By Melanie Mathieson
The Gardening Guru
The coleus plant has been available to gardeners for decades in a large variety of colours.
In the past, they were a favourite for planters and shade gardens because they are durable and easy to grow, and are best known for their bright colours and variety of foliage forms.
It is interesting to note that coleus is from the mint family, and is related to other plants such as ajuga, sage, thyme, basil, bee balm, lamb’s ears, lavender, lamium, and nettles.
In recent years, the coleus has had a bit of a makeover, resulting in some new hybridized varieties.
Today, the colour and foliage appeal seems to be endless with the addition of many new plants that now will thrive in a variety of light conditions, ranging from full sunlight to partial shade.
Coleus plants may be grown in the garden in full light, indirect light, or in partial shade. The intensity of light which the plant receives also will have a direct bearing on the intensity of the foliage colouring.
Some varieties may produce their best colour in light shade while others look best in bright lighting.
Make sure you check the care tag in the container before you buy in order to get the plants with the proper light requirements for your needs.
The lower-growing dwarf varieties (six-12 inches) will create a colourful border or you can use the taller (three-foot) types as a dramatic background planting.
Coleus also are quite striking when they are planted in a container or you can use coleus for mass plantings, a front or back border, or as a companion plant to something else.
The mixtures of foliage and colours with other perennials and annuals can be endless.
In our area, coleus is considered a tender annual as even the slightest frost will cause them to die.
Coleus like an evenly-moist soil which drains well. Make sure your plants that are in the bright sun receive adequate amounts of water (the first sign of wilt indicates they need to be watered).
Pinch the centre stems out when the plants are four-six inches tall to induce bushier growth, and be sure to pick off the flower spikes as they form.
Apply a good fertilizer in the same regime you have for your other annuals.
Expanding your coleus collection is quite easy as seeds are inexpensive, readily available, can be sprouted, and begin showing their first leaf colours in as little as two weeks.
Another advantage to growing coleus this way is that each packet of seeds will contain many different colours of plants, which you can choose your favourites to clone for the future by taking cuttings.
If your intent is to grow your coleus as a house plant, the seed may be sown indoors at any time of the year.
If the seedlings are destined for a garden location, they should be started indoors at least 10 weeks before your last expected frost so that the plants will be well-developed when it is time to plant them outdoors.
Be careful when you open the seed packet as coleus seeds are very small. Sow the seeds onto a layer of moistened sterile potting soil in a shallow tray, then cover with a thin layer of fine soil.
Keep the tray in a warm (65-75 degrees F) and bright place, but not in the full sun.
When the seedlings are large enough to handle easily, they should be thinned out and transplanted into individual pots. Because they are very fragile at this stage, seedlings always should always be held by a leaf, never by the stem.
When all danger of frost is past, the plants may be set out in the garden.
You also can propagate coleus by taking and rooting cuttings, which creates a clone of the initial plant.
Use a sharp, clean knife to cut the stem just below a leaf node. Remove the lowest leaves, dip the cut end into a rooting hormone, and insert it into some fresh, sterile potting soil.
They also will root quickly when set in moist sand or vermiculite, or even in a glass of room temperature tap water.
If you take cuttings in the fall, prior to a killing frost, you can grow your coleus as a house plant.
As older plants tend to become leggy and the foliage colour will begin to fade, in February or March take several cuttings from this plant and cultivate them to transplant into the garden for when the weather warms.
Propagation by cuttings is an effective way to renew an older plant as the “cloned” baby quickly will become the better plant.
Coleus make nice house plants as long as they receives sufficient light and food. Your coleus should be planted in a light, quick-draining commercial potting soil.
Place it where it will receive several hours of bright light (south window) each day, or provide artificial grow lighting for best leaf colour and fullness.
Coleus plants will adapt to a wide range of temperatures above 55 degrees F, but will grow best when they are kept between 70-85 degrees F.
Keep the soil evenly moist, but never soggy. Fertilize coleus with house plant fertilizer as per the instructions on the package.
Flower buds must be pinched off as soon as they develop to prevent the plant from producing seeds because once a coleus is allowed to go to seed, it has completed its life objective and usually will die.
Pinching also may be necessary to prevent leggy growth (any time that the tip growth is removed, the plant’s energy will be diverted to the lateral side growth, creating a much bushier plant).
Coleus are very durable so you can cut your plant back severely if needed.
So why don’t you try some coleus this season in your garden? I have had them in my containers at home and the office for the last two years, and they have performed wonderfully.