What is a sorbus or rowan?
Sorbus are deciduous, hardy small- to medium-sized trees, occasionally shrubs, with ornamental flowering, fruiting and autumnal colour attributes. Commonly known as rowan (or mountain ash) and whitebeam.
Sorbus come Northern hemisphere, from temperate North America to temperate Asia and the rowan flowering season is March to May with fruiting from September to November. Size 1-20m high. Conditions needed to grow rowan or sorbus requires a moist but free-draining acid or alkaline soil, not heavy wet clay. Sorbus are hardy in the UK (to temperatures from -15ºC to -20ºC), with an RHS hardiness rating of H5 to H6, and are suitable for gardens in USDA zones 3a to 7b.
More about sorbus trees
Show me a garden that wouldn’t benefit from a sorbus, rowan or a whitebeam, and I’ll be very surprised. They’re readily available in nurseries, fairly easy to grow and they are hard-working trees, with a range of seasonal attributes including interesting leaf shape and colour, highly scented corymbs of white flowers, an array of differing fruit shapes and colours, and various forms of habit and shape. Add to that their value for wildlife and you have a winner.
The genus Sorbus, to which these trees belong, contains around 200 species and numerous cultivars of mainly small- to medium-sized trees growing up to 20m. They’re found growing across the northern hemisphere, from western Europe through Asia to the Himalayas and Japan, and in North America from Alaska to Arizona, and are at home in a variety of habitats, from lowland woodlands to high elevation limestone rocky outcrops in free-draining acid to alkaline soils. The red-fruiting American rowan, Sorbus americana grows in marshland and moist soils but will also happily grow on dry rocky hillsides. The genus has a complicated taxonomy but can easily be broken down into two main groups. The largest group is the subgenus Sorbus, commonly known as the rowan or mountain ash. These have pinnate leaves, terminal corymbs of flowers and small, round fruits called pomes, which contain two to ten soft seeds. They grow across the northern hemisphere from North America to temperate Asia. Sorbus aucuparia is our native rowan, with several good cultivars that have been selected for gardens, such as ‘Asplenifolia’ with deeply cut leaves, ‘Besissneri’, with a narrow upright habit, and ‘Sheerwater Seedling’, a popular upright tree with a perfect oval-shaped crown and large trusses of orange berries. Sorbus x kewensis is a hybrid of two subspecies of Sorbus aucuparia, and an outstanding fruiter.
How to care for sorbus
Most of the species Sorbus, such as Sorbus pallescens, Sorbus aria and Sorbus aucuparia, found in nurseries are grown from seed. All the named cultivars, however, are grafted. This is because there is no other way to replicate the authenticity of a particular cultivar that will not come true to form from seed. I plant my rowans and whitebeams as young as possible when they’re about 1-2m tall if grown from seed, and as a one-year old grafted maiden, just over 1m for the cultivars. Usually, these trees are container grown with young vigour and are generally quick to establish. With grafted specimens, the rootstocks will produce suckers that should be removed early in their growth by rubbing off the fresh green shoots with the thumb or, once they start to lignify, use secateurs before they get too woody. With seed-raised specimens, any shoots from the base can be retained and allowed to grow to form a multi-stemmed tree.
All Sorbus have a shallow root system and need a free-draining, acid to alkaline soil, but with some moisture, and will not tolerate their roots drying out. They prefer to be planted in cultivated ground, such as in a shrub or herbaceous border, where the roots zone is shaded, and they do not always approve of being planted as a single specimen in a lawn with fine turf where the tree roots cannot compete with compaction and constantly drying out. I prefer to plant in groups of three or five where space permits as they lend themselves to companionship and look more natural in that setting. All Sorbus are subject to infection from a variety of pests and diseases, particularly fire blight (Erwinia amylovora), and to avoid infection be sure to buy from nurseries that are free from the disease and ensure that all your pruning tools are cleaned and sterilised between pruning individual trees. When pruning Sorbus, always remove branches back to a strong lateral growth.
