Juncus

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.

Distribution

Worldwide except Antarctica.

Discussion

Species ca. 300 (95 in the flora).

Selected References

Engelmann, G. 1866--1868. Revision of the North American species of the genus Juncus, with a description of new or imperfectly known species. Trans. Acad. Sci. St. Louis. 2(2, 3): 424--498.

Hermann, F. J. 1975. Manual of the Rushes (Juncus spp.) of the Rocky Mountains and Colorado Basin. Fort Collins, Colo. [U.S.D.A. Forest Serv. , Gen. Techn. Rep. RM-18.] *SEC authored Juncus Linnaeus subg. Ensifolia and subg. Septati. All other subgenera were written by REB.

Lower Taxa

Juncus subg. Alpini, Juncus subg. Ensifolii, Juncus subg. Genuini, Juncus subg. Graminifolii, Juncus subg. Juncus, Juncus subg. Poiophylli, Juncus subg. Septati

Key

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