Coleus Fever Revived

The phrases “What goes around comes around” and “What’s old is new” apply to horticulture as they do to any other facet of life. Plants go in and out of favor, and it’s not uncommon to hear plants being referred to historically as “from your grandmother’s garden.” Such is the case with the remarkable coleus.It was the first plant I grew as a child more than a half century ago, and in Bush-Brown’s “America’s Garden Book,” with the original edition dating back to 1939, a reference to coleus says, “This is another plant which, along with geraniums and impatiens, used to be limited to baskets, boxes and Grandma’s windowsill. Plant breeders, however, have brought it out of these limitations so that today many cultivars are available that can be grown from seed with predictably good results.”

Well, there’s yet another coleus revival, and you may have noticed the abundance of coleus varieties at local garden centers. While old is yet again new, there are some updates and twists to this wonderful plant that you may not be aware of, with more to come.

On a trip to the national Botanic Garden in Washington back in the 1970s, I was astonished while walking around the garden on Maryland and Independence avenues, where there were coleus grown in ways that I had never seen before and haven’t seen since. Coleus, plants we see in 4-inch pots or as larger garden plants, were grown as standards, trees 4 and 5 feet tall with semi-woody stems and huge, 3-foot balls of foliage at the top. There were also huge, 3-foot pots with coleus rising from them in perfectly symmetrical cylinders 5 feet tall. Wire mesh had been put into the pots and lined with black plastic, with rooted coleus cuttings inserted into holes in the plastic, creating the appearance of a magnificently colored, 30-inch-diameter column of coleus that had the appearance of being one huge plant. There were also massive, 3-foot hanging baskets of coleus, and it was apparent that someone had learned the trick of letting these plants slightly wilt just once, as that causes them to pendulously hang—and the branches curve first downward, then back up to the sky.

So this week and next, I thought we’d take a look at this remarkable plant that’s incredibly easy to grow, has remarkable foliage textures, color and styles, and can be at home indoors and out in a variety of situations. You can grow some varieties from seed, but there are also some that are patented and can be only vegetatively grown. Always keep in mind, though, that we treat this plant as an annual, and if you find one that you like you’ll need to learn how to bring it from one year’s garden into the next.

Coleus is thought to have originated in Southeast Asia. While there is some debate as to when it arrived in Europe, a Dutch botanist, Karl Ludwig Blume, is credited with naming and introducing the plant in mid-19th-century England. This member of the mint family has the traditional square stems and opposite leaves. Considered a herbaceous perennial in its native range, coleus are used as annuals and once allowed to flower can begin to lose its vigor. Previously grouped into different species or classified as hybrids, coleus (formerly Coleus blumei and Coleus hybridus) were all placed under Solenostemon scutellarioides in 2006. As of 2012, taxonomic authorities consider the correct name for the coleus to be Plectranthus scutellarioides.

Victorian gardeners utilized coleus in vivid bedding designs, also called “carpet gardening.” These elaborate patterns were frequently designed to be viewed from above, and coleus were a common component in these planting schemes. New introductions generated excitement during this period of history and “coleus fever” was rampant for a time. Because coleus mutate frequently, sports and reversions were not uncommon and could result in a new variety of interest. Sports—a sport is a bud or part of a plant that has a different appearance from the rest of the parent plant—are seen as naturally occurring genetic mutations, while reversions—generally a hybrid plant that genetically reverts to its parent(s) in appearance or habit—represent the appearance of the plant at some point in its “genetic past.”

The popularity of coleus seemed to dwindle in the early 20th century and coleus didn’t see much of a resurgence of use until the mid 20th century, when uniform, seed-grown varieties became more popular and coleus also found some popularity as a houseplant.

In the 1980s, as more gardeners realized the full potential of this spectacular plant, the coleus boom was reinitiated. In the past two decades it has seen an amazing number of introductions in both seed and vegetative offerings. Many of the best selections have been preserved by coleus collectors and enthusiasts over the years, but there is no shortage of new varieties being selected and promoted each year.

While modern coleus breeding still focuses on new selections for the home gardener, featuring new color combinations and foliage characteristics, other features of consideration have become more prominent. There is certainly a focus on breeding and trialing for more sun tolerance, which will expand the use of coleus to the brighter portions of our gardens.

Although coleus is known primarily for its ability to be colorful in light to moderate shade, for sunny areas consider any of the Stained Glassworks varieties, the Wizard, Versa and Marquee series, or any variety with the word “sun” in its name. Breeding efforts also focus on delayed flowering, and more prolific branching, and there is certainly an emphasis on more compact and trailing forms, like Lava Rose, for containers and other tight spots in the garden beyond the traditional bedding scheme.

The primary ornamental feature of coleus is the foliage, which can be represented by green, pink, yellow, orange, red, dark maroon (near black), brown, cream and white. The range of shades for these colors and the possible combinations are seemingly limitless. This plethora of colors and combinations lends itself to the other common names for coleus of painted nettle or flame nettle. While some gardeners will leave the small flowers, it’s more common to pinch these off and back to a leaf node to encourage more energy into stem and foliage growth and not flowering. Coleus left to flower may lose vigor as the plant puts energy into seed production.

The variability in patterns, some subtle and some more dramatic, is truly amazing. While some selections will exhibit a solid color, other varieties may feature splashes, blotches, streaks, flecks, margins and veins. Color intensity may be affected by sunlight, heat sensitivity and other conditions. Bright sunlight can create a saturation of color, and the difference in appearance for most varieties in part shade versus full sun is noticeable. The term “sun coleus” refers to selections that have been observed to tolerate more direct sunlight, although moisture considerations become even more important in those locations. Darker cultivars tend to tolerate more sun, with the lighter varieties benefiting from some degree of shade to minimize leaf scorching. Morning sun and dappled afternoon shade tend to maintain consistent foliage coloration. The underside of the leaf may also feature an alternate color that can be a contributing factor visually as well. Optimal growing conditions are covered later in this article but consider that too little light will encourage a weak-stemmed, less vigorous plant without optimal coloration.

Next week, more about this plant, including growing it from seed, taking cuttings to keep your favorites, and a few of the rare issues you may have with this great plant. Keep growing.