Rushes
Juncus
Identification Notes: For identification of most rushes, it is important to collect plants with mature capsules and seeds. Stamen number is often a diagnostic character and can be determined after anthesis by counting the number of persistent filaments located behind the tepals. Care must be taken to collect specimens with uninjured heads, especially for the group of rushes in Key D; the long beaks of the capsules are often fragile and easily broken off.
1 Inflorescence appearing lateral; inflorescence bract erect, appearing to be a continuation of the culm .......................................... Key A1 Inflorescence appearing terminal; inflorescence bract not appearing to be a continuation of the culm.
2 Leaf blades non-septate .................................................................................................................................................................... Key B
2 Leaf blades septate (rest leaf on hard surface and run fingernail over it lengthwise).
3 Mature seeds distinctly tailed with elongate appendages at each end (may be obscure in Woodland Rush), seeds 0.7-2.5mm
long................................................................................................................................................................................................ Key C
3 Mature seeds without appendages, < 0.7mm long.
4 Flowers solitary (rarely up to 3) along branches of inflorescence; flowers often aborted; inflorescence diffuse, with slender flexuous
branches ............................................................................................................................................................ Brown-fruited Rush
4 Flowers in heads (glomerules) of 3 or more; flowers seldom aborted; inflorescence various.
5 Heads spherical or nearly so, usually 15-60 flowered ........................................................................................................... Key D
5 Heads turbinate to hemispherical, 3-15 flowered .................................................................................................................. Key E
1 At least a few sheaths at base of plant with well developed blades; inflorescence bract channeled on one side............... Leathery Rush
1 Sheaths at base of plant bladeless; bract not channeled.
2 Stems coarsely grooved, with 10-20 ridges just below inflorescence, firm; perianth 2.7-3.6mm long, sepals slightly exceeding petals
and capsule ........................................................................................................................................................................ Common Rush
2 Stems finely grooved, with 25-30 striations just below inflorescence, soft, easily compressed; perianth 1.9-2.8mm long, sepals
equaling petals ............................................................................................................................................................................ Soft Rush
1 Flowers borne in heads (glomerules) of 2 or more, individual flowers not subtended by two bracteoles (in addition to the bracteole at the
base of the pedicel).
2 Fruiting head usually congested, (1.8-)2.4-4.7(-6.4)cm long; greatest distance between adjacent rhizome scales (5.3-)6.3-10.5(-13.0)mm;
rhizome width (measured between adjacent scales) (0.8-)1.0-1.4(- 1.9)mm ....................................................................... Long's Rush
2 Fruiting head usually loose, (1.4-) 17.9-103.9 (-145) cm long; greatest distance between adjacent rhizome scales (0.1-)0.4-3.0(-4.6)mm;
rhizome width (measured between adjacent scales) (0.4-)1.0-3.5(-4.5)mm.
3 Widest leaf blade (2.6-)3.1-4.5(-5.4)mm wide; sheath of lowest leaf (3.2-)4.3-7.8(-9.7)cm long; tallest culm (27.2-)50.8-81.2(-100.7)cm;
anthers (0.5-)0.6-1.0(-1.3)mm long, exserted; stem base (3.4-)5.8-9.6(-12.0)mm wide ....................................................... Bog Rush
3 Widest leaf blade (1.3-)1.6-2.6(-3.5)mm wide; sheath of lowest leaf (1.7-)2.2-3.8(-4.7)cm long; tallest culm (19.2-)26.0-44.0(-56.8)cm;
anthers (0.2-)0.3-0.5(-0.7)mm long, concealed by tepals; stem base (0.4-)2.0-4.4(-6.0)mm wide ...................... Grass-leaved Rush
1 Flowers borne singly on branches of inflorescence, individual flowers subtended by two bracteoles (in addition to the bracteole at the base
of the pedicel).
4 Plants annual, without coarse roots or persistent leaf bases ...................................................................................................... Toad Rush
4 Plants perennial, with coarse roots or persistent leaf bases.
5 Auricles 3-6 mm long at summit of leaf sheath.
6 Capsules less than 3/4 length of perianth, borne widely spaced along the usually diffuse branches of the inflorescence .....................
................................................................................................................................................................................ Tall Slender Rush
6 Capsules more than 3/4 length of perianth, borne congested on branches with internodes about as long as perianth ......................
....................................................................................................................................................................................... Slender Rush
5 Auricles less than 2mm long or absent.
7 Cauline leaves present in addition to basal leaves; blades flat ................................................................................ Saltmarsh Rush
7 Cauline leaves absent.
8 Leaf blades terete or channeled ................................................................................................................................. Forked Rush
8 Leaf blades flat.
9 Inflorescence bract shorter than inflorescence; capsules 3-locular................................................................... Lop-sided Rush
9 Inflorescence bract longer than inflorescence; capsules 1-locular to falsely 3-locular........................................... Forked Rush
1 Culms and leaves scabrid, gray-green or blue-green; seeds 2.0-2.5mm long .................................................................. New Jersey Rush
1 Culms and leaves smooth, green; seeds 0.7-2.2mm long.
2 Seeds 1.2-2.2mm long, seed body less than ½ length of seed........................................................................................... Canadian Rush
2 Seeds 0.7-1.2mm long, seed body more than ½ length of seed.
3 Perianth obtuse to subacute, with wide scarious margins ...................................................................................... Small-headed Rush
3 Perianth acuminate, with narrow scarious margins...................................................................................................... Woodland Rush
1 Plants strictly cespitose, without any short, hard, knotty rhizomes; tepals lanecolate ................................................ Sharp-fruited Rush
1 Plants with at least some short, hard, knotty rhizomes; tepals lanceolate-subulate.
2 Capsules shorter than the tepals, clearly included within the tepals at maturity ..................................................... Short-fruited Rush
2 Capsules equaling or exceeding the tepals, exserted from or only barely included within the tepals at maturity.
3 Capsule valves separating at the apex at maturity; stamens 6........................................................................................... Torrey's Rush
3 Capsule valves remaining united at the apex after dehiscence; stamens 3................................................................. Scirpus-like Rush
1 Stamens 6.
2 Proximal stem leaf overtopping inflorescence; culms well spaced along creeping rhizomes; plants often exceed 80cm tall .................
............................................................................................................................................................................................. Bayonet Rush
2 Proximal stem leaf shorter than inflorescence; plants cespitose; plants less than 80cm tall.
3 Mature capsules slightly shorter than to slightly longer than perianth (less than 0.5mm longer); perianth 2.6-3.9mm long;
inflorescence 4-16cm long ................................................................................................................................... Sharp-fruited Rush
3 Mature capsules exceeding perianth by about 1mm (more than 0.5mm longer); perianth 1.7-3.0mm long; inflorescence 2-8cm
long .................................................................................................................................................................................. Jointed Rush
1 Stamens 3.
4 Mature capsules about 1/3 longer than perianth (roughly 1-1.5mm longer) .......................................................................... Weak Rush
4 Mature capsules equaling or barely exceeding perianth........................................................................................... Sharp-fruited Rush