Flower:

2 to 10 flower heads in a branching cluster at the top of the stem, the heads at branch tips, the branches mostly erect, the lower branches subtended by an erect, scale-like bract up to ¾ inch long. Each flower head is up to 15 mm in diameter, mostly inverted cone-shaped in outline, with 3 to 8 erect flowers. Sometimes the heads are all congested at the tip of the stem.

Flowers have 6 tepals (petals and similar sepals) in 2 layers, the outer tepals 5 to 6 mm long and more or less as long as the inner tepals, both sharply pointed at the tip, dark chestnut brown with a broad dark green midstripe, and broad, translucent whitish to light brown edging. Flowers have a 3-parted style and 6 stamens, the anthers (tips) about twice as long as the filament (stalk) and the whole stamen half or so as long as the tepals. At the base of each flower is an appressed to spreading, translucent whitish, broad papery bract half to about as long as the tepals that dries to brown. 

Leaves and stems:

A flowering stem has 2 to 5 basal leaves and 1 to 3 alternate leaves on the lower stem. Leaves are 4 to 12 inches long, 1.5 to 3mm wide, flat, the stem leaves much shorter than the basal leaves and all shorter than the flowering stem. The sheath is open at the front. At the tip of the sheath is a pair of lobes (auricles) 1 to 2.5 mm long, rounded or straight across at the tip with a papery band around the edge. Stems are smooth, erect, unbranched, round to slightly flattened in cross-section, single from the base forming scattered colonies from long, creeping rhizomes.

Fruit:

Fruit is a 3-sectioned capsule maturing to dark chestnut brown, more or less as long as the tepals, rounded to nearly flat at the tip with an abrupt taper to a beak .5 to 1 mm long. Inside are numerous oval-elliptic seeds, .4 to .6 mm long, brown with network of fine ridges across the surface and a white translucent covering, abruptly pointed on one end and with a short, whitish appendage at the other.

Notes:

Juncus longistylis is an occasional species of moist prairie swales, sedge meadows and ditches, and reaches the eastern edge of its range in Minnesota. Whenever we've encountered it, it has not been in any great abundance, but just scattered plants mostly hidden amongst the other tall grasses and grass-like plants. The combination of flat leaves, large tepals (5 to 6mm long) with a broad, dark green and brown midstripe and broad translucent edging, the distinct beak on the capsules, plus the fairly conspicuous bract subtending each flower are pretty distinctive and distinguish this from other Juncus species in MN. The tepals somewhat resemble those of Junus marginatus (Grassleaf Rush), a very rare species of the Anoka Sandplain that has tepals only about half as long and capsules are not beaked. Of note is some references state the inner tepals of J. longistylis are slightly longer than the outer, but the specimens we encountered showed the opposite to be true. In either case they are nearly equal in size.