Where to buy and see sorbus and rowan trees
• Bluebell Arboretum and Nursery, Annwell Lane, Smisby, Ashby-de-la-Zouch, Leicestershire LE65 2TA. Tel 01530 413700,
• Burncoose Nurseries, Gwennap, Redruth, Cornwall TR16 6BJ. Tel 01209 860316, burncoose.co.uk
• Frank P Matthews, Berrington Court, Tenbury Wells, Worcestershire WR15 8TH. Tel 01584 812800, frankpmatthews.com
• Hillier Nurseries, Ampfield House, Ampfield, Romsey, Hampshire SO51 9PA. Tel 01794 368733, hillier.co.uk
• Landford Trees, Landford Lodge, Landford, Salisbury, Wiltshire SP5 2EH. Tel 01794 390808, landfordtrees.co.uk
•Dawyck Botanic Garden, Stobo, Peebles, Peeblesshire EH45 9JU. Tel 01721 760254, rbge.org.uk
• Ness Botanic Garden*, University of Liverpool, Neston Road, Little Neston, Ness, Cheshire CH64 4AY. Tel 0151 795 6300, liverpool.ac.uk/ness-gardens
• The Royal Botanic Gardens, Kew, Kew, Richmond, London TW9 3AE. Tel 020 8332 5655, kew.org
• The Yorkshire Arboretum, Castle Howard, York YO60 7BY. Tel 01653 648598. yorkshirearboretum.org
• Valley Gardens, The Crown Estate Windsor Great Park SL4 2HT. Tel 01753 860222, windsorgreatpark.co.uk
The best sorbus or rowan trees for your garden
© Nature photographers ltd/Alamy Stock Photo
The Swedish whitebeam is a medium-sized tree with a dense, rounded crown and dark, glossy green leaves that are grey-downy on the underside with white flowers and clusters of orange-red fruits. 15m. RHS H6.
Sorbus aff. filipes
A slow-growing rowan, often grown as a large shrub with fine, pinnate, dark-green leaves that turn a dark red-green in summer. Despite its size, it has large trusses of fruits that start a delicate shade of pink, turning white when mature. 3m.
Sorbus x kewensis
This small tree, a hybrid of two subspecies of Sorbus aucuparia, is an attractive rowan that has green pinnate leaves and offers highly scented flowers in spring. The bunches of bright-red autumn fruits are so abundant that they often weigh down its lateral branches. 6m.
Sorbus ulleungensis ‘Olympic Flame’
This small Sorbus tree has an extremely stiff and erect branching habit and stout buds with large green pinnate leaves. It has the best orange-red autumn colour of any rowan and large clusters of bright-red berries. 6m. AGM. RHS H6.
Known as Vilmorin’s rowan, this is a small, elegant, spreading tree that has beautiful, delicate, fine, fern-like pinnate leaves with lots of small leaflets. The hanging clusters of white flowers are followed by small, deep-crimson-pink fruits. 6m. AGM. RHS H6.
Sorbus ‘Chinese Lace’
A seedling of either Sorbus ‘Pagoda Red’ or a similar plant once grown at Kew, this ornamental rowan makes a small tree with deep-cut, lacy pinnate leaves turning a rich red-purple in autumn. The delicate white flowers produce red-orange fruits in autumn. 6m.
Sorbus hybrida ‘Gibbsii’
© Tim Gainey/Alamy Stock Photo
This is a vigorous whitebeam with an upright branching habit and a dense, columnar crown. The leaves are large, deep green and lobed. The abundant white flowers in spring give rise to very large green fruits that turn to a coral red. 12m. AGM. RHS H6.
Sorbus thibetica ‘John Mitchell’
A medium to large-sized upright whitebeam with a broad, rounded crown. The enormous leaves, which are up to 20cm round with a silvery underside, are the special attribute of this cultivar. The fruits are also large and russet-brown in bunches. 20m.
© time Gainey/Alamy Stock Photo
A small, flat-topped Chinese species that is often wider in spread than upright. Its doubly toothed leaves emerge bronze-tinted in early spring, before turning green. White flowers are borne in dense clusters, followed by persistent brown pear-shaped fruits. 5m.
© Tony Kirkham
The common whitebeam is a medium-sized tree with a compact, domed crown. Its wedge-shaped leaves are a shiny green above, with a silvery-white underside and turn a russet colour before they fall. Clusters of white flowers in spring are followed by scarlet-red fruits. 15m. RHS H6.
This Chinese whitebeam is an upright tree with narrow, linear leaves that are shiny green on the upper surface and silvery white on the underside. The cream flowers produce clusters of pear-shaped, white fruits from late summer that are tinged with pink. 9m.
© Claire Gainey/Alamy Stock Photo
Known as the Tibetan whitebeam, this is a variable, columnar tree with a round spreading crown. The new leaves emerge downy and a silvery-grey colour, turning green and become heavily ribbed. The fruits are large, round, amber-orange and speckled. 12m.
Tony Kirkham is head of Arboretum, Gardens and Horticulture at the Royal Botanic Gardens, Kew.