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.
(old classical name). Zingiberaceae. Spiral Flag. Perennial thick-rooted tropical herbs, cultivated under glass for their flowing-limbed showy flowers, which are in terminal bracteate spikes.
Stems short or tall and leafy (plant rarely acaulescent), roots often tuberous: flowers golden yellow, red, saffron-colored or white; corolla tubular, cleft, not showy; 1 staminodium, enlarged and bell-shaped, usually with a crispy limb, and forming the showy part of the flower (called the lip), cleft down the back; ovary 3-loculed; filaments petaloid. - About 100 species, widely distributed in the tropics. More or less fleshy plants, prized in warm-houses, and grown in the open in S. Fla. and other warm regions. Monogr. by Schumann in Engler's Pflanzenreich hft. 20 (1904).
This interesting genus of tropical herbs thrives in any rich moist soil, but luxuriates in that of a gravelly or sandy character, when under partial shade. The plants are readily propagated by cutting the canes, or stalks, into short pieces of an inch or two in length, and planting in sifted peat, or fine moss and sand, covering but lightly. The roots may also be divided, but this is a slow means of propagation.
Specimen plants require rather high temperature to bring out the rich colors of the leaves, which in some species are prettily marked with a purplish tint, and are usually arranged spirally on the ascending stem. This gives rise to the name "spiral flag." (E. N. Reasoner.)
Smith. Somewhat woody at base, 4-10 ft., stout, erect: leaves oblong or oblanceolate, acuminate, nearly 1 ft. long, silky beneath: bracts red: flower large. with a flowing white limb and yellowish center, 3-4 in. across, not lasting. E. Indies. I.H. 43:56. Gn. 47:166.
N. E. Br. One to 2 ft.: leaves oblong or elliptic-lanceolate, 4-6 in. long: bracts not colored nor conspicuous: flowers clustered, orange-red. Brazil. I.H. 31:511. B.M. 6821. J.H. III. 28:11.
Few species of Costus are offered in this country, but others may occur in special collections. - C. Friedrichsenii, Petersen. 6 ft. or more: leaves sessile, lanceolate, acuminate, 1 1/2 ft. or less long: flowers very large, bright yellow in thick terminal spikes. Gt. 52:15-21. Cent. Amer.(?). - C. micranthus, Gagnep. 5-6 ft.: leaves spirally placed, lanceolate: flowers very small with red tube and orange-red yellow-tipped lobes, the lip tubular and purple, in cone-like spikes 3 in. long. Martinique. - C. musaicus, Hort. Leaves obliquely lanceolate, 4-5 in. long, dark green, marked and tessellated with silvery gray. W. Africa - C. zebrinus is very likely the same as last. L.H.B.