PLANT OF THE WEEK

Dr. T. Ombrello - UCC Biology Department

COLEUS

Common names:     

Coleus, Flame Nettle, Painted Nettle, Painted Leaf, Poor Man’s Croton

Scientific name:    Coleus Blumei  (also known as Coleus x hybridus and most recently as Solenostemon scutellarioides)

Explanation of scientific name:

Coleus   - from the Greek “koleos”, meaning sheath.  The male portions of coleus flowers, the stamens, are fused into a tube or sheath.

Blumei   - named for Karl Ludwig Blume (1796-1862), a Dutch writer who wrote about plants from Java.

Note: It is very unlikely that the coleus plants in cultivation are all descendants of this one Javan species.  Instead, they are probably an assemblage of hybrids from many closely related species.  The scientific name Coleus x hybridus reflects this.  Taxonomists have now placed the cultivated coleus into a closely related genus, Solenostemon, with a species name of Solenostemon scutellarioides.

Coleus Blumei is just one of over 150 species of Coleus.  It is a large genus, with members naturally found from Africa to Asia, Australia, and the Pacific Islands.  As members of the Mint family of plants (Lamiaceae), coleuses are close relatives of peppermint, spearmint, salvia, basil, thyme, oregano, and Swedish ivy.  They all have distinctive stems that are square in cross section.  Coleuses are herbaceous perennials in their native habitat, with opposite leaves and small, blue to lilac flowers produced on terminal, spiked stalks.

What makes Coleus Blumei so interesting is the incredible foliage, with arrays of color combinations unmatched by other species. In your wildest imagination, come up with a color scheme for a leaf.  Odds are that somewhere there is a coleus to meet that description.  There are literally thousands of forms.

One of the most versatile plants in ornamental horticulture, coleus has a long-standing and well-deserved reputation as a plant just about anyone can grow.  Since it was first introduced to the horticultural world in 1825, it has always been popular, and was especially prized as a garden plant in the Victorian era. Coleus Blumei is one of only a few species with members that can thrive in sun or shade.  Provided with reasonable soil, fertilizer, and regularly watered, coleus will flourish in a garden during the summer or indoors on a windowsill or a greenhouse all year long.  They are notoriously susceptible to cold weather, and outdoors they will die with the first frost.

Coleuses are very easy to propagate.  Three or four inch long cuttings will readily produce roots, even in a glass of water.  Most mail order seed catalogs offer coleus seeds as mixtures.  As they germinate it is amazing to see how the complex genetics of this species allows for the expression of a seemingly endless variety of color combinations.

Besides their colors, coleuses exhibit different growth forms. Some grow several feet tall and are lanky, while others branch freely and are compact.  Some even trail and look great in window boxes and hanging baskets.  Just about all coleuses look better if regularly pinched.  By gently removing the terminal bud of each shoot when it reaches three or four inches in length, side branching is encouraged, producing more beautiful foliage.  Pinching will prevent flowering, but for many gardeners this is not a concern.  After all, the leaves are the show.