Until they bloom, these little plants are nearly indistinguishable from the grass in which they grow. Even in bloom they’re easy to overlook, but they deserve a close inspection. This one was blooming in Scott in late June.
The very similar, and indeed almost indistinguishable, S. montanum is also known from Westmoreland County, but not Allegheny County; our best bet, therefore, is that this plant is S. angustifolium.
Gray describes the genus and the species (and, by the way, it seems etymologically implausible to describe the name of the genus as “meaningless,” even if we don’t happen to know what it meant):
SISYRÍNCHIUM L. BLUE-EYED GRASS. Sepals and petals (perianth) alike, spreading. Capsule globular, 3-angled. Seeds globular. — Low slender perennials, with fibrous roots, grassy or lanceolate leaves, 2-edged or winged stems, and fugacious umbeled-clustered small flowers from a usually 2-leaved spathe. (A meaningless name, of Greek origin.)
S. angustifölium Mill. Erect or ascending, stiff, glaucous, 1-5 dm. high; the simple (rarely forked) stems 1.5-3 mm. wide, distinctly winged, exceeding the scarcely broader leaves; spathes green, rarely purplish, the outer bract with margins united 3-6 mm. above the base, 2-6.5 cm. long, the inner 1-3 cm. long; perianth violet (rarely white); capsules dull brown or purple-tinged. — Meadows, fields, and damp sandy soil, Nfd. to B. C, s. to Va., Pa., Mich., Minn.; and in the Rocky Mts. May-July.
In his Field Book of American Wild Flowers, Mathews gives us this description:
A stiff grasslike little plant with linear, pale blue-green leaves less than the somewhat twisted and flat flower-stem in height. The flowers are perfect, with a prominent pistil, and three stamens; the six divisions are blunt and tipped with a thornlike point; they are violet-blue, or sometimes white; the centre of the flower is beautifully marked with a six-pointed white star accented with bright golden yellow, each one of the star-points penetrating the deeper violet-blue of the petallike division. The flower is mostly cross-fertilized by bees, and thft beelike flies (Syrphidce). Seed capsule globular. The name is Greek in origin, and is meaningless. 6-13 inches high. In fields and moist meadows, common from Me., south to Va., and west. Stem inch wide.
