| # The grass genera of the world |

L. Watson, T.D. Macfarlane, and M.J. Dallwitz

### Phragmites Adans.

From the Greek phragma, alluding to its fence-like bordering of waterways.

Type species: Type: P. australis (Cav.) Trin. ex Steud.

Including Czernya Presl, Miphragtes Nieuwland, Oxyanthe Steud., Trichoon Roth, Xenochloa Roem. & Schult.

Habit, vegetative morphology. Perennial; reedy (often forming dense stands); rhizomatous and stoloniferous. Culms 60–400 cm high (-1000 cm); woody and persistent to herbaceous (often somewhat persistent); branched above (especially when main culm damaged), or unbranched above. Culm nodes glabrous. Culm internodes hollow. Young shoots extravaginal. Leaves not basally aggregated; auriculate (scarcely), or non-auriculate. Leaf blades linear-lanceolate to lanceolate; broad; 6–50 mm wide; flat, or rolled (convolute); not pseudopetiolate; without cross venation; disarticulating from the sheaths; rolled in bud. Ligule a fringe of hairs. Contra-ligule absent.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.

Inflorescence. Inflorescence paniculate; open (20–60 cm long, plumose, the fertile lemmas surrounded by long white silky hairs); with capillary branchlets (towards the spikelets); espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.

Female-fertile spikelets. Spikelets 9–16 mm long; compressed laterally; disarticulating above the glumes (at least above the L1); disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; hairy (with very long white hairs, but only above the disarticulation zones of the florets); the rachilla extension with incomplete florets. Hairy callus present (with long fine silky hairs). Callus long (and slender); blunt.

Glumes two; very unequal; shorter than the spikelets; shorter than the adjacent lemmas; pointed; awnless; non-carinate (rounded on the back); similar (membranous). Lower glume 3–5 nerved. Upper glume 3–5 nerved. Spikelets with incomplete florets. The incomplete florets both distal and proximal to the female-fertile florets. The distal incomplete florets merely underdeveloped. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; paleate; male (the stamens often 2), or sterile. The proximal lemmas awnless; 3(–7) nerved; more or less equalling the female-fertile lemmas; similar in texture to the female-fertile lemmas (membranous); not becoming indurated.

Female-fertile florets (2–)3–10. Lemmas narrow, lanceolate; similar in texture to the glumes (membranous); not becoming indurated; entire; pointed (acute to acuminate or aristulate); awnless, or awned (narrow-attenuate, muticous to aristulate). Awns (if lemmas aristulate) 1; median; apical; non-geniculate; much shorter than the body of the lemma. Lemmas hairless; glabrous; non-carinate; without a germination flap; 1–3 nerved. Palea present; conspicuous but relatively short; entire; awnless, without apical setae (glabrous); 2-nerved. Lodicules present; 2; free; fleshy; ciliate, or glabrous. Stamens 3. Anthers 0.6–2.5 mm long; not penicillate. Ovary apically glabrous. Styles fused. Stigmas 2; brown.

Fruit, embryo and seedling. Fruit free from both lemma and palea; small; compressed dorsiventrally (to sub-terete). Hilum short. Embryo large; not waisted. Endosperm hard; without lipid; containing compound starch grains. Embryo without an epiblast; with a scutellar tail; with an elongated mesocotyl internode. Embryonic leaf margins meeting.

Seedling with a short mesocotyl, or with a long mesocotyl. First seedling leaf with a well-developed lamina. The lamina broad; curved; 13–20 veined.

Ovule, embryology. Outer integument extensive, being absent only from the micropylar region. Inner integument continuous, the micropyle constricted. Synergids not haustorial.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally (fairly thick walled). Intercostal zones with typical long-cells, or exhibiting many atypical long-cells (with many of them short). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present, or absent; when present, panicoid-type; 24–28.5 microns long; 4.5–6.3 microns wide at the septum. Microhair total length/width at septum 4.5–5.3. Microhair apical cells 12–13.5 microns long. Microhair apical cell/total length ratio 0.47–0.5. Stomata common; (30–)33–34.5(–36) microns long. Subsidiaries low dome-shaped. Guard-cells overlapped by the interstomatals, or overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs; silicified. Intercostal silica bodies rounded, or crescentic. Costal short-cells neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies rounded, or horizontally-elongated smooth to tall-and-narrow (or cuboid), or crescentic; not sharp-pointed.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade; with arm cells. Leaf blade adaxially flat. Midrib conspicuous; having a conventional arc of bundles. Bulliforms present in discrete, regular adaxial groups; in simple fans (these with deeply penetrating median cells), or associated with colourless mesophyll cells to form deeply-penetrating fans (a few), or combining with colourless mesophyll cells to form narrow groups penetrating into the mesophyll. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; nowhere forming ‘figures’. Sclerenchyma all associated with vascular bundles.

Culm anatomy. Culm internode bundles in one or two rings, or in three or more rings.

Phytochemistry. Tissues of the culm bases with abundant starch. Leaves without flavonoid sulphates (2 species).

Special diagnostic feature. Female-fertile lemmas hairless; ligule hairs longer than 0.5 mm, longer than the membrane.

Cytology. Chromosome base number, x = 12. 2n = 36, 44, 46, 48, 49, 50, 51, 52, 54, and 96. 3, 4, and 8 ploid (and aneuploids). Chromosomes ‘small’.

Classification. Watson & Dallwitz (1994): Arundinoideae; Arundineae. Soreng et al. (2015): Arundinoideae; Molinieae. 3 species.

Distribution, phytogeography, ecology. Cosmopolitan.

Helophytic.

Economic aspects. Significant weed species: P. australis, P. karka (causing water loss and stagnation, and impeding navigation. Used for mats and thatching.

Rusts and smuts. Rusts — Puccinia. Smuts from Tilletiaceae and from Ustilaginaceae. Tilletiaceae — Neovossia. Ustilaginaceae — Ustilago.

References, etc. Leaf anatomical: Metcalfe 1960; studied by us - P. australis (Cav.) Trin. ex Steud.

Illustrations. • Phragmites australis (as P. communis), general aspect: Eng. Bot. (1872). • General aspect (P. australis): Gibbs Russell et al., 1990. • Ligule of Phragmites australis. • Spikelet close-up of Phragmites australis: this project. Phragmites australis. Rachilla with long, white, silky hairs. • Phragmites australis, abaxial epidermis of leaf blade: this project. • Phragmites australis: abaxial epidermis of leaf blade showing a microhair: this project. A rare microhair. • Phragmites australis, T.S. of leaf blade - fluorescence image: this project. • Phragmites australis, TS section of leaf blade: this project. • Phragmites australis, TS section of leaf blade with arm-cells: this project. Phragmites australis. Mesophyll of arm cells. • Phragmites australis, mesophyll of arm-cells: this project. Phragmites australis. Mesophyll of arm cells. • Phragmites karka: Gardner, 1952. • Phragmites mauritianus: Kunth (1835). • Grass pollen antigens: Watson and Knox (1976).

We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, and classifications. See also Guidelines for using data taken from Web publications.

Cite this publication as: ‘Watson, L., Macfarlane, T.D., and Dallwitz, M.J. 1992 onwards. The grass genera of the world: descriptions, illustrations, identification, and information retrieval; including synonyms, morphology, anatomy, physiology, phytochemistry, cytology, classification, pathogens, world and local distribution, and references. Version: 15th June 2025. delta-intkey.com’.

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