Cornus

Cornus are a group of 30-50 species of deciduous woody plants (both shrubs and trees) in the Cornaceae family. Most species grow with leaves which are opposite but a few do grow with alternate leaves. The flowers are small but are surrounded by bracts which are dramatic in themselves, in much the same way as a poinsettia plant. Cornus have been unfashionable up to recent times, mainly due to their use by councils in car park and roundabout planting schemes, but they are a useful plant for colour all year round, especially in winter.

Vibrantly contrasting Cornus stems in winter

 History   
 
The common name for Cornus 'Dogwood' is derived from the use of their slender stems for making 'dags' (daggers, skewers). The wood itself is prized for it's strength and hardness and was used in the making of shuttles for looms, tool handles, and wooden screws in fruit presses. Dogwoods have also the common name of 'Whipple-tree'. Geoffrey Chaucer uses the term in the Canterbury Tales. 

The term 'Dog-Tree' entered the English vocabulary by 1548 and by 1614 had become Dogwood. The latin name for Cornus came from the cornelian cherry, Cornus mas.

Cornus stolonifera 'White Gold'

Propagation

If the plant is a shrub species, generally, it can be propagated by hardwood cuttings from November to January. If it is a tree, then generally they can be grafted.

Cultivation

Cornus generally prefer moist soil and can tolerate sites which remain wet throughout the year. The species generally prefer full sun, but will growth in light shade.


Care

To get the best of their colour, the plants need to be cut back each spring (before the new growth on the buds has started for that year)  to around 5 - 7.5cm from the ground or to the previous year's stubs if you are pruning second, and any subsequent years after the plant was initially planted. If the plant has been recently planted, leave the plant to grow for a full season before pruning back.

Whilst this form of treatment is good for certain Cornus and Salix plants, others produce flowers, catkins or fruit on the previous year's growth so to get the best from them, they can be pruned by cutting approximately a third of the stems each year, removing the oldest and thickest ones first. Another option is to prune hard back every two or three years rather than every year.

The slow growing Cornus kesselringii, Cornus sanguinea and variegated Cornus alba 'Elegantissima' can be pruned by removing one stem each year or treating as above by pruning hard back every other year.

Cornus stolonifera 'Flaviramea' cut back in winter.

Pests and Diseases

Cornus are relatively pest and disease free. That said, some do suffer from Cornus anthracnose which is a fungal infection which gets to grips with the plant in cool, damp weather. Visible signs are spots which appear on the leaves in late spring and summer. As the infection take hold, parts of the plant die back and can cause the plant ultimately to die.

The infection can be stopped by pruning out all affected branches and burning them.

Further Info

Fruit of some of the species is edible but of little taste. That said, the berries of the subgenus Swida, whilst eaten by birds, are mildly toxic to humans. The stems are said to have been used by early pioneers who would remove the bark, then bite into the twig and then use it to 'brush' their teeth.

 Cornus sanguinea 'Midwinter Fire' stem

The National collection of Cornus is located at:

RHS Garden: Rosemoor
Torrington
Devon
EX38 8PH

Tel: 01805 624067
Fax: 01805 624717

Locate on Multimap here.