Sedges differ from grasses by having a 3-angled stem and structurally different flowers where the female flowers are enclosed in a sac like structure called the perigynium, which is subtended by a single scale. Soft Fox Sedge is a perennial clump-forming sedge, growing to 30+ inches high, but on thin (to 3.5 mm), weak, unbranched stems (culms) with somewhat rough surfaces, with convex sides forming wings on the angles. With mature fruit the stem is frequently leaning if not prostrate.

The leaf sheaths usually all have blades, the fronts rugose (cross-puckered), whitish to green, red-brown spotted (variable); with the apex convex, translucent and colorless; thin, fragile. Ligules of leaf blades are rounded, 7 mm long (longer than wide) with up to .5 mm free. Basal sheaths of the previous year are usually persistent as long fibers.

The leaf blades are not more than 8 mm wide in this species and to (rarely) 75 cm (30 inches) long, but often around 18 inches long, but they do exceed the stem length, V to M shape when young, thin and soft, without hair, green in color.

The inflorescence is a terminal dense cylindric elongated cluster of spikes, up to 3 to 7 cm long and 2 cm wide, with as many as 8 to 12 spikes, the lower spikes distinct from each other and the lowest having a small separation from the adjacent of up to 15 mm. The spikes are androgynous, that is with a staminate florets at the top and the pistillate florets below. The staminate are few in number. The perigynia are spreading to ascending when developed. (The bladder-like sacs that enclose the female flower and later the fruit are called perigynia, singular - perigynium). The bracts that form at the base of the lower spikes are thin and bristle-like, but visually apparent. These are usually without sheaths. The lower bract shorter than the inflorescence.

Each perigynium is veinless on the front side, weakly 3 to 5 green veined, on the back side. The body is green, ovate in shape, 4.5 x 3 mm, flat on one side, 3 to 5 prominent green veins on back side, none on the front, with the base spongy, but not distended, and rounded to a short 0.3 mm stipe (stalk). The top tapers to a rough beak, half as long as the body. The scales of the pistillate perigynia are smooth, translucent (whitish). There are two stigmas per pistillate floret.

Seed: Mature fruit is a brown ovate achene with a smooth surface, with a persistent style base. Each is about 2.2 mm long by 1.4 mm wide. Florets are wind pollinated. Seeds require 60 days of cold stratification for germination.

Habitat: Soft Fox Sedge grows a short rhizomatous root systems, forming clumps in wet to wet-mesic conditions such as in wet and open thickets, wet meadows, edges of riparian areas and wet woods and disturbed areas. Plants prefer full sun but will grow in partial sun to shade.

Names: The genus name, Carex, is from the Latin, being the old name for Sedges. The species, conjuncta, means 'joined', referring to the crowded spike clusters of the inflorescence. The author name for the plant classification - ‘Boott’ refers to Francis Boott (1792-1863) American physician and botanist, a founder of Lowell MA. His best known work was a large folio titled Illustrations of the Genus Carex, published in 4 parts in London 1858-1867.

The various common names using the words 'fox sedge', which have also been applied to several other species, refers to the resemblance of the inflorescence to a foxes tail.

Comparisons: Soft Fox Sedge is a member of the sedges Section Vulpinae, and has the distinguishing characteristics of fairly wide V-shaped leaf blades, clump-forming short rhizomatous roots, stem bases usually black or brown, raceme type inflorescences with multiple condensed spikes, spikes usually androgynous with lower spikes sometimes pistillate only, 2 stigmas per floret.

The most similar sedges like this, found in Minnesota, are first, C. stipata, the Awl-fruit Sedge, where the sheath fronts are also rugose, the achenes are also ovate but the perigynia are veined on the front side and distended at the base and the stems have wings on the angles. Then there is C. alopecoidea, the Brown Head Foxtail Sedge where the sheath fronts are smooth, not rugose; the achenes are circular not ovate, and the perigynia are weakly veined on the back. Unlike C. conjuncta, however, C. alopecoidea is widespread in Minnesota. Another similar sedge is C. crus-corvi, Raven's-foot Sedge, where the sheath fronts are smooth, the perigynia larger 6 to 8 mm - and they are prominently distended at the base. This sedge is also scarce - known only in Goodhue and Wabasha Counties. Another closely-resembling species, but not in this sedge section, is C. vulpinoidea, Brown Fox Sedge. This has wide distribution in Minnesota. The stems are not as tall but stiff and not winged, the sheath fronts are rugose and spotted red-brown or pale brown, the leaves are narrow but longer than the flowering stem, the inflorescence is longer and has the lower spikes distinctly separated with needle-like long bracts. The perigynia, which are much smaller, take on a brown color as they are green to pale brown with pale brown scales and they have much shorter beaks.