[Ageratum corymbosum elachycarpum (B. L. Rob.) M. F. Johnson, moreAgeratum corymbosum var. jaliscense , Ageratum elachycarpum B. L. Rob., Ageratum guatemalense M.F. Johnson, Eupatorium coeruleum Sessé & Moc.]
Perennials or subshrubs, 30-100 cm (fibrous-rooted). Stems erect to basally decumbent, puberulent to minutely strigoso-hispid. Leaf blades ovate to rhombic-lanceolate, 3-8 × 1-3.5 cm, margins toothed, abaxial faces usually puberulent, sometimes minutely strigoso-hispid, densely gland-dotted. Peduncles finely puberulent (not pilose), eglandular. Involucres 5-6 mm. Phyllaries narrowly lanceolate (0.4-0.7 mm wide, innermost often 1-1.5 mm longer than outer), finely puberulent, eglandular, tips green or purplish, filiform. Corollas usually blue to lavender, sometimes white. Cypselae glabrous; pappi usually crowns of connate scales with erose margins or tubular portions longer than divisions, rarely with 1 or more awnlike lobes. 2n = 20, 30, 40. Flowering Jul-Oct. Crevices, ledges, cliffs, other rocky sites in canyons, along streams, in desert grasslands, oak-agave, oak, oak-juniper, and pine-oak woodlands; (900-)1200-1900 m; Ariz., N.Mex.; Mexico.