The dogwoods, Cornus, comprise a small genus of around 65 species of mostly deciduous shrubs and small trees from northern temperate grasslands, woodlands and swamps.
Cornus are extensively grown for a wide range of ornamental effects. Dogwoods such as Cornus alba and C. stolonifera are prized for their brilliant autumn foliage, handsome fruits and outstanding winter beauty provided by colourful stems which range in colour from yellow, crimson and almost black-purple.
The flowering dogwoods such as C. florida, C. kousa and C. nuttallii are also grown for their stunning autumn colour but it is their large white or pink bracts produced in early summer for which the group is most celebrated.
Cornus kousa var. chinensis
Introduced in 1907 from China, as the name suggests, Cornus kousa var. chinensis differs from typical C. kousa in its taller, more open habit, usually forming a small tree.
Cornus kousa var. chinensis reaches up to 7m (23ft) tall with a trunk of flaky bark and dark green leaves which turn a deep crimson-purple in autumn. In early summer green flowers are borne in inflorescences up to 1cm across. These are surrounded by four large tapered bracts, 5cm (2in) long, which open creamy white and then turn white before eventually fading to red-pink.
The flowers are followed by deep crimson, strawberry-like fruits.
Cornus kousa var. chinensis should be grown as a specimen tree in a fertile, humus-rich, neutral to acid soil in a location in full sun or partial shade. It is not recommended for poor, shallow, chalk soils.
Cornus kousa is best left to develop with a central-leader or as a branched-head standard with minimal intervention. Gradually clear a short trunk when young by pruning in the autumn or spring and then keep pruning to an absolute minimum. Dead wood should be removed after flowering but care must be taken not to damage the twiggy flowering growth. Cornus kousa does not tolerate hard pruning.
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. To stop the infection spreading the affected branches should be pruned out and burnt.
Cornus kousa var. chinensis propagates well by seed which should be cold stratified when ripe and sown the following spring.