Coleus
| Solenostemon subsp. var. | Coleus | |||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Solenostemon is a genus of perennial plants, native to tropical Africa, Asia, Australia, the East Indies, the Malay Archipelago, and the Philippines. They are commonly known as Coleus, a name which derives from an earlier classification under the genus name Coleus, which is currently treated as two: with species included in either the genus Solenostemon or in another genus, Plectranthus.
| Standard Cyclopedia of Horticulture |
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Coleus (Greek for sheath, referring to the monadelphous stamens). Labitae. 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: lvs. opposite, dentate or serrate, petioled or sessile: st. 4-angled: fls. mostly blue or lilac, in terminal spike like racemes, small and middle sized and usually bluish, the 5 toothed calyx deflexed in fr.; 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 Air., E. India and adjacent isls. Some species produce tubers that are eaten in the same way as potatoes. 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.
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| Standard Cyclopedia of Horticulture |
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Solenostemon (Greek, tube and thread, referring to the fact that the filaments are grown together, at their base, into a tube). Labiatae. Erect herbs allied to Coleus, probably similarly used: lvs. ovate, crenate, long-petioled: whorls of fls. laxly 6- to many-fld., arranged in long racemes or panicles: fls. small; calyx ovoid-campanulate, upper tooth ovate with decurrent edges, lateral small, lower oblong, as long as the upper; corolla-tube exserted, slender, dilated and oblique at the throat, the limb 2-lipped, upper shorter, lower long, oblong, slightly concave; stamens 4, the filaments united at their base into a tube; disk glandular: nutlets ovoid, smooth.—Eight species, W. Trop. Afr.; one also occurs in Brazil.
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Cultivation
Template:Nowrap the southeast Asian species Solenostemon scutellarioides have been selected for their colorful variegated leaves, typically with sharp contrast between the colors; the leaves may be green, pink, yellow, black (a very dark purple), maroon, and red (somewhat resembling the unrelated caladium). New cultivars with varieties of colors are constantly being made. The plants grow well in moist well-drained soil, and typically grow 0.5–1 m tall, though some may grow as tall as 2 meters. Coleus are typically grown as ornamental plants. They are heat-tolerant, but they do less well in full sun in subtropical areas than in the shade. In mild areas (no snow in winter), plants can usually be kept as perennials if well managed. In colder areas, they are often grown as annuals, since the plants are not hardy and become leggy with age (to encourage bushing in leggy plants, simply pinch back growing tips). In bright, hot areas, the colors of the plant are typically more intense in shaded areas than in full sun, and the plants will require less water there. Coleus also make low-maintenance houseplants. The plant's flowers grow on a stem above that stem's leaves, and tend to be purple and quite small in comparison to the leaves. The plant is not generally grown for its flowers, as it promotes stem elongation (remove to halt this).
Propagation
There are two ways to propagate Coleus. Seeds are inexpensive and easily obtainable. To germinate, simply sprinkle seeds on the surface soil and press down. Seeds need light to germinate, so avoid covering the seeds. To keep seeds moist, grow in a container and cover with plastic, or mist seeds daily (if starting seeds directly in the garden). Sprouts can show color in as little as two weeks. Alternatively, cuttings can be taken. Cuttings root readily in plain water, without the addition of rooting hormone (although it is still beneficial).
Pests and diseases
One disease that can affect coleus is downy mildew. This mildew appears on the leaves making the plant look dirty because it is brown in color. The organism is called Peronospora sp. and can also result in curled and twisted leaves. Sometimes symptoms are not found on leaves which make the disease harder to control.[1] Another disease is impatiens necrotic spot virus which causes brown or yellow spots on leaves, rings, black or brown stem discoloration, and brown leaf veins, ultimately resulting in plant death. The disease is spread by an insect called a thrips that carries the virus from an infected plant to an uninfected plant. It only takes a few of these insects to infect a whole greenhouse. [2]
Varieties
Species include:
- Solenostemon autranii (Briq.) J. K. Morton
- Solenostemon rotundifolius (Poiret) J.K. Morton
- Solenostemon scutellarioides (Linnaeus) Codd (syn. Coleus blumei)
- Solenostemon shirensis (Gürke) Codd
- Solenostemon pumilus
Gallery
photo 1
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References
