OregonFlora: Juncus acutus vs. Juncus

	Juncus acutus	Juncus
		rush
Habit		Plants annual with delicate fibrous roots, or perennial herbs with coarse roots, cespitose, rhizomatous, or uncommonly stoloniferous with lax stems rooting at nodes, usually erect, glabrous.
Stems		round or flattened.
Leaves		sometimes absent, mostly basal or on lower 33% of stem; sheaths open, awned; blades linear to filiform; hollow and with chambered crosswalls, or solid and very thin to inrolled, or flattened laterally and incompletely septate (iris-like), or flattened adaxially/abaxially, glabrous, base of blade sometimes with auricles; veins parallel.
Bracts		leafy or membranous.
Inflorescences		racemose to cymose with flowers solitary or in small clusters, or in dense clusters, often head-like; pedicels with small bract at base; flowers with (0)1–2 small bractlets at base.
Flowers		perfect; tepals (4)6(8), often lanceolate; stamens (2)3 or 6; anthers shorter or longer than linear filaments; stigmas 3.
Capsules		dry, 1- or 3-chambered, usually ovoid-trigonous, sometimes crested apically, beaked or not.
Seeds		(4)10–200, 0.2–0.5(0.6)mm wide, apiculate or with a slender white tail at one or both ends.

	Juncus acutus	Juncus
Distribution	[WildflowerSearch map] [BONAP county map]	[BONAP county map]
Discussion		Cosmopolitan. 315 species; 56 species treated in Flora. Although anther characters are used in the key, flowering material is generally worthless for identification purposes and never makes an acceptable herbarium voucher. The anthers persist under the tepals into fruit, and only material with ripe capsules and mature seeds should be used in the keys. Basal parts of the shoots are critical, with similar species sometimes most easily separated by proximal sheaths or the presence or absence of long rhizomes. The key relies on delicate sheaths and auricles; these are easily damaged unless specimens are carefully dug, never pull them from the ground. Among the bladeless species (Group 2), fresh plants have varied and diagnostic stems: dull or shiny, smooth or ridged, or blue-green. This should be noted in the field and on specimen labels. Septate leaves (Group 3) are easy to recognize on live plants, by pulling a leaf between two fingertips and feeling for “bumps.” Populations of Groups 3 and 4 sometimes have a few disfigured and congested stems, induced by gall insects. Seed lengths include the tails unless otherwise specified.
Source		Flora of Oregon, volume 1, page 266 Peter Zika
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. tiehmii, J. torreyi, J. triglumis, J. trilocularis, J. uncialis
Subordinate 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. 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. tiehmii, J. torreyi, J. triglumis, J. trilocularis, J. uncialis
Web links	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	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

Juncus acutus

Juncus

rush

Habit

Plants annual with delicate fibrous roots, or perennial herbs with coarse roots, cespitose, rhizomatous, or uncommonly stoloniferous with lax stems rooting at nodes, usually erect, glabrous.

Stems

round or flattened.

Leaves

sometimes absent, mostly basal or on lower 33% of stem;

sheaths open, awned;

blades linear to filiform; hollow and with chambered crosswalls, or solid and very thin to inrolled, or flattened laterally and incompletely septate (iris-like), or flattened adaxially/abaxially, glabrous, base of blade sometimes with auricles;

veins parallel.

Bracts

leafy or membranous.

Inflorescences

racemose to cymose with flowers solitary or in small clusters, or in dense clusters, often head-like;

pedicels with small bract at base;

flowers with (0)1–2 small bractlets at base.

Flowers

perfect;

tepals (4)6(8), often lanceolate;

stamens (2)3 or 6;

anthers shorter or longer than linear filaments;

stigmas 3.

Capsules

dry, 1- or 3-chambered, usually ovoid-trigonous, sometimes crested apically, beaked or not.

Seeds

(4)10–200, 0.2–0.5(0.6)mm wide, apiculate or with a slender white tail at one or both ends.

Juncus acutus

Juncus

Distribution

[WildflowerSearch map]

[BONAP county map]

Discussion

Cosmopolitan. 315 species; 56 species treated in Flora.

Although anther characters are used in the key, flowering material is generally worthless for identification purposes and never makes an acceptable herbarium voucher. The anthers persist under the tepals into fruit, and only material with ripe capsules and mature seeds should be used in the keys. Basal parts of the shoots are critical, with similar species sometimes most easily separated by proximal sheaths or the presence or absence of long rhizomes. The key relies on delicate sheaths and auricles; these are easily damaged unless specimens are carefully dug, never pull them from the ground. Among the bladeless species (Group 2), fresh plants have varied and diagnostic stems: dull or shiny, smooth or ridged, or blue-green. This should be noted in the field and on specimen labels. Septate leaves (Group 3) are easy to recognize on live plants, by pulling a leaf between two fingertips and feeling for “bumps.” Populations of Groups 3 and 4 sometimes have a few disfigured and congested stems, induced by gall insects. Seed lengths include the tails unless otherwise specified.

Source

Flora of Oregon, volume 1, page 266
Peter Zika

Sibling taxa