Coleus: New Light on a Shady Character

Photo credit: Dave Trinklein, University of Missouri Coleus 'Pineapple' is a gold-leaved cultivar shown here as part of a container planting. Coleus foliage tends to complement but not interfere with other container companions.

Mention the word "coleus" to most gardeners and mental images of a colorful denizen of shade comes to mind. Moreover, most gardeners today associate coleus with one of the several seed-propagated series of coleus grown for bedding plant pack sales in the spring. Coleus have long been prized for their colorful foliage which may combine shades of green, yellow, pink, red and maroon. New introductions of this popular annual have been selected for increased sun and heat tolerance, turning coleus into a "plant for all locations" in the annual garden.

Photo credit: Dave Trinklein, University of Missouri 'Gold Bedder' in the background is one of the sun-fast varieties.

The use of coleus as an ornamental herbaceous plant dates back to well before the Victorian Era. The species is native to Indonesia and parts of Africa. Because coleus has been cultivated as an ornamental for so many decades, its exact botanical origins are unknown, although Coleus blumei is most likely involved in its parentage. For that reason, the scientific name of this member of the Labiatae family is Coleus x hybridus. Equally confusing is the fact that plant taxonomists recently have reclassified coleus into the genus Solenostemon. It is said that Dutch traders carried several coleus species to Europe in the mid-1800s where plants breeders in various parts of the continent began to hybridize it. Each tried to create a new and more wildly variegated hybrid than his/her competitor; these new cultivars often commanded outrageous prices in the market. In the 1890s, both English and American gardeners adopted coleus with enthusiasm, both as a garden plant during the summer and a houseplant during the winter. Interest in this plant was so strong that the term "coleus craze" was used to describe the public’s enthusiasm for it during the Victorian Era.

Coleus to most gardeners is like a "comfort food" from childhood. It was often the first plant gardeners grew because of its ease but a plant they later forsook in favor of more ornate, "glamorous" species. If you have

Photo credit: Dave Trinklein, University of Missouri In an experiment reminiscent of the Victorian "coleus craze" this 2-year-old greenhouse coleus specimen was trained into a treelike standard. Unfortunately, the stem needs support because it is weak and not wind-hardy, so this plant can only be enjoyed indoors.

not tried coleus lately, you are in for a pleasant surprise for it has been improved greatly. The coleus of yesteryear had two glaring faults: 1) its inability to retain color in full sun, and 2) its tendency to produce unattractive racemes (compound flowers) during the long days of summer. The latter was actually favored by seed companies because collecting seed is easy in the summer, hence they were in no hurry to change the reproductive habits of coleus. In contrast, today’s coleus include cultivars that carry amazing sun tolerance along with a broad range of leaf colors, sizes, shapes and textures. Also, the newer cultivars are not long- day (summer blooming) plants and are vegetatively propagated. Their leaves remain the primary focal point throughout the summer with no unsightly flowers to remove.

Photo credit: Dave Trinklein, University of Missouri Seed propagated coleus of the Wizard series.

As with most annuals, well-drained soil is a must if coleus is to thrive in the garden. Poorly drained soils and/or excessive watering will result in stunted plants with "muddied" colors and discolored leaf margins. Pinching growing terminals of young plants will encourage dense, compact growth. A midsummer boost of fertilizer in the form of liquid fertilizer at half- strength can be helpful. When grown in properly prepared soil or in containers filled with a soilless medium, coleus is fairly resistant to serious disease or insect problems. An exception might be mealybug’s affinity for coleus as a food source. Coleus are multidimensional in their role in the garden bed or border. They make ideal companion plants for larger species and help to "fill in" vacant space under taller plants such as dahlia. Or, they can be used for creating effective color schemes by themselves or planted with other species of annuals. Because of the multicolored nature of their leaves, it is hard to find two coleus cultivars that do not go well together.

There are several hundred names cultivars of coleus, about forty of which are sun-fast. There probably is considerable duplication of names for some of these cultivars, according to the region of their use. ‘Red Ruffles’ is an exciting new red-leafed cultivar that has received much acclaim. ‘Alabama Sunset’, ‘Pineapple’, ‘Golden Bedder’, ‘Solar Flare’, ‘Confetti’, ‘Freckles’ and ‘Japanese Giant’ represent a brief listing of other favorites. Two series of sun-fast coleus that deserve mention are the Sun Goddess^TM series of vegetatively propagated coleus (only the name is trademarked, the plants are not plant patented) and the Stained Glassworks^TM series (PPAF in most cases). For a sampling of the types of coleus now available, one might wish to visit http://www.glasshouseworks.com on the web.

Dave Trinklein, Extension Floriculture, UMC