Coleus blumei

Plectranthus scutellarioides, commonly known as coleus, is a species of flowering plant in the family Lamiaceae (the mint or deadnettle family), native to southeast Asia through to Australia. Typically growing to 60–75 cm (24–30 in) tall and wide, it is a bushy, woody-based evergreen perennial, widely grown for the highly decorative variegated leaves found in cultivated varieties. Another common name is painted nettle, reflecting its relationship to deadnettles (Lamium species), which are in the same family. (True nettles and their close kin are in the family Urticaceae.) The synonyms Coleus blumei and Solenostemon scutellarioides are also widely used names for this species. Plectanthrus scutellarioides is an upright annual or short-lived perennial plant. It may be as much as 1 m (3 ft) tall, with well branched, more-or-less four-sided stems. Shorter, more trailing forms have sometimes been described as separate species, under names such as Coleus pumilus or Solenostemon pumilus, but are all now considered part of the very variable P. scutellarioides. The species is extremely variable in the colour and shape of the leaves. They are somewhat fleshy, varying in size from 1.5–10 cm (0.6–3.9 in) long by 1–6 cm (0.4–2.4 in) wide, generally ovate in shape, and borne on petioles (stalks) from 0.5–5 cm (0.2–2.0 in) long. The leaf margin is divided to a variable degree. Hairs are present on both sides of the leaf. The inflorescence is borne on the end of a stem and, like the leaves, is very variable in size; it may be up to 4 cm (1.6 in) long, with few or many flowers. The calyx is bell-shaped, initially only 1–2 mm (0.04–0.08 in) long, but lengthening to 5–7 mm (0.2–0.3 in) when in fruit. The bluish-purple petals are joined to form a typical two-lipped labiate flower, 8–10 mm (0.3–0.4 in) long. The stamens are joined for about half their length and are covered by the upper lip of the flower. The fruit is described as a 'nutlet', and is black, about 1 mm (0.04 in) long. The leaves of the wild species may be somewhat variegated, but this has been developed to an extreme degree in cultivated varieties, whose leaves may include one or more shades of green, white, cream, yellow, pink, red, maroon and dark purple. Green coloration is due to the amount of chlorophyll present in the chloroplasts in the leaves. Red, purple, pink, and orange colors are due to anthocyanins – water-soluble, flavonoid biosynthetic pigments, found in the foliage in addition to chlorophyll. The increase in anthocyanin production is accompanied by a decrease in chlorophyll production. The production of anthocyanins and chlorophyll is affected by light levels; the more light is present, the more anthocyanins are produced, with an inverse relationship to the production of chlorophyll. Anthocyanins are created inside the cell and facilitate photosynthesis in leaves that are exposed to very intense or prolonged sunlight by providing protection from damage caused by ultraviolet light. Some coleus cultivars over-produce anthocyanins and under-produce chlorophyll to the extent that optimal growth is prevented. The species was first described by Carl Linnaeus in 1763, as Ocimum scutellarioides. The genus Ocimum is best known for Ocimum basilicum, sweet basil. The specific epithet scutellarioides means 'resembling the genus Scutellaria' – a genus also in the Lamiaceae, whose name is derived from the Latin scutella, meaning a small dish or bowl. Genera and species related to Ocimum, placed in the tribe Ocimeae, have been the subject of considerable taxonomic confusion, and P. scutellarioides has been placed in several genera and been given multiple synonyms. Robert Brown transferred O. scutellarioides to the genus Plectranthus in 1810. George Bentham transferred it to the genus Coleus as Coleus scutellarioides in 1830, and in 1832 also described Coleus blumei, now regarded as just a variant of this species. It was transferred to Solenostemon by Leslie E. W. Codd in 1975. Placement in the genus Coleus, and the name Coleus blumei, led to the name 'coleus', still widely used by horticulturalists and gardeners, and now treated as a common name for this species. The synonym Solenostemon scutellarioides is also widely used. Within Plectranthus, molecular phylogenetic studies suggest that P. scutellarioides is most closely related to Plectranthus fredericii and some other species that are purely African in distribution.