In the arboretum at Bryan's Ground in Herefordshire, I spotted a plant that I never thought I would get excited about. It was a smoke bush, which I had always thought of as a rather lowly background shrub, but this particular specimen, with its semi-translucent, coppery leaves, looked wonderful in its naturalistic setting with cow parsley growing underneath.
I discovered afterwards it was Cotinus 'Grace', and its late-spring leaves caught the light beautifully, unadulterated by the fuzz of smoke-like flowers that appear later on in the summer. Another garden in which I have admired cotinus is Great Dixter in East Sussex, where Christopher Lloyd planted several specimens in the meadow topiary garden, their loose forms contrasting beautifully with the clipped yew. Unlike some people, Christopher embraced the froth of summer flowers, calling them 'great dew-catchers'. In both these gardens, the cotinus had been set out in a natural-looking design tableau and I think that's why I was drawn to them. Equally they can be used in a more traditional mixed border - I have even seen them incorporated successfully into an Oudolf-style planting drift, which is perfectly possible if the plant is hard-pruned each year.
Smoke bushes are grown for the striking foliage, which ranges in colour from deepest purple to greeny-gold. The distinctive, clear-cut oval leaves emerge quite late in spring, already strong in colour, followed by the smoke-like plumes of flowers in summer. Then, as the flowers fade, the foliage comes back into play with strong autumn colour, so this is certainly a good value plant for a prolonged season of interest. Some people aren't enamoured by the flowers, but these can be kept to a minimum by pruning back in early spring, which will produce stronger, upright foliage growth at the expense of the flowers.
Cotinus isn't a huge genus, with only two species that grow wild in a large area from southern Europe to Asia and the US. C. coggygria is the European smoke bush, while the less frequently grown C. obovatus, is from the US. It has been grown in Britain since the mid seventeenth century and was mentioned in the famous sixteenth-century Herbal compiled by John Gerard (first published in 1597), where he referred to it as 'an excellent and most beautiful plant'. Then known as red sumac, Venetian sumac or Rhus cotinus, it was a highly prized shrub on the Continent, the leaves of which, Gerard wrote, were 'sold in the markets of Spain and Italy for great sums'. The leaves were used, among other things, to make black hair dye, and combined with honey and vinegar to make an ointment for gangrene.
Species and cultivars
The purple-leaved forms of cotinus are those that are grown most often and admired for their dusky, burnished foliage, which can add depth and contrast to a border for months on end. C. coggygria 'Royal Purple' is the most commonly grown cultivar, with deep purple leaves that turn deep crimson when backlit by the sun. In grey weather, however, the leaves can look leaden, so to make the most of them, they need to be planted in a scheme where they can be lifted by other plants around them. The lighter-coloured leaves and delicate pink flowers of Rosa glauca, for example, make an excellent companion, as do some of the ornamental grasses such as miscanthus or molinia, while in late summer, rudbeckias and asters shine out against its dark form. If left to its own devices, the plant will grow to about 5 metres, in a loose, multi-stemmed form; pruned back hard each winter, it will remain compact and easy to manage. 'Velvet Cloak' is very similar to 'Royal Purple', but with smaller leaves that have slightly more red in them. Anything with purple leaves needs plenty of light to thrive, so to ensure strong-growing plants, grow these plants in full sun.
The European species itself, C. coggygria, isn't grown as often as some of the other forms, because it has rather plain green leaves. But it can make an understated change to the others, and is topped with greeny-pink plumes in summer, followed by good colour in autumn, with the leaves turning shades of orange and red. The dwarf form 'Young Lady' has the same dark green leaves and, growing only a metre or so tall, makes a good choice for small spaces. It is particularly noted for its flowers, which cover the whole plant in a haze of smoky pink in summer. C. coggygria 'Golden Spirit' (sometimes known as 'Ancot') makes more of a statement with its golden-yellow leaves the colour of lime-green euphorbias when they emerge in spring. The flowers are greeny pink, and the leaves darken in the autumn to shades of orange.
The cotinus that I really want to try is a newly introduced cultivar called 'Old Fashioned'. Recommended by the Cotinus National Collection holder, Niki Thorp of Thorp Perrow Arboretum in Yorkshire, it has distinctive, large, bluey-green leaves contrasting with the reddish tints of freshly emerging leaves further up the stem - and in autumn these turn brilliant shades of deep pink and red.
Another rarely grown smoke bush is the American species, C. obovatus, also available from Larch Cottage. Larger than C. coggygria, it eventually forms a small tree up to about 6 metres tall, with reputedly the most intense autumn colour of all the cotinus, rivalling other autumn favourites such as acers and parottias. Related to this is 'Grace', the variety I came across at Bryan's Ground, which is a hybrid between the American species and the cultivar 'Velvet Cloak'. To my mind, this is the best all-round performer of the lot: coppery purple-green foliage in spring (crucially not too dark), followed by airy plumes of dusty pink flowers, and then amazing autumn colour, with the leaves turning translucent, veined crimson before dropping in October or November.
How to grow a smoke bush
Most cotinus prefer an open sunny position in the garden, particularly the purple-leaved forms, which need plenty of light for strong growth. Others may tolerate dappled shade, which may affect the colour strength of the foliage. Tolerant of a wide range of soil conditions, they are generally easy to grow, but do best in a reasonably moisture-retentive, but well-drained soil. If you have plenty of space and are growing them in a meadow setting, you can leave them to grow in their natural, multi-stemmed way,just giving them a light prune in late winter to remove any dead or diseased branches. If you want to grow them in a border, cut back the stems to within two or three buds of the base in early spring, followed by a thick mulch of well-rotted compost or manure around the base of the plant.