2. Sisyrinchium angustifolium Mill.

Pl. 92 g; Map 355

Aerial stems 15–50 cm long, 2–6 mm wide, often broadly winged, appearing branched, not glaucous. Leaves 2–6 mm wide, not glaucous, sometimes darkening upon drying. Inflorescences 1–4 per aerial stem, from often broadly winged stalks 4–15 cm long from the axils of leaflike bracts. Spathelike bracts of each inflorescence 1.3–4.0 cm long, green, sometimes purplish tinged, mostly with the outer bract 1.5–2.0 times as long as the inner bract at flowering time. Perianth pale blue to purplish blue. 2n=48. May–July.

Scattered throughout Missouri (eastern U.S. and adjacent Canada west to Kansas). Mesic forests and stream banks, less commonly in mesic upland prairies; also in old fields, on roadsides and ditch banks, and along railroad tracks.

In Missouri, S. angustifolium can be difficult to distinguish from S. atlanticum, particularly because some of the characteristics used to separate these species in other portions of their ranges do not seem to work consistently in the state. Missouri specimens of S. angustifolium darken upon drying only sporadically, and are often a similar shade of green to those of S. atlanticum when fresh. Although the stalks of the inflorescences are broad-winged in most S. angustifolium plants, those of S. atlanticum are not always uniformly narrow-margined, as has been described elsewhere. In addition, S. atlanticum varies greatly in the degree of glaucousness, and this characteristic is often lost when plants are pressed and dried. The most reliable characters for separating the two species appear to be the overall stem width and the size relationship of the 2 spathelike bracts, as noted in the key to species above.

Ward (1968) discussed the application of S. angustifolium to our plants instead of the previously widely accepted S. bermudiana L., which is correctly applied to a species endemic to Bermuda.