Coleus is a warm-climate plant grown mainly for its amazing velvety leaves, which glow with colour. In cooler climates it’s an indoor or heated conservatory plant, but in tropical and sub-tropical parts of Australia it is often mass planted in garden borders, where it looks spectacular.
What you need to know about coleus
Name: coleus (Plectranthus scutellarioides).
Height: up to 1m tall with a spread of about 60cm.
Foliage: oval, bright coloured, velvety and soft.
Climate: tropical to sub-tropical.
Soil: loamy, well-drained soil or premium potting mix.
Position: dappled shade—leaves will burn if placed in full sun; will tolerate full shade.
Flowering: spikes of small blue flowers typical of plectranthus; not a major feature.
Feeding: controlled-release fertiliser at planting, topped up with liquid feeds.
Watering: keep soil or potting mix moist but not wet; good drainage preferred.
Appearance and characteristics of coleus
Coleus is a perennial plant but is more often grown as an annual. It requires regular pinching out of the growth tips to keep it compact, as it is inclined to become “leggy”. Plants are generally around 80cm to 1m tall, and multi-branched.
There are many different varieties of coleus, each with its own pattern of colours and variegation. Some are symmetrical, while others are more random. The velvety texture of the leaves gives them a depth and glow that is quite stunning. Planted en masse, coleus create a magic carpet of colour.
Different varieties have patterns in shades of lime green, fluoro pink, crimson, burnt orange, brown, purple and yellow. The original coleus occurs naturally in South-East Asia, but it's now grown and admired worldwide. The colours in the leaves are caused by various pigments occurring naturally in the plant.
Coleus flowers are not the main attraction, and often the stems are removed before flowers open so they don’t detract from the foliage display. The flower spikes grow above the leaves and carry large numbers of small, usually blue flowers.
Coleus grown in pots can be “groomed” by regular pinching back of shoots to grow into compact, full plants where the leaves completely cover the branches.
How to plant and grow coleus
Coleus enjoys warm conditions—it will not do well in cold climates, or during winter in cool temperate to temperate regions where night temperatures can be very low. They are grown as outdoor plants in warm temperate to tropical areas, and glasshouse plants elsewhere.
Growing coleus in the garden
Coleus prefers a rich, loam soil improved by adding weathered animal manures and compost.
- Prepare the soil well before planting and include a six month controlled-release fertiliser to get plants off to a good start.
- Plant out seedlings in early spring and keep them well watered. Coleus does not tolerate dryness.
- Make sure excess water drains freely, otherwise your plant may develop root rots.
- As the plant develops, pinch out the growing tips to encourage branching and compact growth.
Growing coleus in pots
- Choose a pot that will be large enough to hold a well-developed plant.
- Always use a premium-quality potting mix—a terracotta and tub mix containing a 3–6 month controlled-release fertiliser, wetting agent and water storing crystals is ideal.
- As the plant grows, nip out the tips of shoots so side shoots develop.
Caring for coleus
Coleus does not tolerate dryness, so when the weather is hot and rainfall is scarce, water your plant regularly to keep the soil moist. Make sure excess water drains freely, otherwise plants may develop root rot.
For a coleus in a pot, keep the potting mix moist, but not wet, and allow excess water to drain away freely—don’t leave the pot standing in a saucer of water for more than 30 minutes.
Fertilising coleus in your garden
Use a water-soluble or liquid plant food every three to four weeks to keep plants healthy and growing strongly.
Coleus pests and diseases
Coleus is susceptible to downy mildew, which can cause leaves to develop a brown tinge and also to curl and twist. A general-purpose garden fungicide applied according to the directions on the label may help eradicate this. Good air circulation around plants is also important in controlling mildew. If plants are close together, you may need to remove a few to improve air movement.
In some areas, a virus disease spread by thrips may also attack plants. Known as necrotic spot virus, it makes its presence known by brown or yellow spots on leaves, stem discoloration and the veins of leaves turning brown. There is no cure—infected plants should be removed and binned to prevent spread by thrips to healthy plants.
How to propagate coleus
Coleus can be propagated by taking stem cuttings from established plants or by sowing seeds of selected varieties (packet seeds are available).
Growing coleus from cuttings
- To make a cutting, take a section of stem about 15cm long with a terminal growth tip.
- Cut just below a pair of leaves and strip off all but the top leaves and the shoot at the tip.
- Stand the cutting in a glass of water where it will quickly grow roots or insert it into a small pot of propagating mix.
If you like this then try
Impatiens: flowering annuals/perennials with brightly coloured flowers; thrives in warm climates in sun or shade
Croton: tropical to sub-tropical foliage plant with brightly coloured and patterned leaves; good for tall borders.
Hibiscus: brightly coloured flowering shrub perfect for tropical and sub-tropical gardens.
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