OregonFlora: Juncus tiehmii vs. Juncus gerardi

	Juncus tiehmii	Juncus gerardi
	Tiehm's dwarf rush	black grass, Gerard's rush, mud rush, saltmeadow rush
Habit	Plants annual, 0.5–6 cm tall, unbranched.
Leaves	capillary; basal.
Inflorescences	1–4(7) flowers in a terminal cluster; flowers subtended by 2 bractlets; tips acute.
Flowers	tepals usually 4, pale green or pink; stamens 2(3); filaments 0.6–0.9 mm; anthers 0.3–0.4 mm; styles 0.1– 0.3 mm.
Capsules	usually elliptic to oblong, equaling or longer than the tepals, pale green or pink.
Seeds	up to 7 per chamber, 12–30 per capsule, 0.3–0.5 × 0.2–0.3 mm, longitudinally striate (at 10×).
2n	=34.

	Juncus tiehmii	Juncus gerardi
Distribution	[BONAP county map]	[WildflowerSearch map] [BONAP county map]
Discussion	Damp depressions, stream banks, sunny floodplains. 1000– 2000m. BR, ECas. CA, NV, ID, WA; south to Mexico. Native. Plants with few seeds per capsule have larger seeds, and thus some specimens might suggest J. capillaris, but there is no overlap. Juncus capillaris always has fewer than 10 seeds per capsule.	[Species with one variety or subspecies in Oregon.]
Source	Flora of Oregon, volume 1, page 284 Peter Zika	Flora of Oregon, volume 1
Sibling taxa	J. acuminatus, J. anthelatus, J. articulatus, J. balticus, J. bolanderi, J. brevicaudatus, J. breweri, J. bryoides, J. bufonius, J. bulbosus, J. canadensis, J. capillaris, J. capitatus, J. compressus, J. confusus, J. conglomeratus, J. covillei, J. diffusissimus, J. drummondii, J. dudleyi, J. effusus, J. ensifolius, J. ensifolius x Juncus nevadensis, J. exiguus, J. falcatus, J. filiformis, J. gerardi, J. hemiendytus, J. hesperius, J. howellii, J. inflexus, J. interior, J. kelloggii, J. laccatus, J. lescurii, J. longistylis, J. marginatus, J. mertensianus, J. mexicanus, J. nevadensis, J. occidentalis, J. orthophyllus, J. oxymeris, J. parryi, J. patens, J. pelocarpus, J. planifolius, J. ranarius, J. regelii, J. saximontanus, J. supiniformis, J. tenuis, J. torreyi, J. triglumis, J. trilocularis, J. uncialis	J. acuminatus, J. anthelatus, J. articulatus, J. balticus, J. bolanderi, J. brevicaudatus, J. breweri, J. bryoides, J. bufonius, J. bulbosus, J. canadensis, J. capillaris, J. capitatus, J. compressus, J. confusus, J. conglomeratus, J. covillei, J. diffusissimus, J. drummondii, J. dudleyi, J. effusus, J. ensifolius, J. ensifolius x Juncus nevadensis, J. exiguus, J. falcatus, J. filiformis, J. hemiendytus, J. hesperius, J. howellii, J. inflexus, J. interior, J. kelloggii, J. laccatus, J. lescurii, J. longistylis, J. marginatus, J. mertensianus, J. mexicanus, J. nevadensis, J. occidentalis, J. orthophyllus, J. oxymeris, J. parryi, J. patens, J. pelocarpus, J. planifolius, J. ranarius, J. regelii, J. saximontanus, J. supiniformis, J. tenuis, J. tiehmii, J. torreyi, J. triglumis, J. trilocularis, J. uncialis
Subordinate taxa		J. gerardi ssp. gerardi
Web links	Local floras: CA, OR, WA Local Web sites: CalFlora, CalPhotos, Flora NW, PNW Herbaria WildflowerSearch iNaturalist (observations) USDA Plants Database LBJ Wildflower Center SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search	Local floras: BC, OR, WA Local Web sites: Flora NW, PNW Herbaria WildflowerSearch iNaturalist (observations) USDA Plants Database LBJ Wildflower Center SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search

Juncus tiehmii

Juncus gerardi

Tiehm's dwarf rush

black grass, Gerard's rush, mud rush, saltmeadow rush

Habit

Plants annual, 0.5–6 cm tall, unbranched.

Leaves

capillary;

basal.

Inflorescences

1–4(7) flowers in a terminal cluster;

flowers subtended by 2 bractlets;

tips acute.

Flowers

tepals usually 4, pale green or pink;

stamens 2(3);

filaments 0.6–0.9 mm;

anthers 0.3–0.4 mm;

styles 0.1– 0.3 mm.

Capsules

usually elliptic to oblong, equaling or longer than the tepals, pale green or pink.

Seeds

up to 7 per chamber, 12–30 per capsule, 0.3–0.5 × 0.2–0.3 mm, longitudinally striate (at 10×).

=34.

Juncus tiehmii

Juncus gerardi

Distribution

[BONAP county map]

[WildflowerSearch map]

[BONAP county map]

Discussion

Damp depressions, stream banks, sunny floodplains. 1000– 2000m. BR, ECas. CA, NV, ID, WA; south to Mexico. Native.

Plants with few seeds per capsule have larger seeds, and thus some specimens might suggest J. capillaris, but there is no overlap. Juncus capillaris always has fewer than 10 seeds per capsule.

[Species with one variety or subspecies in Oregon.]

Source

Flora of Oregon, volume 1, page 284
Peter Zika

Flora of Oregon, volume 1

Sibling taxa