Cape Sable Thoroughwort

Chromolaena frustrata now grows in the Everglades National Park, Long Key State Recreation Area, Lignumvitae Key State Botanical Site, and two unprotected sites. The historical range includes more sites on the Keys.

Perennials, 15–25 cm . Stems erect, puberulent to hispidulous. Petioles 5–12 mm. Leaf blades (3-nerved) elliptic-lanceolate to ovate-lanceolate or deltate-ovate, mostly 1.5–4 × 0.7–2.2 cm, margins shallowly dentate to serrate. Heads usually in clusters of 2–6. Involucres cylindric, 5.5–7.5(–8) mm. Phyllaries in 4–6 series, apices of the inner appressed, rounded (not petaloid or expanded). Corollas blue to lavender.

Eupatorium frustratum B. L. Robinson, Proc. Amer. Acad. Arts 47: 193. 1911; Osmia frustrata (B. L. Robinson) Small