Coelestina
(from coelestis, celestial; in reference to the blue-coloured flowers). ORD. Compositae. This genus is now merged into Ageratum. Half-hardy, showy, herbaceous perennials. Pappus a membranous rim; involucre cylindrical, many-leaved, imbricated; receptacle convex, naked; florets all tubular. They are of easy culture in ordinary garden soil. Propagated by seeds and cuttings, which are easily managed in gentle warmth, in spring. C. ageratoides (Ageratum-like).* fl.-heads blue. July to October. l. stalked, ovate, acute, rounded at base, serrated, pilose above, hairy beneath. h. 1ft. New Spain.
Other species are coerulea and micrantha, both blue-flowered, and natives of America; but they are scarcely worth growing.