Flora of North America species comparison

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Juncus polycephalus

Juncus

flatleaf rush, manyhead rush

jonc, rush
Habit Herbs, perennial, cespitose, 6–10 dm. Herbs, perennial or rarely annual, rhizomatous or cespitose.
Culms

erect, 3–14 mm diam.

round or flattened in cross section.
Cataphylls

absent.

often present at culm base.
Leaves

basal 2–3(–6), cauline 1–4, brownish green;

auricles absent;

blade 8–70 cm × 4–8 mm.

sheaths open;

blade flat, channeled, ensiform or terete, sometimes septate, margins involute.
Inflorescences

panicles of 16–82 heads, 10–30 cm;

primary bract erect;

heads 20–30-flowered, spheric, 8–12 mm diam.

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 green to reddish, lance-subulate, 3–4 mm, nearly equal, apex acuminate;

stamens 3, anthers 1/3–1/2 length of filaments.

tepals (4–)6 in 2 whorls;

stamens (2–)3–6.
Capsules

exserted, straw-colored, 1-locular, narrowly ovoid, 4–5 mm, apex tapering to beak, remaining after dehiscence.

1-locular or 3-locular, septicidal.
Seeds

lance-ellipsoid, 0.5–0.6 mm, not tailed.

many, ellipsoid to ovoid, sometimes tailed.

Juncus polycephalus

Juncus
Phenology Fruiting spring–fall.
Habitat Wet or seasonally wet shores, depressions, occasionally in fairly deep water of streams, usually with a peaty or mucky substrate, occasionally sandy to gravelly
Elevation 0–100 m (0–300 ft)
Distribution
from FNA
AL; FL; GA; LA; MD; MS; NC; SC; TX
[WildflowerSearch map]
from USDA
Worldwide except Antarctica
[BONAP county map]
Discussion

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. FNA vol. 22. Authors: Ralph E. Brooks*, Steven E. Clemants*.
Parent taxa Juncaceae > Juncus > subg. Ensifolii Juncaceae
Sibling taxa
J. acuminatus, J. acutiflorus, J. acutus, 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. 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. subg. Alpini, J. subg. Ensifolii, J. subg. Genuini, J. subg. Graminifolii, J. subg. Juncus, J. subg. Poiophylli, J. subg. Septati
Synonyms J. echinatus, J. engelmannii
Name authority Michaux: Flora Boreali-Americana 1: 192. 1803 (as polycephalos) 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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