This section is from the book "The Standard Cyclopedia Of Horticulture Vol2", by L. H. Bailey. See also: Western Garden Book: More than 8,000 Plants - The Right Plants for Your Climate - Tips from Western Garden Experts.
(named for an ancient king of Pontus said by Pliny to have employed one of this group of plants in medicine). Compositae. Joe-Pye Weed. Thoroughwort. Boneset. Hemp Agrimony. Mist-Flower. Chiefly perennial herbs, a few species annual, many of the tropical ones shrubby or even arborescent; some of them hardy border plants, others grown in coolhouses as florists' plants, and others in warmhouses for the attractive foliage.
Heads rayless, mostly in dense flat-topped or rounded clusters, less frequently in open panicles, the florets (rarely 1-4) mostly 5 or more in each head, perfect, the 2 style-branches long, threadlike or club-shaped, protruding far out of the tube of the floret; involucre cylindrical to hemispherical, its scales in 2 to many overlapping ranks: achenes 5-angled, crowned with a well-developed pappus of hair-like mostly white bristles: leaves mostly opposite: flowers purple, rose-colored or white, more rarely lilac or bluish violet, never yellow. - At least 600 species, chiefly of Mex., the W. Indies, and tropical S. Amer. Certain species, now botanically placed in Eupatorium, still appear in trade catalogues and seed-lists under the names Hebeclinium and Cono-clinium. Others have been confused with Ageratum.
Of this large and varied genus relatively few species have been brought into cultivation. Of these, there are two classes, namely certain warm-country species adapted only to glasshouse culture, and on the other hand a few native North American species (as well as the hemp agrimony of Europe), more or less tractable in cultivation, especially as components in making up mixed hardy borders. The glasshouse species are seen only in the larger or amateur collections, as a rule, although a few have been long in European cultivation. Of the hardy species, some, reputed medicinal, are found in old gardens. The glasshouse species demand the general treatment of Piqueria (Stevia of florists) - a cool or intermediate temperature and pot culture. They are easy to grow, and propagate readily by cuttings. They are useful for winter bloom, the heads, though individually small, being aggregated in showy masses.
a. Glasshouse or warm-country species. b. Florets pink, purple, lilac, or violet. c. Involucral scales not ending in hairy tails. d. Shape of leaves ovate; If. - stalks long. E. Leaves heart-shaped.
F. stems covered with dense reddish wool............... 1. atrorubens ff. stems green.
G. Panicle dense, terminal: leaves mucronate-toothed.. 2. megalophyllum GG. Infloresence lax, partly axillary: leaves crenate-toothed..... 3. Purpusii ee. Leaves pointed or blunt at base. . . 4. ianthinum dd. Shape of leaves lanceolate or oblong; If. - stalks short. e. Leaves alternate: heads many-flowered. 5. Lasseauxii ee. Leaves opposite: heads 5-12-flowered.. 6. serrulatum cc. Involucral scales ending in hairy, colored tails................... 7. hecatanthum bb. Florets white or nearly so (the pappus sometimes colored). c. Leaves leathery, lance-oblong, glabrous, entire.................. 8. araliaefolium cc. Leaves not leathery, usually somewhat toothed and hairy. d. leaf - blade elliptic-lanceolate, de-current and crisped on short stalk....................... 9. micranthum dd. leaf - blade round-ovate, toothed even to the decurrent base......10. conspicuum ddd. leaf - blade not decurrent on petiole. e. Plant glandular-sticky.
f. Heads about 1/4in. diam.....11. glandulosum ff. Heads about 1/2in. diam............12. probum ee. Plant not glandular-sticky. f. Leaves velvety beneath: infloresence
broad rounded corymb.....13. vernale ff. Leaves sparingly hairy or soon glabrate.
a. Shape of leaves round- or triangular-ovate; margins toothed.
h. leaf - blade small, 1/2 1 1/2 in. long........14. glechonophyllum hh. leaf - blade larger, 2-4 in. long............15. pazcuarense gg. Shape of leaves elliptic-ovate; margins nearly or quite entire...........16. glabratum ggg. Shape of leaves narrowly lanceolate.............17. riparium aa. Hardy or border plants.
b. Florets flesh-colored, reddish or bluish-purple. c. Leaves lance-oblong, merely toothed, mostly whorled................18. purpureum cc. Leaves deeply 8-parted, opposite.....19. cannabinum ccc. Leaves broadly ovate, opposite, merely toothed.......................20. coelestinum bb. Florets white or nearly so.
c. Leaves perfoliate (united around the stem)..........................21. perfoliatum cc. Leaves not perfoliate.
d. leaf - blade lanceolate, the base narrowed and scarcely stalked.
e. Scales of involucre blunt, gray-velvety...............22. altissimum ee. Scales sharp, smoothish, with thin white edge.............23. album dd. leaf - blade ovate-lanceolate, sessile by a rounded base...........24. sessilifolium ddd. leaf - blade broadly ovate, usually well stalked. e. The leaves taper-pointed, sharply toothed...................25. urticaefolium ee. The leaves mostly blunt and bluntly toothed.............26. aromaticum
(Hebeclinium atrorubens, Lem.). Leaves large, ovate, short-stalked, heart-shaped at base, opposite, toothed, covered on the edge and veins with long reddish-or claret-colored hair: heads red or purple, in a very large red-rayed truss. S. Mex. I.H. 9:310. - A stately species with fine foliage and richly colored flowers, but said to be difficult to grow. Rare in cultivation Closely related, if not identical, is E. grandi-florum, Andre, though figured with smaller heads of redder color. R.H. 1882:384.
(Hebeclinium macrophyl-lum, Lem., not DC. H. megalophyllum, Lem.). Half-shrub, robust: leaves opposite, round, more or less heart-shaped, very large, the lower sometimes more than a foot in diam., veiny: heads in large clusters (1-1 1/2 ft. broad); florets rose, the long hairlike styles conspicuous, bluish. S. Mex. R.H. 1866, p. 351. Gt. 16:548. - Fine showy species with rich foliage, but apparently rare and not recently in trade. Needs richly manured soil, much light, and frequent replanting.