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

Description and botany

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

Perennial in native habitat, it is cultivated as an annual in gardens or as a houseplant because of low hardiness, as it does not 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 or cultivars most commonly sold in garden centres mainly derive from species Solenostemon scutellarioides (syn. Coleus blumei) and are characterised by particularly decorative foliage. They are often offered in series grouping varieties of different colours.

Fast-growing, Coleus develops attractive, bushy, erect tufts with a pyramidal habit and ramified stems that reach 30 to 50 cm in height and nearly as wide depending on variety.

Coleus – botanical illustration

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

Elegant foliage of coleus never goes unnoticed. Sometimes dazzling, baroque or more discreetly coloured, leaves display solid or variegated, bicoloured or tricoloured patterns, sometimes surprising and eccentric at verge of the garish, and rare in plant world. Colour palette is endless, ranging from absinthe green to zesty yellow, from rust to almost black purplish red (see Coleus Palisandra or “Painted Nettle”), through Indian pink or cream white.

With large soft-to-touch leaves, variegated, marginated or splashed with lighter or darker tones combining several colours, some cultivars look hand-painted, bearing often striking contrasts (Coleus ‘Wizard Mixed’, Coleus hybrid ‘Rainbow’).

Coleus is grown for foliage rather than flowering. On these colour-rich plants, small bilabiate inflorescences gathered in little clusters appear from June to October at stem tips. Pink, mauve, blue or white, they have little interest and are best removed to preserve vigorous foliage.

Coleus is a frost-tender perennial that rarely tolerates temperatures below 5 °C, which is why it is grown as an annual to be sown or replanted each spring in garden beds, borders or containers. Coleus is also an excellent houseplant that can be kept indoors year-round.

Very easy to grow, it favours sunny but not scorching exposure or partial shade to preserve vivid colours and a rich, light, deep, cool but well-drained soil.

Coleus is a valuable annual for bringing contrast, colour and brightness to all natural or wild gardens, unpretentious, ideal for creating colourful mixed displays. Plant in bed edges, along a path, in borders and flowerbeds, in rock gardens that are not too dry or in pots and planters.

Colour disparities in leaves of some coleus result from lack of chlorophyll between different zones.

Coleus canina, nicknamed “terror of cats”, belongs to a different genus (Plectranthus) and must not be confused with ornamental coleus: its foliage has an unpleasant smell that acts as a repellent against dogs and cats.

Main species and varieties

Coleus, derived mainly from species Solenostemon scutellarioides (syn. Coleus blumei), are available in series sold as seeds such as Wizard® series which includes hybrids in various 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 notable for its almost black foliage. A rarity to adopt in the garden or 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 a focal point in a border or as a companion to other plants to showcase them.

• 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 beds, at the front of borders or in a pot 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 an 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:

• Sow coleus seeds by broadcasting on surface of good potting soil enriched with well-rotted compost
• 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 in warmth and 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 become ramified
• Acclimatise plants gradually to outdoors but only place outside from late May to early June once temperature has warmed

Find our tips to succeed with sowing annual seeds!

Planting Coleus

Where to plant Coleus?

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

Coleus likes well‑drained soil that remains cool in summer, rich and fertile, even slightly acidic. It enjoys sunny positions where its colours will be enhanced, but prefers partial shade to scorching sun, which will preserve its leaf colouring, especially in southern France.

Versatile, it is indispensable for dressing shady spots, flowering a path border, the front of a flowerbed, a rockery that is not too dry, and for festooning a summer bedding scheme with elegance and colour. It creates showy or more discreet colorful clumps, in all naturalistic gardens or romantic gardens. Coleus is also the ideal annual for pots and window boxes and a good conservatory plant.

When to plant Coleus?

Planting of Coleus is done in spring from March to June depending on region, in any case after last frosts when temperatures warm up.

How to plant Coleus?

In open ground

Set out in May–June, when soil has warmed, spacing plug plants of Coleus 25 to 30 cm apart and allow 4 to 5 plants per m2 for a beautiful shimmering mass effect.

