<em>Coleus</em>: sowing, planting and care

Description and botany

Le Coleus or coliole is a perennial herbaceous plant native to tropical forests of Africa, the Americas and South‑East Asia, belonging to family Lamiaceae alongside nettle, sage and lavender.

Perennial in its native habitat, it is grown as an annual in our gardens or as a houseplant because of low hardiness — it cannot tolerate temperatures below 5 °C.

Genus Solenostemon, formerly Coleus, includes more than 150 species, cultivars and hybrids with very varied shapes and colours offering an impressive choice!

Hybrid coleus and cultivars most commonly sold in garden centres are derived mainly from species Solenostemon scutellarioides (syn. Coleus blumei) and are notable for particularly decorative foliage. They are often offered in series grouping varieties of different colours.

Fast‑growing, Coleus forms attractive bushy, erect, pyramidal, ramified habit that will reach 30 to 50 cm in height and almost as wide depending on variety.

Coleus – botanical illustration

Coleus is remarkable for sumptuous colours of its foliage. On quadrangular, fleshy, brittle stems unfold deciduous, opposite, ovate or heart‑shaped leaves, slightly dentate or deeply cut. They are sometimes so strongly veined and undulate that they appear puckered. Villous beneath and slightly velvety above, they measure 2 to 15 cm long and recall by appearance nettle or mint leaves. Depending on variety, leaves may be triangular, lobed, fringed or even tousled.

Elegant foliage of coleus never goes unnoticed. Ranging from striking to baroque or more discreetly coloured, leaves display solid or variegated colours, bicoloured or tricoloured patterns, sometimes surprising, eccentric to the point of loudness or rare in plant world. Colour palette is endless from absinthe green to zesty yellow, from rust to deep purplish‑red almost black (Coleus Palisandra or “painted nettle”) through Indian pink or creamy white.

With large soft, often variegated or marginate leaves splashed with lighter or darker tones combining several colours, some cultivars look painted and display often explosive contrasts (Coleus ‘Wizard Mixed’, Coleus hybrid ‘Rainbow’).

Coleus is grown for foliage rather than flowering. On this colourful vegetation, small bilabiate inflorescences gathered in small clusters appear from June to October at stem tips. Pink, mauve, blue or white, they are of little interest and are best removed to keep foliage vigorous.

Coleus is a cold‑sensitive perennial that fears frost, rarely tolerating temperatures below 5 °C, which is why it is cultivated as an annual to be sown or replanted each spring in garden beds, containers or pots. Coleus is also an excellent houseplant and can be kept indoors year‑round.

Very easy to grow, it prefers a sunny but not scorching position or partial shade to preserve vibrant colours and soil that is rich, light, deep, fresh but well drained.

Coleus is a valuable annual to bring contrast, colour and brightness to natural or wild gardens, modest in needs, perfect to create colourful mixed displays. Plant it in borders, along a path, in beds and flowerbeds, in rock gardens that are not too dry or in pots and containers.

Colour differences in leaves of some coleus are due to lack of chlorophyll between different zones.

The coleus canina, nicknamed “terreur des chats” belongs to a different genus (Plectranthus) and must not be confused with ornamental coleus: its foliage has an unpleasant odour acting as a repellent against dogs and cats.

Main species and varieties

Coleus, mainly from species Solenostemon scutellarioides (syn. Coleus blumei), are available in series as seeds such as the Wizard® series which includes hybrids in a range of colours, or as cultivars offered as plug plants such as Coleus ‘Black Prince’.

Most popular

Coleus blumei Palisandra Seeds - Solenostemon scutellaroides

Another recent horticultural creation distinguished by foliage of almost black colour. A rarity to adopt in garden or at home as an indoor plant.

• Height at maturity 60 cm

See the product sheet

Coleus Rainbow Mix Seeds

A magnificent selection with varied, variegated colours of purple, rust, garnet, absinthe-green and cream. Sow as focal point in a border but also to complement other plants and set them off.

• Flowering time July to November
• Height at maturity 50 cm

See the product sheet

Our favourites

Solenostemon Wizard Mixed

A recent horticultural creation offering magnificent, slightly velvety foliage in multiple colours. Very striking in borders, as an edging or in pots on the patio.

