Coleus

Coleus: how do you recognise it?

Habit

A bushy plant 30–50 cm tall and about 40 cm wide, with square, fleshy stems.

Leaves

Opposite, oval to long, toothed or wavy; 5–15 cm long, in many colours and patterns.

Flowers

Small, pale blue to lilac flowers in spikes at the tips. They are usually pinched out.

Colour

Green, lime, yellow, orange, red, pink, purple and near-black, often combined.

Roots

Fine and shallow; they form quickly on cuttings, even in a glass of water.

Sowing: February–April · Plants: June · Pruning: May–September

Why grow it?

• Colourful leaves from June until autumn, without having to wait for flowers.
• Brings colour to partial and full shade, where few flowering annuals grow well.
• A huge choice of colours and leaf shapes, from finely toothed to broad and wavy.
• Very easy to root from cuttings: one plant becomes ten in a few weeks.
• Can come indoors as a houseplant in autumn and keep growing for years.

Coleus: where does it grow best?

• Light shade or partial shade; morning sun is fine, but strong midday sun can bleach or scorch the leaves.
• Humus-rich, free-draining soil: sand, loam or clay, acid to neutral. In a pot, ordinary potting compost and a drainage hole.
• Moist: the soil must not dry out, but should not stay wet either.
• A warm spot sheltered from wind. Allow 30–40 cm between plants.
• Indoors: a light spot by the window, out of strong midday sun, at room temperature.

Light

Partial shade and shade

Soil type

Sand, loam or clay

Acidity

Acid or neutral

Moisture

Normal

Size

0.5 m tall, 0.4 m wide

Hardiness

Frost tender: plant out after the last frost (mid-May)

Goes well with

• Busy Lizzie: A flowering partner for the same shady pots and beds.
• Begonia: Flowers all summer in partial shade and likes the same care.
• Ferns: Fresh, fine green foliage as a calm backdrop to the bright colours.
• Hosta: Large, calm leaves in the same partial shade.

Coleus: when and how to plant it?

Plant in June.

1. Sow indoors from February to April at 20–24 °C. Scatter the seed on the surface and do not cover it: it needs light to germinate, in 1–3 weeks.
2. Prick out the seedlings into individual pots and pinch them when they have three or four pairs of leaves.
3. Harden the plants off outdoors during the day in late May; only put them out when nights stay above 10 °C, usually in June.
4. Plant them at the same depth as in the pot, 30–40 cm apart, in soil enriched with a little compost.
5. Water straight away and lay a thin layer of mulch around the base.
6. In a pot or container: choose a pot with a hole, ordinary potting compost and a layer of gravel at the bottom.

Care

Watering

Keep the soil slightly moist. In dry spells the leaves droop; water at once and they will perk up again.

Feeding

From June to September, liquid feed for foliage plants at half strength every two to three weeks.

Pinching

Regularly pinch or snip out the stem tips, just above a pair of leaves: this makes the plant full and compact.

Flower spikes

Pinch out flower spikes as soon as they appear: flowering makes the plant leggy and the leaves smaller.

Indoors

As a houseplant: a light spot, room temperature, keep the compost slightly moist and do not feed in winter.

Tip: Grown for its colourful leaves: pinch out the flower spikes and the stem tips for a full plant. Only put it outdoors at the end of May, as it cannot stand cold.

Coleus: when to prune it?

Pruning months: May–September.

When: Pinch the stems regularly from May to September, and remove the flower spikes as soon as they appear.

How:

• Pinch or snip the tip of a stem just above a pair of leaves; two new shoots will grow there.
• Remove flower spikes with a little piece of stem as soon as you see them.
• Cut long, bare stems back to a few pairs of leaves above the ground; they soon reshoot.
• Use the removed tips as cuttings.

Caution: Wear gloves if you have sensitive skin, as the sap can irritate.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Cuttings

From May to September: take tips 5–10 cm long, remove the lower leaves and stand them in a glass of water or in moist cutting compost. They root in 1–2 weeks.

Seed

Sow indoors from February to April at 20–24 °C, without covering the seed. The seedlings vary in colour: pick out the best.

Coleus: how does it get through the winter?

Hardy to 8 °C: protect in harsh winters.

• Not hardy and sensitive to cold: it suffers below about 8 °C. Outdoors it dies in autumn.
• Bring potted plants indoors before nights drop below 10 °C, usually in September.
• Easier: take cuttings in August and overwinter them on a light windowsill at 15–20 °C.
• Indoors in winter: plenty of light, less water, no feeding, and pinch back long stems now and then.

Diseases and pests

• Mealybug: White, woolly tufts in the leaf axils, especially indoors. Wipe them off with a cotton bud and keep the plant apart; discard badly infested plants.
• Whitefly: Tiny white flies under the leaves. Hang up yellow sticky traps and rinse the leaves regularly.
• Slugs: Eat holes in the young leaves outdoors. Pick them off in the evening.
• Bleached or scorched leaves: Too much strong sun. Move the plant to light shade or a spot with morning sun only.
• Leaf drop and limp stems: A sign of cold or soil that is too wet. Move the plant somewhere warmer and let the soil dry a little between waterings.

Through the year

• January: Overwintered plants and cuttings on a light windowsill. Little water.
• February: Sow indoors at 20–24 °C, without covering the seed.
• March: Sow. Take cuttings from overwintered plants.
• April: Prick out and pot up the seedlings.
• May: Pinch. In late May, harden off outdoors during the day.
• June: Plant out once nights stay above 10 °C. Pinch.
• July: Pinch out flower spikes. Water and feed.
• August: Pinch. Take cuttings to overwinter.
• September: Bring potted plants or cuttings indoors.
• October: Outdoors, clear away dead plants. Indoors, give them a light spot.

Edible and useful

Not edible. Coleus is mildly poisonous: eating it causes vomiting and diarrhoea, and cats, dogs and horses are the most sensitive. It is not a herb: the colourful leaves are not for tea or salad, even though the plant belongs to the mint family, like mint and basil. Keep it out of reach of pets that chew plants and of small children, and wear gloves when pinching out and taking cuttings if you have sensitive skin, as the sap can irritate it. If any is swallowed, call a poison centre (in Belgium 070 245 245) or your doctor at once.

Did you know?

• Despite its Dutch name ‘siernetel’ (ornamental nettle), it is not related to the stinging nettle but to mint and sage: you can tell by the square stems.
• In the 19th century coleus was very fashionable in England as a bedding plant, and new colour forms were bred all the time.
• It has often changed its name: Coleus, Solenostemon and Plectranthus. Since 2019 it has been called Coleus again.