[C. solstitialis sensu Hawaiian botanists, non L.]
(nat) Napa thistle, yellow star thistle
Annual or biennial herbs; stems several from the base, 1—5(—8) dm long, branched in upper part. Leaves oblanceolate in outline, 5-10 cm long, pinnately lobed, upper leaves nearly linear, 1-3 cm long, base decurrent, forming narrow wings on the stem. Heads in the upper leaf axils; involucre nearly globose, the bracts very firm, often arachnoid pubescent near the tip when young, abruptly constricted at apex to a sharp spreading tip 3-9 mm long, each margin with several very short spines near base of tip; corollas yellow, 8-10 mm long; pappus of bristles in several series, 3-4 mm long. Achenes attached at a lateral notch slightly above the base. [2n = 22, 24, 36.] Native to Europe; in Hawaii naturalized in low elevation, dry habitats on all of the main islands. Naturalized prior to 1871 (Hillebrand, 1888).—Plate 20.
Centaurea maculosa Lam. has been collected once at Kona, Hawaii, in 1965 (State Department of Agriculture s.n., BISH). It differs from C. melitensis in its pinkish purple . corolla, involucral bracts not spine-tipped, and pappus only up to 2 mm long or absent.