• Height at maturity 50 cm

See the product sheet

Coleus Black Prince

This Coleus owes its success to its magnificent, slightly velvety foliage of almost black colour. It tolerates sun very well, like all dark Coleus.

• Flowering time June to November
• Height at maturity 80 cm

See the product sheet

When and how to sow coleus seeds?

Sow coleus seeds from  January to March  under cover at a temperature of 20 to 25 °C .

Here’s how to proceed :

• On surface of good compost enriched with well-rotted compost, broadcast coleus seeds
• Do not cover seeds, they need light to germinate
• Water with a fine spray and keep moist until germination: germination will take 10 to 20 days
• Keep warm; prick out young plants into individual buckets as soon as they are sturdy enough to handle
• When young plants reach about 15 cm, pinch out the tip so they ramify
• Harden off plants gradually outdoors, but only place outside from late May to early June when temperature has warmed

Find our tips for successful sowing of annual seeds!

Planting coleus

Where to plant coleus?

Frost-tender, Coleus does not tolerate temperatures below -5 °C. It withers at first frosts! It is therefore cultivated as an annual in open ground in garden or in a pot on terrace or balcony. Bring pots indoors at first frosts into a lightly heated conservatory to keep them. It can also be grown as an indoor plant to keep year-round in a bright room out of direct sun; it will then be perennial and can be kept for several years.

Coleus likes well-drained soils that remain cool in summer, rich and fertile, even slightly acidic. It appreciates sunny positions where its colours will be enhanced, but prefers partial shade to blazing sun, which will preserve leaf colouring, especially in south of France.

Versatile, it is essential to adorn shady areas, flower a path border, the foreground of a flowerbed, a rockery that is not too dry, and to edge a summer flowerbed with elegance and colour. It creates eye-catching or more discreet colourful clumps in all naturalistic gardens and romantic gardens. Coleus is also ideal annual plant for pots and window boxes and a good conservatory plant.

When to plant coleus?

Planting of Coleus is carried out in spring from March to June depending on region, in all cases after last frosts when temperatures warm up.

How to plant coleus?

In open ground

Plant in May–June, when soil is warmed, spacing Coleus plug plants 25 to 30 cm apart and allow 4 to 5 plants per m2 for a splendid shimmering mass effect.

• Dig a hole 2 to 3 times larger than plug plant
• Add gravel or clay pebbles to bottom of hole
• Add a good handful of compost to each planting hole
• Place plug plant in centre of hole, and plant without burying collar
• Backfill, firm down
• Water

Enjoy our advice to succeed in planting annual flowers in plug plants

In pots

Plant only one Coleus per 15 cm pot. In a mixed planter, space plants 15 to 20 cm apart. All tips for planting window boxes and hanging baskets with annuals in plug plants are on our blog!

• Line base of container with gravel or clay pebbles
• Plant plug in a mixture of soil and leaf mould, amended with compost
• Fill and firm
• Water

Coleus care and maintenance

Coleus is one of those easy, low-maintenance annual plants provided soil remains cool and well drained in summer.

In pots as in open ground, throughout the growing season, Coleus needs regular waterings: water without waterlogging soil so it never dries out completely.

For potted coleus, add liquid fertiliser for flowering plants to irrigation water every fortnight: do not leave stagnant water in saucers.

Pinch back young plants regularly (remove shoot tips with thumb and forefinger) to encourage branching and keep compact clumps.

Remove flowers and flower buds as soon as they appear to prevent plant becoming exhausted prematurely and to maintain lush, colourful foliage.

In late autumn, lift coleus from ground and store pots in an unheated room or conservatory (10 °C) to bring them out again the following spring. During winter, keep in light and reduce waterings: root ball should dry out between waterings. Repot coleus at very start of spring each year.

Potential diseases and pests

Coleus is generally very resistant to disease. It is vulnerable to slugs that love its young foliage: follow our advice to fight their attacks!

If you notice aphids: spray water mixed with black soap or Marseille soap.

