RHS GARDEN HARLOW CARR

Plant of the Month: January

Cornus alba 'Sibirica' Common name: Siberian dogwood Family: Cornaceae Vital statistics Height and spread: 2m (6ft 6in) high and wide Form: Vigorous deciduous shrub Soil: Any Aspect: Winter stem colour best in full sun Hardiness: Hardy throughout the British Isles

Image: Dorling Kindersley

Cornus alba 'Sibirica' can be found in the top beds of the main borders, opposite the Plant Centre. Situated along the top path leading from the gardens entrance to the Alpine houses, the bright crimson shoots stand out amongst the other dogwoods planted here including Cornus alba 'Kesselringii' with its black-purple stems and Cornus sanguinea 'Winter Beauty' with coloured stems from red through orange to yellow.

Cornus

The dogwoods, Cornus, comprise a small genus of around 45 species of mostly deciduous shrubs and small trees from northern temperate grasslands, woodlands and swamps. Cornus alba was introduced from Siberia in 1741 though it also grows in China.

The genus Cornus is so named as it is the Latin name for the cornelian cherry, Cornus mas, grown for its colourful yellow flowers produced in spring, followed by bright red, fleshy, edible fruit in late summer. It also produces a wonderful autumn display with the dark green leaves turning reddish purple.

Cornus alba 'Sibirica'

Cornus alba 'Sibirica' is a deciduous, upright-growing shrub with dark green leaves which bears clusters of small white flowers in spring and early summer, followed by small white berries. It is most commonly grown for its brilliant crimson stems, which are at their best on sunny winter days.
The stems are most brightly coloured on the previous summer's growth and gradually darken as spring approaches.
It is sometimes found under the name 'Westonbirt' or C. atrosanguinea.

Given the Award of Garden Merit by RHS Floral Committee B and described thus:
'Medium sized suckering deciduous shrub forming a thicket of slender red stems, becoming bright crimson in winter. Leaves ovate, flowers small, cream, in flat heads; berries bluish-white.'

Cultivation

Cornus alba will grow in any soil, moist or dry, but for the best winter stem colour a moist site in full sun is recommended.
Hard annual pruning produces the best display of colourful winter stems, but at the expense of flowering growth. However allow plants to grow unpruned for the first year after planting. Prune in early spring, before bud break, by cutting back all the stems to within 5cm (2in) of the ground, or within two buds of the previous year's growth. Neglected plants can be renovated by cutting out the old wood at the centre of the bush.

Cornus are rarely affected by pests and diseases, though some may suffer from Cornus anthracnose. This fungal infection is most prevalent in cool, damp weather, with infections showing as spots appearing on the leaves in late spring or early summer. As the infection develops patches of dieback may appear and in severe cases the plant may die. Cornus alba can be affected but only the weakest shoots tend to die while the rest of the plant remains healthy. To stop the infection spreading the affected branches should be pruned out and burnt.

Propagation

Softwood cuttings should be taken in summer or hardwood cuttings can be taken in autumn or early winter. Information about hardwood cuttings can be found by clicking here.

More information

Information about the National Collection of Cornus can be found by clicking here.

Further reading

Flanagan, M. 1998. January. The dogwood days of winter. The Garden. 123(1): 16-19.