Sp. Pl. 1: 325. 1753; Gen. Pl. ed. 5; 152, 1754.

Common names: Rush jonc
Etymology: classical name for the genus
Treatment appears in FNA Volume 22.

Herbs, perennial or rarely annual, rhizomatous or cespitose. Culms round or flattened in cross section. Cataphylls often present at culm base. Leaves: sheaths open; blade flat, channeled, ensiform or terete, sometimes septate, margins involute. Inflorescences terminal or pseudoaxillary, monochasia or dichasia, usually with monochasial branches, cymes or 1–many heads in racemes or panicles; bracteoles 2 or absent. Flowers: tepals (4–)6 in 2 whorls; stamens (2–)3–6. Capsules 1-locular or 3-locular, septicidal. Seeds many, ellipsoid to ovoid, sometimes tailed.


Worldwide except Antarctica.


Species ca. 300 (95 in the flora).


1 Flowers borne singly; bracteoles present (except J. pelocarpus, J. subtilis). > 2
1 Flowers in heads; bracteoles absent. > 4
2 Inflorescences appearing lateral, inflorescence bract terete, erect, appearing to be continuation of culm; basal leaves bladeless, cauline leaves absent Juncus subg. Genuini
2 Inflorescences appearing terminal, inflorescence bract erect or ascending, flat, involute or terete; basal leaves (at least some) usually with blade, cauline leaves present or absent. > 3
3 Leaves terete, septate; capsules beaked Juncus subg. Septati
3 Leaves flat, involute or terete, not septate; capsule rarely beaked Juncus subg. Poiophylli
4 Leaves flat or ensiform. > 5
4 Leaves terete or compressed. > 6
5 Leaves ensiform, imperfectly septate Juncus subg. Ensifolii
5 Leaves flat, not septate Juncus subg. Graminifolii
6 Capsules large; seeds large, long tailed; leaves not noticeably septate Juncus subg. Alpini
6 Capsules smaller; seeds not tailed or if tailed not long; leaves septate or not. > 7
7 Leaves not septate; plants halophytic Juncus subg. Juncus
7 Leaves septate; plants usually of fresh water habitats Juncus subg. Septati