Flower:

3 to 35 flower heads in a compact or open branching cluster at the top of the stem, the branches mostly erect, the lower branches subtended by an erect, leaf-like bract that does not overtop the cluster. Each flower head is 2 to 9 mm in diameter with 2 to 8 flowers, mostly inverted cone-shaped in outline. Flowers have 6 tepals (petals and similar sepals) in 2 layers, the outer tepals 2.3 to 3.1 mm long and usually slightly shorter than the inner tepals, both sharply pointed at the tip and green to orange-brown with narrow, white, papery edging. Flowers have a 3-parted style and usually 3 stamens, sometimes 6, the anthers (tips) ¼ to ½ as long as the filament (stalk).

Leaves and stems:

A flowering stem has 1 or 2 alternate leaves and 1 to 3 basal leaves. Leaves are ½ to 10 inches long, up to 2.5mm wide, round in cross-section, with cross partitions (septa) at regular intervals (may be easier felt than seen). The sheath is open at the front. At the tip of the sheath is a pair of lobes (auricles) .5 to 3 mm long, rounded or straight across at the tip with a papery band around the edge. Stems are smooth, erect, unbranched, a few from the base forming small, loose clumps.

Fruit:

Fruit is a 3-sectioned capsule 3.2 to 4.8 mm long, usually much longer than the tepals, tapering to a pointed tip, maturing to chestnut brown. Inside are numerous spindle-shaped seeds with short, pale, tail-like appendages at both ends. Seeds are .7 to 1.2 mm long including the tails, with a white translucent covering.

Notes:

Narrow-panicled Rush is a wetland species found in Minnesota from the Metro area north. Only two other Juncus species in Minnesota have tailed seeds: Juncus canadensis and Juncus vaseyi. J. canadensis has longer tails on the seeds, flower heads typically with more than 8 flowers (up to 50), hemisheric to round heads, widely spreading branches, and the capsules are not usually much longer than the tepals. J. vaseyi flowers are single, not clustered in heads and usually not more than 15 in a cluster, it does not have septate leaves, the capsules are greenish and not pointed at the tip.

J. brevicaudatus also resembles 2 other Minnesota Juncus species with septate leaves and usually fewer than 10 flowers in a head: Juncus alpinoarticulatus and Juncus articulatus. The tepals and capsules are all slightly different between the three, with J. brevicaudatus capsules and tepals both longer, proportionately narrower and all tapering to sharply pointed tips, J. articulatus capsules and tepals also all with pointed tips but proportionately broader than J. brevicaudatus, and J. alpinoarticulatus capsules more distinctly rounded at the tip, the inner tepals usually blunt to rounded, and the capsule not extending more than .5mm beyond the tips of the tepals, where the other two both extend about 1mm.