Flora of North America species comparison

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Juncus gerardii

Juncus subg. Poiophylli

black needle rush, blackgrass, blackgrass rush, Gerard's rush, saltmarsh rush, saltmeadow rush
Habit Herbs, perennial, 2–9 dm. Herbs, perennial, rarely annual, perennials rhizomatous.
Rhizomes

long- creeping.

Stems

terete.
Cataphylls

1–3.

Leaves

basal, (1–)2–4;

auricles 0.4–0.6(–0.8) mm, scarious;

blade flat or somewhat channeled, 10–40 cm × 0.4–0.7 mm, margins entire.

basal and cauline;

blade usually flat, involute, rarely nearly terete, channeled, not septate.
Inflorescences

10–30(–80)-flowered, usually loose and somewhat lax, 2–16 cm;

primary bract rarely surpassing inflorescence.

terminal cymes, usually sympodial (monopodial in J. trifidus);

bracts erect or ascending, flat, involute, or terete;

bracteoles 2, at base of perianth.
Flowers

bracteoles 2;

tepals dark brown or blackish, lanceolate-ovate to oblong, 2.6–3.2(–3.8) mm;

inner and outer series nearly equal, apex obtuse;

stamens 6, filaments 0.4–0.7 mm, anthers 1.1–1.6(–1.8) mm;

style 0.4 mm.

borne singly, not in heads.
Capsules

chestnut brown or brown, 3-locular, widely ellipsoid, (2.2–)2.5–3.2(–3.5) × 1.3–1.9 mm.

1-locular (placentae 1/2–3/4 distance to central axis) or 3-locular, rarely beaked.
Seeds

dark brown, ellipsoid to lunate, 0.485–0.6(–0.67) mm, not tailed.

not tailed (except J. vaseyi).
2n

= ca. 80, 84.

Juncus gerardii

Juncus subg. Poiophylli
Phenology Flowering and fruiting late spring–summer.
Habitat Forming extensive colonies in exposed coastal estuary meadows and salt marshes just above high- tide line, also inland
Distribution
from FNA
CO; CT; DE; IL; IN; KS; KY; MA; MD; ME; MI; MN; MO; MT; ND; NH; NJ; NY; OH; OR; OR; PA; RI; UT; VA; VT; WA; WI; BC; MB; NB; NF; NS; ON; PE; QC; SPM; Greenland; Europe; Asia
[WildflowerSearch map]
Worldwide
Discussion

Species 25 (18 in the flora).

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key
1. Plants annual
J. bufonius
1. Plants perennial.
→ 2
2. Leaves minutely serrulate; auricles deeply lacerate
J. trifidus
2. Leaves entire; auricles not lacerate.
→ 3
3. Auricles at summit of leaf sheath 3–6 mm, membranous, transparent; capsules never 3-locular.
→ 4
3. Auricles absent or merely short, scarious or cartilaginous projections less than 2 mm.
→ 5
4. Capsules less than 3/4 length of tepals, borne widely spaced along usually diffuse branches of inflorescence; plants mostly 7–9 dm
J. anthelatus
4. Capsules 3/4 or more length of tepals, borne congested or branch internodes ca. as long as tepals; plants mostly less than 7 dm
J. tenuis
5. Leaf blade channeled to terete.
→ 6
5. Leaf blade flat.
→ 10
6. Inflorescence falsely lateral, overtopped by terete bract that looks to be continuation of culm
J. coriaceus
6. Inflorescence terminal, involucre bract flat or much shorter than inflorescence.
→ 7
7. Perianth segments obtuse
J. squarrosus
7. Perianth segments acute to acuminate.
→ 8
8. Seeds distinctly tailed, tail at least 1/2 length of seed body; capsules golden tan
J. vaseyi
8. Seeds not tailed; capsules chestnut brown or paler.
→ 9
9. Capsules 1-locular or pseudo-3-locular, widely elliptic to rounded, apex rounded; seeds 0.3–0.4 mm
J. dichotomus
9. Capsules 3-locular, elliptic, apex somewhat truncate; seeds 0.48–0.7 mm
J. greenei
10. Capsules chestnust brown or darker; tepals apically obtuse or rounded.
→ 11
10. Capsules tan or light brown; tepals acute to acuminate.
→ 12
11. Anther 1–2 times length of filament, less than 1 mm; capsule usually exceeding perianth
J. compressus
11. Anther 2–4 times length of filament, longer than 1 mm; capsule usually nearly equal to perianth
J. gerardii
12. Capsules 3-locular.
→ 13
12. Capsules 3-locular or pseudo-3-locular.
→ 16
13. Tepals 2.5–3.5 mm; capsule nearly globose.
→ 14
13. Tepals 4–5.5 mm; capsule ellipsoid to narrowly so.
→ 15
14. Tepals green; flowers chiefly arranged along inner side of branches; plants of e North America
J. secundus
14. Tepals usually with brownish midstripe; flowers not secund; plants of w North America
J. confusus
15. Anthers 0.6–0.9 mm; auricles scarious, lobes 0.5 mm; plants of c United States
J. brachyphyllus
15. Anthers 1.2–1.5 mm; auricles scarious to membranous, 0.2–0.3 mm; plants endemic to s Appalachian Piedmont
J. georgianus
16. Auricles 0.5–1(–1.5) mm, membranous
J. occidentalis
16. Auricles 0.1–0.3(–1) mm, scarious to leathery.
→ 17
17. Auricles leathery, yellowish; tepals spreading in fruit, nearly equal to or exceeding capsule; anthers 0.6–1 mm
J. dudleyi
17. Auricles scarious, whitish or sometimes purplish tinged, not leathery; anthers 0.4–0.6 mm.
→ 18
18. Mature capsules light brown or darker; plants of coastal plain of e, se North America
J. dichotomus
18. Mature capsules light tan; plants of interior continent
J. interior
Source FNA vol. 22. FNA vol. 22.
Parent taxa Juncaceae > Juncus > subg. Poiophylli Juncaceae > Juncus
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. 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. anthelatus, J. brachyphyllus, J. bufonius, J. compressus, J. confusus, J. coriaceus, J. dichotomus, J. dudleyi, J. georgianus, J. gerardii, J. greenei, J. interior, J. occidentalis, J. secundus, J. squarrosus, J. tenuis, J. trifidus, J. vaseyi
Synonyms J. bulbosus var. gerardii, J. fucensis, J. gerardii var. pedicellatus J. section Poiophylli, J. subg. Pseudo-tenageia, J. section Tenageia, J. subg. Tenageia
Name authority Loiseleur-Deslongchamps: J. Bot. (Desvaux) 2: 284. (1809) Buchenau: Abhandlungen herausgegeben vom naturwissenschaftlichen Vereine zu Bremen 4: 406. (1875)
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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