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We often think of trees as being at their most beautiful when clothed in a dense canopy of fresh leaves, and festooned with flowers. Many, however, have much to offer during the winter months by way of stem, branch colour and texture.
In their naked state, denude of leaves, the skeletal forms of trees can make a dramatic contrast to a stormy winter sky, appearing as dark figures silhouetted on the horizon. When bedecked with a haw frost, the drooping limbs of the native birch, Betula pendula, take on an enchanting, other-worldly appearance to bring another element to the winter landscape.
Closer observation of birch trees reveals an array of stem and branch effect, with a bewildering range of colours and textures evident. The Himalayan birch, Betula utilis, in its various forms, has peeling bark from pure white to brown, while Betula utilis ‘Sichuan Red’ has a smooth, dark brown bark, overlain with orange and red. In contrast, the stems and branches of the river birch (Betula nigra) are covered in curling, exfoliating brown bark.
The cherries are not to be outdone on the winter interest front, with the Tibetan cherry, Prunus serrula, having glossy, mahogany bark which demands great admiration. The maples too want a piece of the winter action, with several having distinctive bark to add another dimension to the garden. Acer griseum, the paperbark maple, has cinnamon-coloured bark, which curls with age, but which creates a dramatic effect. It is no coincidence that A. capillipes and A. grosser are often referred to as snakebark maples, having brown and green bark with vertical markings. One of the more imposing trees to provide winter interest is the Persian ironwood, Parrotia persica, whose flaky, self-grafting stems produce an intricate network of interwoven branches to create a broad canopy.
The more familiar native oak, Quercus robur, is also worthy of a mention. It has a rugged, branching frame and serves as a distinctive landmark, but how many of us have paused to admire its grey, fissured bark? The bark of a tree can provide one of the identifying features, but it is those with highly ornamental bark which are most desired by the gardener.
Finally, coniferous species also have their winter appeal. The single, vertical stems of Pinus nigra ssp. laricio, or the Corsican pine, are armoured with thick, scaly plates of bark whose grey, pink and orange hues are highlighted when lit by low winter sunlight. Equally dramatic in winter sunlight are the deciduous conifers, Metasequoia glyptostroboides (dawn redwood), and Taxodium distichum (swamp cypress). Each of these has fibrous, russet-coloured bark. Elegant as these are, neither can compete in scale with the giant redwood, Sequoiadendron giganteum, which dominates the landscape, and whose spongy, reddish-brown bark provides a protective insulation from forest fires. The lacebark pine, Pinus bungeana, provides another source of winter stem interest, displaying a smooth bark with patches of grey, brown and olive-green colouring, which sheds in small platelets to reveal younger bark beneath.
All these species add dimension to the winter garden, with their architectural form, and their textured and coloured bark. Some species, such as the Tibetan cherry, can be accommodated in a relatively small garden, but if you really wish to compare form and stem effect, a range can be admired here at the Botanic Garden.
Sally Pettit, Head of Horticulture, Botanic Garden