Coleus Can Create Color And Contrast

Last week we started taking a fresh look at one of the oldest newest plants in our ornamental gardens, the coleus. This week we’ll continue the review to see what’s really new and how to grow this garden gem. Leaf texture for coleus can be quite variable, with foliage that can include the features of being large, small, twisted, elongated, scalloped, lobed, finger-like, “duck’s foot” (webbed feet), etc. This overall foliage shape, affected by these other features, can be quite ornamental and add to the effect of the plant in combination with the coloration. Leaf texture for coleus should be a serious consideration when selecting and using coleus, as the visual contribution can be significant.

The wide range of coleus can be grouped into three basic plant forms, including upright, rounded and prostrate/trailing. Frequent snipping, pinching and trimming can help modify the form, although mature size will also vary depending on growing conditions and other factors. The trailing forms may also be considered semi-trailing and have value at the edge of a container or in a hanging basket. Trailing forms may also be effective as weaving groundcovers and will become a colorful, “living mulch” that not only adds interest but helps shade the soil for moisture retention and to discourage weeds.

Coleus has long been considered a shade plant, but, as I mentioned last week, they thrive in part shade and dappled shade and will languish in deep shade. In fact, their best leaf coloration is achieved with morning sun and some degree of afternoon shade. Many varieties do well in both shade and part sun, such as the ColorBlaze, Fairway, Superfine Rainbow, Main Street and the Kong series. Some varieties can take quite a bit of sun and are quite adaptable as long as they are not allowed to dry out. The color change can also be affected by temperature, available sunlight and soil fertility. These plants enjoy the heat and languish below 55 degrees, so don’t rush them. Cold, overly damp soils can result in leaf drop and may encourage disease problems. Plant coleus after any danger of frost has passed when soil temperatures have warmed sufficiently and evening temperatures are above 60 degrees. Avoid keeping the soil too wet or too dry, especially in pots and containers. Once established, the plants are not heavy feeders, and liquid or granular organics will be just fine.

To maintain plant form, pinch back most varieties every few weeks to prevent flower formation. This directs the plant to put energy into additional branching and foliage creation instead of flowering, thereby creating a fuller plant. When pinching off flowers, do so throughout the entire summer to create a full, lush plant. Pinch just above a set of leaves or branching junction for the best appearance (don’t leave a stub!).

Raising coleus from seeds is relatively easy. Seed strains offer uniformity and may include mixes or consistent coloration with identical plants. Seed packets can be quite affordable and a wide range of coleus varieties is available from seed vendors. Keeping in mind that coleus should not be planted out in the garden until all danger of frost is past, the timing of seed sowing should begin in March to early April. Sowing seeds in at least 3 inches of growing medium (maintain at 70 degrees) is recommended, and seeds should be sown on the surface, as they require light to germinate. Coleus seeds have a high germination rate, and you should have plenty of seedlings to transition to larger packs and containers.

Propagating coleus from either stem cuttings is quite easy. Snipping a small, 2-inch length of coleus and putting it in a rooting medium will start the process of new roots being developed. Select healthy, non-flowering cuttings with at least one or two leaf nodes, and you should also remove the growing tip when first placing the sample in your rooting medium. Rooting hormone can be helpful but isn’t necessary, and your new cuttings do not require fertilizer during establishment. Keep new cuttings moist (not soggy) and maintain high humidity with misting. Bright, indirect light (as in no sun) is recommended during the initial establishment of fresh cuttings. Keep cuttings warm and observe them frequently. Cuttings taken on a cloudy day will do best. This is one of the easiest plants to “root” from cuttings and a great way to learn the process. It can take as little as two weeks to have a well-rooted cutting.

Overwintering coleus plants and cuttings is certainly possible and a way to carry a particular plant from one year to another. Bringing coleus inside for overwintering as houseplants is one option, although temperatures near 70 degrees continue to be ideal. Rotate plants and pinch back as needed to maintain form. Consider grow lights as an option to provide adequate winter lighting conditions. Cuttings taken in the fall and processed as mentioned above are another option, but will require the same temperature, bright, indirect light and additional humidity by frequent misting.

When using these plants in the garden, remember that colorful coleus will have immediate and dramatic impact in the garden. Consider the merits of each variety as it relates to foliage color, leaf texture, plant form and, of course, what sort of neighboring plants will be involved. There should be some consideration to selection, landscape function, proper placement and proactive site preparation prior to planting. Solid-color coleus varieties such as Redhead and Lime Delight Premium Sun (both bred for the sun) can be very impactful and make a statement in the mixed border, while those with variable coloration may become “color echoes” for neighboring plants with similar (or contrasting) flower and/or foliage colors. The repetition of certain coleus colors and form can lend unity and harmony in the garden. While a solitary specimen can add a punch of color, consider the impact of mass planting as well. While coleus can do well as “role players,” they can also be elite members of your “leading cast.” Foliage with lighter coloration can provide illumination in shadier locations, while dark colors (for example, any coleus with Chocolate in its name) in the same setting will create depth and contrast. Consider coleus just one of many available tools in your gardening toolbox. Keep in mind that the wide range of leaf textures available, independent of color, should also be considered a potential ornamental asset—as should plant form.

All coleus varieties have excellent container potential if they are given an adequate volume of well-draining soil mix, reasonable nutrients and the proper light exposure to thrive. Avoid windy locations, as coleus can be prone to breakage in extreme winds. Slow-release fertilizers with a balanced mix of nutrients work well for your containers, although half-strength liquid fertilizer applied every two weeks over the growing season should be sufficient. Coleus do not show their best coloration if over-fertilized, so be conservative and consistent. Keep in mind that poor garden soils might necessitate an elevated container or raised bed to provide sufficient conditions for coleus to not just survive, but thrive! Container size is a factor, as the volume of soil should accommodate substantial rooting by coleus and any other plants that are involved in the design. Drainage is vital, so consider adding more drainage holes as needed. The container style, color and ultimate placement should also be considered in advance. Coleus-filled containers, if movable, allow for instant color, as they can be positioned as needed and used to add color, and to provide immediate interest and accent areas to the garden, deck or patio. Keep growing.