Description: Rhizomatous perennials. Culms terete, often rather bulbously thickened at base.
Leaves reduced to sheaths along, and at the base of, the culm.
Inflorescence as long as or longer than culms, occasionally functionally unisexual (on the same plant), with numerous 1-grooved to flattened branches, the ultimate spikelet-bearing branchlets elongating with maturity. Spikelets with 1 bisexual or female flower, often with a male below it. Glumes 3–6, spirally arranged, usually puberulous on adaxial surface near apex, lower glumes empty, uppermost occasionally reduced or empty. Perianth absent. Stamens 3–6. Style 3–5-fid; style base narrow-conical to pyramidal, thick, hispid at apex, smooth and shining below, persistent on nut.
Nut trigonous to terete, readily deciduous, glabrous, with a narrow elongated neck between body of nut and style base.
Distribution and occurrence: World: c. 7 species, endemic Australia. Australia: all States except N.T.
Note: nut length includes the narrow neck below the style base as well as the broader body. The distribution of male and female flowers and spikelets varies greatly. What appear to be functionally male and female inflorescences can occur on culms side by side on the same rhizome. The life cycle of these plants needs study.
Text by K. L. Wilson
Taxon concept:
| | Key to the species | |
| 1 | Ultimate branches of inflorescence strongly curled to flexuous, at least in female inflorescences | 2 |
| Ultimate branches of inflorescence straight, erect or drooping | 3 |
| 2 | Stamens 3 or 4; ultimate branches similarly curly in all inflorescences; few sterile ultimate branches present | Caustis flexuosa |
| Stamens 5 or 6; ultimate branches of 'female' inflorescence more curly than in 'male'; numerous sterile ultimate branches present in 'female' inflorescences
Back to 1 | Caustis recurvata |
| 3 | Style 3-fid; numerous sterile ultimate branches in inflorescence, giving a rather dense, erect, finely leafy appearance; stamens 3 or 4; leaf sheaths not wrinkled; glumes 5–7.5 mm long | Caustis blakei |
| Style 4- or 5-fid; few sterile ultimate branches in inflorescence, giving an open, drooping, wiry appearance; stamens 5; leaf sheaths wrinkled near apex with maturity; glumes 9–13 mm long
Back to 1 | Caustis pentandra |
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