Herbs, perennial, rhizomatous rhizomatous, orsometimes cespitose. Culms flattened, 2-edged, smooth. Leaves basal and cauline; blade ensiform (flattened with 1 edge facing culm), imperfectly septate. Inflorescences terminal panicles of 2–many heads, sympodial; bracteoles absent proximal to perianth. Flowers in multiflowered heads. Capsules 1-locular, apex separating at dehiscence. Seeds not tailed or occasionally tailed, tegmen reticulate and usually lined. 2n = 20.

Distribution

w North America, Mexico, e Asia (s to Japan).

Discussion

Juncus subg. Ensifolii may be polyphyletic. Juncus polycephalus shows affinities with J. scirpoides, J. megacephalus, and J. validus; the remaining members show affinities with J. nevadensis, J. megacephalus, and J. dubius.

Species ca. 7 (6 in the flora).

Selected References

None.

Lower Taxa

Juncus ensifolius, Juncus macrandrus, Juncus oxymeris, Juncus phaeocephalus, Juncus polycephalus, Juncus xiphioides

Key

1	Capsules cylindric to ovoid, acute to obtuse proximal to beak, 2.7–3.8 mm (including beak): style usually less than 1 mm.	> 2
1	Capsules lanceolate to subulate, tapering to beak, 3.3–5.6 mm (including beak); style usually more than 1 mm.	> 3
2	Plants robust, usually more than 6 dm; leaves 7–12 mm wide (rarely to 3 mm wide): capsules acuminate, without beak; stamens 6	Juncus xiphioides
2	Plants not robust, 2–5 dm; leaves 1.5–6 mm wide; capsules obtuse proximal to beak; stamens 3 or 6	Juncus ensifolius
3	Body of capsule included, beak may be slightly exserted.	> 4
3	Body of capsule exserted.	> 5
4	Capsules rounded proximal to beak; tepals 3–4 mm; inflorescences with 10 or more 6–12-flowered heads	Juncus macrandrus
4	Capsules acute proximal to beak; tepals 3.3–4.8 mm; inflorescences variable	Juncus phaeocephalus
5	Heads spheric, 20–30-flowered; capsules narrowly lanceolate, apex remaining united after dehiscence	Juncus polycephalus
5	Heads hemispheric or narrower, 3–11-flowered; capsules broadly lanceolate, apex usually separating at dehiscence	Juncus oxymeris