What was once your grandmother’s parlour plant is now the rage in outdoor plantings, both in pots and in garden beds. Best known for its vibrant leaves, coleus brings colour, texture and dimension to any garden. It can also be sweetly aromatic. Taxonomic authorities originally considered coleus part of the mint family and grouped it into different species or classified it as hybrids. But in 2006, they named all coleus plants Solenostemon scutellarioides. In 2012, that changed to Piectranthus scutellariodes. The plant has evolved in other ways, too. It’s been popular at various times over the last two centuries: as a houseplant in Victorian times and in the 1950s, and later on, as a trendy shade plant in summer gardens.
Today, people are admiring it once again. The National Garden Bureau, based in Illinois, designated 2015 year of the coleus. One of the reasons for the renewed popularity is because of its range of colours, sizes and uses. The plant comes in green, yellow, orange, pink, red, dark maroon, brown, cream and white. There is bound to be at least one cultivar that you admire. Leaves range from less than 2.5 cm in the “Thumbelina” plants and up to 20 cm in the “Kong” varieties. Its foliage can be solid or mixed in colour, smooth or ruffled, and comes in an array of leaf patterns that can feature splashes, flecks and veins of different colours.
Its structure can be upright or spreading. Coleuses are splendid in masses. The cultivar “Redhead” is a good example, which also excels in pots. The brighter colour combinations will bring interest to a shady corner. But new cultivars can grow in sun too; many of these require sun to bring out the best colour in the foliage. Check with your nursery to obtain the best coleus for sun or shade.
Perhaps best of all, coleus plants are not difficult to grow. One reason for their popularity in the past as houseplants is that plant enthusiasts could pinch off a few leaves (sometimes surreptitiously), place them in a glass of water on the window sill, and in two weeks have rooted cuttings they could plant. You can also start coleus easily from seed. If you want masses of plants, start them inside in the early spring so they will be ready to set outside after all danger of frost has passed. Warning: the seeds are tiny. Sprinkle them on a layer of pre-moistened, sterile potting soil in a shallow tray. Cover with a thin layer of fine soil, and protect the whole tray with a sheet of plastic to retain the moisture until the seeds sprout (about two weeks).
Then remove the plastic and keep the tray in a warm place, with bright (but not direct) sun until the seedlings are large enough to be planted into individual pots. Keep the soil evenly moist (water from below), and place the pots in a spot sheltered from wind and hot sun until they are ready to go into the ground. Once planted in the garden bed, keep the soil moist but not soggy. Here in Atlantic Canada, they will benefit from morning sun and some protection from the hottest part of the day. However, coleus can survive even afternoon sun as long as the soil doesn’t dry out. Mulch will help with this, but do not place the mulch near the stems or foliage. Composted manure will provide both fertilizer and mulch.
If you don’t want to start the plants inside, simply scatter the seeds on the ground once there is no fear of frost. You don’t have to wait for flowers to bloom, so you’ll have colour almost immediately. The difference between growing from cuttings or seeds is that a cutting will grow into the same type of plant from which you took the cutting. A package of seeds can contain a variety of colours and leaf patterns. If you want to use Coleus in containers, plant them in plastic pots; natural terra cotta will dry out too quickly. You may even want to add water crystals to store excess water that will be released when the soil begins to dry. The larger the pot, the less quickly it will dry out. The soil mix should contain lots of organic material and be light and airy.
For spectacular displays in pots, use a time-release fertilizer or a liquid fertilizer at half strength every two weeks (too much fertilizer will make the stalks grow too long). The plant also benefits from adding products that contain mycorrhizae to stimulate root growth. Coleus plants are tender annuals and will not survive a frost. Even frost-free nights below 10°C can damage or slow growth. Make sure temperatures remain around 15°C at night before planting, and they will flourish.
To promote the fullness that makes coleus plantings so lush, be sure to pinch back the ends of the branches once the plant is established. This forces side shoots to grow on each branch. Pinch off all flower spikes as soon as you notice them. If you plant coleus in a location with suitable sunlight, lack of wind and moist soil, it will be relatively pest and disease free. If there is a problem, it will probably be mealy bugs. Look for tufts of white fuzz on the leaves or stems and remove them using a cotton ball dipped in alcohol or insecticidal soap.
Coleus plants in your garden will add colour, texture, interest and even fragrance. They are also relatively inexpensive and easy to grow. You can’t ask for much more of a garden plant.