. Inflorescences usually paniculate, rarely spicate or racemose, bracts outside of spikelets absent. Spikelets with bisexual florets, glumes 2, a sterile lemma sometimes present, female-fertile florets 1 to several, apical reduction usually present, usually laterally compressed, disarticulating above glumes; lemma lacking uncinate macrohairs, if awned, awn usually single, sometimes awns three, but then lacking a basal column; palea usually well developed; lodicules 2, free (rarely joined at the base), fleshy, glabrous or infrequently ciliate, not or scarcely vascularized to heavily vascularized; stamens (1 to) 3; ovary glabrous, apical appendage absent, haustorial synergids absent, styles 2, usually free, close, stigmas 2. Caryopsis with hilum short or long-linear; endosperm hard, without lipid, containing compound starch grains; embryo large or small, epiblast absent, scutellar cleft present, mesocotyl internode elongated, embryonic leaf margins meeting or overlapping. Basic chromosome numbers x = 6, 9, 12. Mesophyll nonradiate or rarely radiate, without an adaxial palisade layer, without fusoid cells, arm cells absent or present; Kranz anatomy absent; midrib simple; adaxial bulliform cells present. Stomata with low dome-shaped or triangular subsidiary cells; bicellular microhairs present or less commonly absent, when present usually of panicoid-type; papillae usually absent.
Photosynthetic pathway C3.

<==Arundinoideae [Arundineae, Phragmitoideae]
    |--+--Molinia caeruleaGPWG01
    |  `--PhragmitesGPWG01
    |       |--P. australis (Cav.) Trin ex Steud. 1820BF89 (see below for synonymy)
    |       |--P. karka (Retz.) Trin ex Steud. 1841 [=Arundo karka]G52
    |       |--P. vallatoriaVB02
    |       `--P. vulgarisPB27
       |    |--A. conspicua (see below for synonymy)C06
       |    |--A. donaxGPWG01
       |    |    |--A. d. var. donaxG52
       |    |    `--A. d. var. versicolorG52
       |    |--A. fulvida Buch. 1874 [=A. conspicua var. fulvida]C06
       |    `--A. groenlandicaGT02
       `--AmphipogonGPWG01 [incl. GamelythrumB78]
            |--A. amphipogonoides (Steud.) Vickery 1950 [=Pentacraspedon amphipogonoides; incl. A. confusus]G52
            |--A. caricinusGPWG01
            |--A. carinatusMLP09
            |--A. debilis Br. 1819 [=Aegopogon debilis; incl. Am. brownii]G52
            |    |--A. d. var. debilisG52
            |    `--A. d. var. fallaxG52
            |--A. laguroides Br. 1810G52 [=Aegopogon laguroidesB78; incl. Am. cygnorumG52]
            |--A. strictus Br. 1810G52 [=Aegopogon strictusB78; incl. Am. caricinusB78]
            |    |--A. s. var. strictusB78
            |    |--A. s. var. avenaceusB78
            |    |--A. s. var. desertorumG52
            |    |--A. s. var. gracilisB78
            |    `--A. s. var. setiferB78
            `--A. turbinatus Br. 1810 (see below for synonymy)G52
Arundinoideae incertae sedis:
  Dregeochloa Conert 1966EN20
    `--*D. pumila (Nees) Conert 1966 [=Danthonia pumila Nees 1899]EN20
  Moliniopsis japonicaGPWG01
  Elytrophorus spicatus (Willd.) Camus 1923GPWG01, G52 (see below for synonymy)
  Zenkeria elegansGPWG01, S03

Amphipogon turbinatus Br. 1810 [=Aegopogon turbinatus, Gamelythrum turbinatum; incl. G. denudatum, Amphipogon restionaceus]G52

Arundo conspicua [=Achnatherum conspicuum, Agrostis conspicua, Calamagrostis conspicua; incl. Arundo australis, Ar. kakao, Gynerium zeelandicum]C06

Elytrophorus spicatus (Willd.) Camus 1923GPWG01, G52 [=Dactylis spicataG52, Sesleria spicataG52; incl. Elytrophorus articulatusG52]

Phragmites australis (Cav.) Trin ex Steud. 1820BF89 [incl. P. communis (Lin.) Trin. 1820H93, S06, Amphigala congesta Lowe 1838S06, Arundo isiacaeBG96, Phragmites communis var. isiacaBG96, Ar. phragmites Lin. 1753S06, P. phragmitesS06]

*Type species of generic name indicated


[BG96] Baka, Z. A., & H. B. Gjaerum. 1996. Egyptian Uredinales. 1. Rusts on wild plants from the Nile Delta. Mycotaxon 60: 291–303.

[B78] Bentham, G. 1878. Flora Australiensis: A description of the plants of the Australian Territory vol. 7. Roxburghiaceae to Filices. L. Reeve & Co.: London.

[BF89] Burnham, B. H., & P. E. Fell. 1989. Distribution of Melampus bidentatus (Say) and Succinea wilsoni (Lea) within a tidal marsh in eastern Connecticut. Nautilus 103 (3): 109–112.

[C06] Cheeseman, T. F. 1906. Manual of the New Zealand Flora. John Mackay, Government Printer: Wellington.

[EN20] Eggli, U., & R. Nyffeler (eds) 2020. Illustrated Handbook of Succulent Plants: Monocotyledons 2nd ed. Springer.

[G52] Gardner, C. A. 1952. Flora of Western Australia vol. 1 pt 1. Gramineae. William H. Wyatt: Perth.

[GT02] Gomez, B., F. Thévenard, M. Fantin & L. Guisberti. 2002. Late Cretaceous plants from the Bonarelli Level of the Venetian Alps, northeastern Italy. Cretaceous Research 23: 671–685.

[GPWG01] Grass Phylogeny Working Group. 2001. Phylogeny and subfamilial classification of the grasses (Poaceae). Annals of the Missouri Botanical Garden 88 (3): 373–457.

[H93] Hickman, J. C. (ed.) 1993. The Jepson Manual: Higher Plants of California. University of California Press: Berkeley (California).

Linder, H. P., G. A. Verboom & N. P. Barker. 1997. Phylogeny and evolution in the Crinipes group of grasses (Arundinoideae: Poaceae). Kew Bulletin 52 (1): 91–110.

[MLP09] McKenzie, N. L., S. van Leeuwen & A. M. Pinder. 2009. Introduction to the Pilbara Biodiversity Survey, 2002–2007. Records of the Western Australian Museum Supplement 78 (1): 3–89.

[PB27] Pilsbry, H. A., & J. Bequaert. 1927. The aquatic mollusks of the Belgian Congo, with a geographical and ecological account of Congo malacology. Bulletin of the American Museum of Natural History 53 (2): 69–602, pls 10–77.

[S03] Singh, J. N. 2003. Grasses and their hydro-edaphic characteristics in the grassland habitat of Nilgiris Biosphere Reserve, Tamil Nadu. Bulletin of the Botanical Survey of India 45: 143–164.

[S06] Stuckert, T. 1906. Segunda contribución al conocimiento de las gramináceas Argentinas. Anales del Museo Nacional de Buenos Aires, serie 3, 6: 409–555.

[VB02] Vijay, S. K., & T. N. Bhardwaja. 2002. Vegetation and phenodynamics of wetlands of central Rajasthan. Journal of the Bombay Natural History Society 99 (3): 573–581.

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