Flora of North America species comparison

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Juncus acutus

Juncus

sharp rush, spiny rush

jonc, rush
Habit 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.

Juncus acutus

Juncus
Distribution
from FNA
AZ; CA; NV; South America; Mexico (Baja Calif); South Africa; Atlantic Islands
[WildflowerSearch map]
[BONAP county map]
from USDA
Worldwide except Antarctica
[BONAP county map]
Discussion

Subspecies 2 (1 in the flora).

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Species ca. 300 (95 in the flora).

(Discussion copyrighted by Flora of North America; reprinted with permission.)
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
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
subg. Septati
3. Leaves flat, involute or terete, not septate; capsule rarely beaked
subg. Poiophylli
4. Leaves flat or ensiform.
→ 5
4. Leaves terete or compressed.
→ 6
5. Leaves ensiform, imperfectly septate
subg. Ensifolii
5. Leaves flat, not septate
subg. Graminifolii
6. Capsules large; seeds large, long tailed; leaves not noticeably septate
subg. Alpini
6. Capsules smaller; seeds not tailed or if tailed not long; leaves septate or not.
→ 7
7. Leaves not septate; plants halophytic
subg. Juncus
7. Leaves septate; plants usually of fresh water habitats
subg. Septati
Source FNA vol. 22, p. 237. FNA vol. 22. Authors: Ralph E. Brooks*, Steven E. Clemants*.
Parent taxa Juncaceae > Juncus > subg. Juncus Juncaceae
Sibling taxa
J. acuminatus, J. acutiflorus, J. alpinoarticulatus, J. anthelatus, J. arcticus, J. articulatus, J. biglumis, J. bolanderi, J. brachycarpus, J. brachycephalus, J. brachyphyllus, J. brevicaudatus, J. bryoides, J. bufonius, J. bulbosus, J. caesariensis, J. canadensis, J. capillaris, J. capitatus, J. castaneus, J. chlorocephalus, J. compressus, J. confusus, J. cooperi, J. coriaceus, J. covillei, J. debilis, J. dichotomus, J. diffusissimus, J. drummondii, J. dubius, J. dudleyi, J. effusus, J. elliottii, J. ensifolius, J. falcatus, J. filiformis, J. filipendulus, J. georgianus, J. gerardii, J. greenei, J. gymnocarpus, J. hallii, J. hemiendytus, J. howellii, J. inflexus, J. interior, J. kelloggii, J. leiospermus, J. lesueurii, J. longistylis, J. luciensis, J. macrandrus, J. macrophyllus, J. marginatus, J. maritimus, J. megacephalus, J. mertensianus, J. militaris, J. nevadensis, J. nodatus, J. nodosus, J. occidentalis, J. orthophyllus, J. oxymeris, J. parryi, J. patens, J. pelocarpus, J. pervetus, J. phaeocephalus, J. polycephalus, J. regelii, J. repens, J. roemerianus, J. scirpoides, J. secundus, J. squarrosus, J. stygius, J. subcaudatus, J. subtilis, J. supiniformis, J. tenuis, J. texanus, J. textilis, J. tiehmii, J. torreyi, J. trifidus, J. triformis, J. triglumis, J. trigonocarpus, J. uncialis, J. validus, J. vaseyi, J. xiphioides
Subordinate taxa
J. acutus subsp. leopoldii
J. subg. Alpini, J. subg. Ensifolii, J. subg. Genuini, J. subg. Graminifolii, J. subg. Juncus, J. subg. Poiophylli, J. subg. Septati
Name authority Linnaeus: Sp. Pl. 1: 325. (1753) Linnaeus: Sp. Pl. 1: 325. 1753; Gen. Pl. ed. 5; 152, (1754)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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