22. Carex praegracilis W. Boott (freeway sedge)

Pl. 35 a–e; Map 135

Plants monoecious or sometimes dioecious, with stout, black to brownish black rhizomes. Flowering stems 20–70 cm long, sharply trigonous, roughened on the angles toward the tip. Leaf blades 10–25 cm long, 1–3 mm wide, thick, straight or somewhat arching. Leaf sheaths somewhat thickened at the tip. Heads 10–50 mm long, cylindrical, the 5–25 spikes 4–8 mm long, 4–6 mm wide, mostly with inconspicuous staminate flowers toward the tip and 8–13 perigynia toward the base, sometimes entirely staminate or pistillate. Staminate scales 3.2–4.0 mm long. Perigynia 2.9–3.9 mm long, including the 0.6–1.3 mm long beak, finely several-nerved on the ventral surface, lacking nerves on the dorsal surface, the base somewhat spongy-thickened above the stalk, straw-colored, turning dark brownish black at maturity. Fruits 1.1–1.4 mm long. 2n=60. May–July.

Introduced, known only from Jackson County and the city of St. Louis (western U.S. from Minnesota, Kansas, and Iowa west to Washington and California; Canada, Mexico, South America; introduced in the midwestern and northeastern U.S.). Adventive along railroads.

Superficially, this species resembles the native C. sartwellii (section Intermediae), but in that species the leaves are not all basally disposed, and its lower leaves are reduced to bladeless sheaths. Reznicek and Catling (1987) documented the eastward spread of C. praegracilis from its native range in the western United States and Great Plains. They noted that although most adventive occurrences prior to 1970 were along railroad tracks, more recently the species has spread rapidly along the shoulders of highways and other roads, particularly in northern areas where winter application of road deicing salt creates saline conditions, which the plants tolerate well. Although C. praegracilis has not been collected yet along roadsides in Missouri, it should be found in this habitat in the future.