Coleus is the common name for a group of evergreen, perennial plants of the genus Solenostemon from the Lamiaceae family. This increasingly popular and striking park-display plant is largely grown for its colourful variegated leaves, which range from light to dark green with a wide variety of markings in pink, red, yellow, purple, brown and cream. The plant is commonly grown as an annual and is used in summer bedding displays to provide colour and ground cover. It has a typical height and spread of 65cm.
Other common names include flame nettle and painted nettle because of the plant's ovate, toothed leaves, which are often hairy. The genus contains about 60 species and was introduced to Europe in the mid-19th century from the tropical and subtropical regions of Asia and Africa. Coleus is not frost-hardy and when planted outdoors needs to be in a sheltered position in full sun, which enhances its leaf colour.
Solenostemon scutellarioides - formerly known as Coleus blumei - and its cultivars are the most widely available of this genus in the UK with their square, semi-succulent stems and pointed, colourful, oval leaves. Listed simply as Solenostemon on the RHS Plant Finder database, there are many cultivars, including S. 'Wisley Tapestry' Award of Garden Merit (AGM), which is a popular addition to summer bedding schemes in parks due to its brightly coloured leaves in red, green and yellow. Other distinctive cultivars include S. 'Pineapple Beauty' AGM, which is very vigorous and quickly provides ground cover, with its long, maroon-splashed leaves of up to 8cm.
Coleus is grown commercially from cuttings and from seed, although those from cuttings tend to maintain the most dramatic varieties of colour, pattern and leaf shape. Cuttings can be taken any time between February and September, although a downside to this method of propagation is the need to keep plants at a minimum temperature of 15 degsC over the winter. Reliable seed varieties are also available, including the bright red S. 'Wizard Scarlet' and dark purple S. 'Pallisandra'. Seeds are sown in early spring but temperatures need to be around 21 degsC.
In cold and damp conditions, coleus can fall prey to downy mildew and Botrytis. The plants also become leggy with age and develop woody stems. This woodiness means, however, that they can be trained as standards and used as dot plants in bedding displays, although they are more commonly used as ground cover. While not grown for its flowers, the plant does flower throughout the year in largely insignificant whorls of tubular, two-lipped blue, white or purple blooms, which can be pinched out to encourage side shoots and create a more bushy plant.
WHAT THE SPECIALISTS SAY
Bruce Harnett, managing director, Kernock Park Plants, Cornwall:
"Coleus or Solenostemon species are generally bright with vibrant leaf colours. They are sturdy growers, although some of the seed varieties are less robust than those propagated by vegetative means. They are often used in landscaping as they stand out in a bedding scheme due to their bright foliage. Coleus is often used in Victorian-themed beds but can also be used in schemes with a contemporary twist.
"Our biggest seller is S. 'Combat', which has an interesting array of foliage colours - red, yellow, green. In the summer, coleus produces vibrant colours although it is not so good in the cooler months. There are thousands of varieties of coleus including lots of seed varieties, due to the large numbers of sports, and seeding programmes around the world.
"S. 'Walter Turner' Award of Garden Merit (AGM) is a stable variety to use in a planting scheme and is popular with landscapers while S. 'Peter Wonder' has an interesting frill around the leaf edge.
"We sell two types of coleus - big-leafed and finer-leafed varieties such as S. 'Fire Fingers' and S. 'Wisley Tapestry' AGM. S. 'Juliet Quartermain' is the most traditional and is well used for bedding."
Stuart Lowen, marketing manager, Ball Colegrave, Oxfordshire:
"The market for coleus has continued to grow, particularly with the increased interest in foliage plants. We have a number of new coleus being introduced. In particular, S. 'Chocolate Mint', which was introduced this year, was very popular with visitors at our open day last summer.
"The S. Kong series has been a very successful variety for growers and retailers generally as it was so unusual when it was introduced. It continues to be extremely popular because it quickly bulks up and gives a high-value large pot plant very quickly.
"I see the market for coleus continuing to grow, especially because the plant can be used in the sun. S. 'Watermelon' is a new variety for this year that will be very well received, possibly for parks where it can be used in exposed positions."
"One thing that comes out is the foliage has helped created huge interest in coleus as a genus. There is a lot of breeding work going on with vegetative and seed-raised plants getting larger to fill patio containers. It's a very fast plant to develop into a large pot.
"We want to put value back into bedding and coleus is a good plant to do this. From a £2 plant it very quickly bulks up into an £8 plant."
Martin Rodman, city gardens manager, City of London:
"We don't use coleus in permanent schemes as it is not robust enough for long-term planting. It is very prone to waterlogging and wind damage in the winter so is unsuitable for year-round planting schemes.
"I do, however, use them in seasonal bedding schemes. Granted, they do drink a lot, but in all other ways they are much better suited to the warmer summers - last year aside. They make an interesting change to the more common summer bedding plants such as Pelargonium and Begonia, and provide a really refreshing look to a garden.
"You can really give the effect of lightening a dark or dull area, particularly if you use bright varieties such as S. 'Wizard Pineapple' dotted with Nicotiana, and edge it with something like Chlorophytum."
- S. 'Chocolate Mint' is a new cultivar and has dark-brown leaves with a green edge. It reaches 30-35cm and can be grown in the shade or areas of filtered light.
- S. 'Combat' has dramatically coloured foliage of green, red and yellow, resembling army camouflage material. It prefers full sun and a well-drained soil, and can grow to a height of 50cm.
- S. 'Crimson Velvet' has vibrant crimson veins and velvet-textured leaves. It reaches a height of 50cm.
- S. 'Display' features orange leaves combined with purple veins and a yellow edging. It can grow to a height of 50cm.
- S. 'Fire Fingers' has deeply lobed, finger-like, purple leaves, edged with green. When grown in full sunlight, the leaves develop a flame of deep red. This cultivar is more compact than many others, reaching a height of 30cm, and is good for use as an edging plant.
- S. 'Juliet Quartermain' has distinctive nettle-like leaves and rich ruby foliage.
- S. Kong is a series comprising cultivars that display extremely large leaves and well-branched plants that grow to a height of 55cm. The plants are shade-loving and will fade in full sunlight.
- S. 'Peter Wonder' has very frilly, bright green leaves with creamy yellow veins and spiky pink edges. The whole leaf can develop a pink glow in full light conditions. It grows to a height of 50cm.
- S. 'Pineapple Beauty' Award of Garden Merit (AGM) is a vigorous cultivar that can quickly provide ground cover in a bedding scheme. It has deep maroon and yellow-green leaves of up to 8cm in length and can reach a height of 75cm.
- S. 'Royal Scot' AGM is a bushy cultivar with pointed, triangular, deeply toothed leaves of up to 6cm in length. The foliage is an orange-red colour with bright yellow edges. It grows to 45cm.
- S. 'Walter Turner' AGM has almost luminous foliage of green-yellow edges and maroon-red centres. It grows to a height of 50cm and needs a sunny position.
- S. 'Watermelon' has cherry-pink leaves and bright green margins. It is vigorous and can be grown in both the shade and in full sun. It reaches a height of 35cm with a spread of 30cm.
- S. 'Wisley Tapestry' AGM is a prostrate variety reaching 23cm with a spread of 45cm. It has very small leaves of 2cm in length and leaves of deep maroon in the centre with irregular red veining and deeply lobed margins of green and yellow.
- S. Wizard is a series characterised by dwarf, compact plants that reach 20-30cm. It flowers late, which adds to its landscaping value as it seeds late in the season. Popular varieties include 'Wizard Pineapple', with lime-green leaves and splashes of dark red and S. 'Wizard Sunset', with apricot leaves.