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

Find our tips to successfully plant annuals in plug plants

In a pot

Plant only one Coleus per 15 cm pot. For mixed containers, space plants 15 to 20 cm apart. All tips on how to plant window boxes and hanging baskets with annuals in plug plants are on our blog!

• Line bottom of container with gravel or clay pebbles
• Plant plug into a mixture of soil and leaf‑mould, with added compost
• Fill in and firm down
• Water

Caring for and treating coleus

Coleus Coleus is one of those easy, undemanding annual plants provided soil remains fresh and well drained in summer.

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

For coleus in pots, every fortnight add liquid fertiliser to the watering water for flowering plants: do not leave standing water in saucers.

Pinch back young plants regularly (remove tip of shoots with thumb and forefinger) to encourage their branching and keep clumps compact.

Remove flowers and flower buds as soon as they appear to avoid prematurely exhausting plant and to maintain lush, colourful foliage.

At end of autumn, lift coleus from open ground and store pots in a frost-free room or conservatory (10 °C) to bring out again next spring. During winter, keep in light and reduce waterings: rootball should dry out between waterings. Every year at very start of spring, repot coleus.

Possible diseases and pests

Coleus is generally very disease-resistant. It is vulnerable to slugs, which love its young foliage: follow our advice on combating their attacks!

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

Indoor-grown coleus are more vulnerable and are often prey to:

• mealybugs, visible from the cottony, sticky residues they leave on foliage: remove them with cotton wool soaked in 90% alcohol, then spray rapeseed oil or a 5% solution of black soap. Repeat regularly until they disappear.
• in a hot, overly dry atmosphere, red spider mites develop, leaving spots on foliage: cut away heavily infested parts immediately and spray soft water regularly on the foliage to maintain a consistently humid atmosphere around the pot. Apply nettle infusions.
• 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 parasitic pests.

Propagation: propagate coleus

Coleus is a frost‑tender perennial best preserved by propagation by cuttings in spring or summer. Sowing is also possible in spring under warm conditions, as you can read in our section “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 bright light at 15°C, watering regularly until following spring
• Pinch young plants during winter
• Following spring, plant cuttings outdoors or in pots in May after frosts

Pairing coleus

Coleus is an essential plant in all colourful gardens, even shade gardens where its fascinating foliage lights up cooler spots. It is useful to create colourful focal points, superb velvety clumps and subtle texture combinations.

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

With its endlessly variable colours and fairly substantial habit, it suits every desire and can be used alone or in small groupings. It creates beautiful scenes throughout the growing season without relying on flowering.

To create a strong visual impact, contrast colours in small touches. Cultivars with absinthe-green foliage marginate with cream will thrive at the foot of a golden Cœur de Marie or Dicentra spectabilis Goldheart®, an euphorbia, a Geum ‘Eos‘ or alongside the acid foliage of heucheras ‘Lime Rickey‘ in refreshing green gradations.

In red/black variations, black-leaved coleus varieties will sit alongside plants with blackish-purple foliage such as certain hardy geraniums, heucheras, a morning glory or lobelias.

For a graphic use, create opposition between the opulent foliage of coleus and the long, sharp leaves of phormiums, the tousled carex, dense and gracefully arched Uncinia rubra.

A planting combination idea for beds: Perovskia such as ‘Little Spire’, Stipa tenuifolia, pompon dahlia ‘Ivanetti’ and Coleus ‘Kingwood of Torch’ or a darker one such as ‘Black Prince’ would also work very well

It will elegantly scallop the edge of a lush summer border alongside a mix of annual flowers such as nigellas, cosmos, a Linum grandiflorum ‘Rubrum’ or perennials with summer flowering like delphiniums or lupins.

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

In bold warm-toned compositions, it will neighbour echinaceas, zinnias, a tricolour Amaranthus ‘Garden Select’, a fuchsia, large cannas.

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

Its very colourful personality will also find a place among grasses such as Pennisetum and Miscanthus, which it will brighten.

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

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