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Tall boneset flowerheads are tiny (1/8" across) with no ray florets and typically only five disc florets. Disc florets are dull white with a tubular corolla and a long bifurcated style that extends well away from the floret; the base of the style is greenish and surrounded by five brown stamens with white tips. The apex of the corolla has five prominant, triangular lobes that give the florets a star-like appearance.

Eupatorium

Eupatorium altissimum

tall boneset [Blooms: Aug-Oct]

Common boneset's upper stem and branches bear clusters 2-8" across of white flowerheads. Each flowerhead is about 4-6 mm across consisting of ~15-20 dull white disk florets (ray florets are absent); florets have a tubular corolla with five triangular lobes at the apical end and a long, bifurcated style surrounded at its base with a brown column of five stamens with purplish anthers. Ironically, "common" boneset is less common than late boneset or tall boneset in Jackson Park.

Eupatorium

Eupatorium perfoliatum

common boneset [Blooms: Jul-Aug]

Late boneset's inflorescence is a flat-topped or shallowly-domed panicle with numerous flowerheads. Individual flowerheads are composed of 12-15 greyish-white disk floret (ray florets are absent) about 1/4" long with a tubular corolla with five small, triangular apical lobes and a long white bifurcated style extending well out from the floret surrounded by five black stamens. Leaf venation, lack of leaf hairs, and and smaller flowerheads (~5-8 florets) distinguish tall bonset (E.altissium) from late boneset (E. serotinum; 12-15 florets).

Eupatorium

Eupatorium serotinum

late boneset [Blooms: Aug-Oct]