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.
(Greek for sheath, referring to the mona-delphous stamens). Labiatae. Common window-garden and greenhouse showy-leaved herbs, and a few less known species grown for the handsome flowers.
Herbs or small shrubs, annual or perennial, upright: leaves opposite, dentate or serrate, petioled or sessile: stem 4-angled: flowers mostly blue or lilac, in terminal spikelike racemes, small and middle-sized and usually bluish, the 5-toothed calyx deflexed in fruit; corolla bilabiate, the lower lobes longer and concave, and inclosing the essential organs; stamens 4, didynamous and declinate, the filaments united into a tube, the anther-cells confluent; ovary 4-parted, subtended by a gland-like disk, the style 2-lobed. - Probably 150 species, in the tropics of the eastern hemisphere, being especially abundant in Africa, E. India and adjacent isls. Some species produce tubers that are eaten in the same way as potatoes.
Fig. 1027. Coleus cutting.
The common coleuses are of the most easy culture. They root readily from short cuttings, cut either to a joint or in the middle of an internode (Fig. 1027). Few conservatory plants are more ready to root than this. They may be rooted at any time of the year when new wood is to be secured. Formerly coleuses were much used for bedding, but the introduction of better plants for this purpose has lessened their popularity. They require a long season; they are likely to burn in the hot summers of the interior country; they have a weedy habit. However, they withstand shearing and therefore are useful for carpet-bedding. The leading variety for this purpose is still the old Golden Bedder, whose golden yellow foliage is used as filling for fancy designs. - Coleus plants make excellent specimens for the window-garden and conservatory. Best results are secured when new plants are started from cuttings each spring. They also grow readily from seeds, many interesting leaf-forms and colors arising. The old plants become leggy, lose their leaves, and lack brightness of color.
They are very subject to mealy-bug. They are also liable to root-gall (the work of a nematode worm), as shown in Fig. 1028. When plants are thus affected, take cuttings and burn the old plants, and either bake or freeze the earth in which they grew.
A. Common garden coleus, with red, purple, yellow, green and variegated foliage.
(C. Verschaffeltii, Lem. C. scutel-larioldes variety Blumei, Miq.). This species, founded on cult, plants in Java, is probably to be regarded, as now understood, as an assemblage or combination of species. The horticultural forms are perhaps derived in part (as suggested by Briquet and by Koorders) from C. laciniatus, C. bicolor, and others; and perhaps they are to be considered also in connection with C. atropurpureus, Benth., of Malaysia, and its relatives. The entire garden material needs to be worked over in comparison with authentic native oriental specimens. Portraits of C. Blumei of botanical interest are: B.M. 4754. I.H. 27:3-7; 35: 46; 39:164. F.S. 22:228778. A soft perennial herb or sub-shrub, growing 2-3 ft. high, little branched: leaves ovate, narrowed or broad at base and long-acuminate, sharply and nearly regularly toothed, variously colored with yellow, dull red and purplish. An extreme form of this is variety Verschaffeltii, Lem., Fig. 1030, which is more robust and branchy, the leaves more brilliantly colored, acute but not acuminate, truncate or even cordate at base, and irregularly cut-dentate, with rounded teeth, giving the margin a crispy effect (I.H. 8:293). In some forms, the leaves are laciniate.
Fig. 1028. A coleus attacked by root-galls.
Fig. 1029. A good young coleus plant.
aa. Other species of Coleus, now and then in cultivation (Still other species may be expected to appear in the trade.) thyrsoideus, Baker. Tender shrub, 2-3 ft. high: stems pubescent: leaves cordate-acuminate, coarsely crenate, lower ones 7 in. long: flowers bright blue, in racemes which contain as many as 18 forking cymes with about 10 flowers in each. Cent. Africa B.M. 7672. - Considered to have much merit for cultivation, either under glass, or in the open far S. Winter.
Baker. Perennial herb, densely pubescent, 3 ft., much like the above in habit: stems angular, pale green turning to brown: leaves glandular, pungently aromatic, broadly ovate, acuminate, membranous, 2-3 in. long, deeply crenate, pubescent beneath but scantily so above: flowers dark blue (also described as light blue), in large erect terminal panicles. Cent. Africa B.M. 8024. - Winter.
Shrub, to 2 ft., pubescent, the branchlets slender: leaves petioled, ovate, acute, 2-3 in. long, crenate, membranous, pale and finely pubescent beneath and green and nearly glabrous above: flowers small, purple with golden anthers, in a large graceful panicle. Cent. Africa - Winter.
Fig. 1030. Coleus Blumei variety Verschaffeltii.
Soft perennial herb, white-hairy: leaves ovate, membranous, narrowed abruptly at base, crenate; petiole winged: flowers bright lilac (also described as ashy blue) in a long and lax racemose panicle, the whorls being about 8-flowered Nile Land. L. H. B.