Flower:

5 to 25 flower heads in a branching cluster at the top of the stem, the cluster longer than wide, the branches erect to ascending, the lower branches subtended by an erect, leaf-like bract that may overtop the cluster but usually not. Each flower head is 2 to 6 mm in diameter with 2 to 10 flowers, inverted cone-shaped to hemispheric in outline. Flowers have 6 tepals (petals and similar sepals) in 2 layers, the outer tepals 1.8 to 3 mm long and pointed at the tip, the inner tepals about as long or slightly shorter and usually blunt to rounded at the tip, and both chestnut brown with a green to straw-colored midrib and a narrow band of, white, papery edging. Flowers are stalkless to short-stalked, have a 3-parted style and 6 stamens, the anthers (tips) half as long as the filament (stalk).

Leaves and stems:

A flowering stem has 1 or 2 (rarely more) alternate leaves and 0 to 3 basal leaves. Leaves are ½ to 4¾ inches long, up to 1.1mm 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 1.2 mm long, rounded at the tip with a membranous band around the edge. Stems are smooth, erect, unbranched except in the flower cluster, forming loose clumps and colonies from creeping rhizomes.

Fruit:

Fruit is a 3-sectioned capsule 2.3 to 3.5 mm long, about as long as the tepals or extending beyond them up to .5mm, mostly rounded at the tip, maturing to dark chestnut brown. Inside are numerous seeds, oblong-elliptic to egg-shaped, narrowed at the tip, .5 to .7 mm long, maturing to dark golden brown, and with a wrinkly texture.

Notes:

Northern Green Rush is a common species in Minnesota, found in a variety of wet habitats including sandy shores, peaty sedge meadows, calcareous fens, and on the rocky north shore of Lake Superior. It has a circumpolar distribution, across northern latitudes and alpine regions of Europe, Asia and North America. It is also a variable species and some studies propose as many as 6 varieties or subspecies, but there is no consensus so none of these are recognized in Minnesota at this time.

Juncus alpinoarticulatus, formerly Juncus alpinus, most closely resembles 2 other Juncus species in Minnesota: Juncus brevicaudatus 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 though 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. J. brevicaudatus is also distinguished by its seed with a distinct elongated “tail” at each end, which the other two lack. The non-native Juncus compressus is somewhat similar but its flowers are all single at branch tips, not in heads of 2 or more.