Coleus grown indoors are more vulnerable and are often prey to:

• mealybugs, visible from the cottony, sticky residue they leave on foliage: remove them with cotton wool soaked in 90% alcohol, then spray with rapeseed oil or a 5% black soap solution. Repeat regularly until they disappear.
• in a hot, too-dry atmosphere, red spider mites can develop, leaving spots on foliage: remove heavily infested parts immediately and spray non-calcareous water regularly on the foliage to maintain a consistently humid atmosphere around the pot. Spray nettle macerations.
• whiteflies are common on many indoor plants: they weaken coleus in case of infestation. Spray leaves with soapy water, optionally with a little vegetable oil added.

Find out more in our article: Coleus indoors: preventing and treating diseases and parasites.

Propagation: propagate coleus

Le coleus est une perennial frost-tender qui gagne à être pérennisé par propagation by cuttings au printemps ou en été. Le sowing est également possible au printemps et au chaud, comme vous pourrez le lire dans notre partie “when and how to sow coleus seeds”.

How to take cuttings of Coleus?

They are taken in spring or in June from non-flowering stems.

• Take stems 10 to 15 cm long
• Remove lower leaves and keep upper leaves
• Place these cuttings in a glass of water or in buckets filled with moist potting compost
• When roots develop after 2 to 3 weeks, pot up into 10 to 12 cm pots in a mixture of soil, potting compost and sand
• Keep frost-free in light at 15°C, watering regularly until next spring
• Pinch back young plants during winter
• In the following spring, plant the cuttings in open ground or in pots in May after frosts

Pairing coleus

Coleus is an indispensable plant in all colourful gardens, and even in shade gardens where its fascinating foliage brightens cooler corners. It is useful for creating colourful focal points, superb velvety clumps and subtle texture combinations.

One pot combination idea: Antirrhinum majus ‘Black Prince’, Begonia Summerwings ‘White Elegance’ and Coleus ‘Skyfire’

With its infinitely variable shades and fairly full habit, it adapts to every need and can be used alone or in small groups. It creates beautiful displays all through the growing season without relying on flowers.

To create strong visual impact, contrast colours in small touches. Cultivars with absinthe-green leaves marginate with cream will thrive at the feet of a golden bleeding heart or Dicentra spectabilis Goldheart®, a euphorbia, a Geum ‘Eos’ or the acid foliage of heucheras ‘Lime Rickey’, producing refreshing green gradients.

In red/black schemes, black-leaved coleus varieties pair well with plants bearing black-purple foliage such as certain hardy geraniums, heucheras, an ipomoea or lobelias.

For a graphic effect, create a contrast between the opulent foliage of coleus and the long, sword-like habit of phormiums, the tousled carex, and the dense, gracefully arched Uncinia rubra.

One border combination idea: Perovskia such as ‘Little Spire’, Stipa tenuifolia, Dahlia ‘Ivanetti’ and Coleus ‘Kingwood of Torch’ or a darker one such as ‘Black Prince’ would also work very well

It will elegantly edge a lush summer border alongside a mix of annual flowers such as love-in-a-mist, cosmos, a Linum grandiflorum ‘Rubrum’ or perennials with summer flowering such as delphiniums or lupins.

In a very colourful bed, pair it with the velvety flowers of Calibrachoa, a Convolvulus sabatius, ornamental sweet potato ipomoeas prized for their decorative foliage such as variety ‘Sweet Caroline‘.

In bold warm-toned compositions, it will sit alongside echinaceas, zinnias, an Amaranthus tricolour ‘Garden Select’, a fuchsia and large canna.

Black varieties such as ‘Black Prince’ add whimsy to a black garden and white garden, and combine in chic compositions with black flowers such as Iris ‘Black Knight’, black Arums, Alcea rosea ‘Nigra’, white foxgloves, hardy geraniums with purple foliage or an Ophiopogon ‘Hosoba Kokuryu’, set against Arundo donax ‘Variegata Versicolor’ and Acorus gramineus ‘Variegatus’ in the background.

Its very colourful character also finds a place among grasses such as Pennisetum and Miscanthus, which it will enliven.

It brings a graphic foliage note to window boxes and hanging baskets when mixed with impatiens, begonias, ornamental tobaccos or diascias.

Its beautiful leaves in warm tones (Coleus ‘Rainbow’) harmonise with certain bushes with coloured autumn foliage such as maples, barberries and deciduous euonymus.