Most tree and shrub bark is brown, often smooth and sometimes gnarled – but a few plants have colourful bark that, in many cases, flakes away to reveal patches of different underlying colours. These plants are prized for garden winter interest.
The outer bark is what we see. It protects the tree from animals and the weather. It is constantly renewed from the inner bark (phloem), which carries food from the leaves to the rest of the tree. Phloem is short-lived, turning into outer bark, which is constantly added to or renewed. Replacement phloem is generated from the underlying cambium, which is the growing part of the tree.
Lenticels (pores) pierce bark so that air can get in to support the living tissues below the bark. Gardeners are sometimes alarmed to see bark splitting as trees grow, but this seldom leads to serious damage and there is, in any case, nothing that can be done.
It is uncertain why some woody plants use pigments to colour outer bark. Flower colours are known to be important in attracting pollinators, but coloured bark function is somewhat mysterious. Although most bark stays put, often becoming deeply textured, other bark naturally flakes along the corky layers as the tree grows, probably to dislodge harmful insects.
Tibetan cherry, Prunus serrula “Branklyn”, (8m height) is one of the finest trees for bark interest. It has copper-coloured, gleaming, peeling bark as well as white spring flowers and bright autumn colour. Its bark is best enjoyed close up, so plant next to a path that stays dry in winter. When accessible, the bark can also be stroked. Choose a site where winter sun will fall on the bark. Don’t pull peeling bark away, irresistible as it might be, in case you expose vulnerable living tissues. Gently washing stems to show off colour, however, will do no harm.
Other highly attractive barks that must be seen up close include birches such as Betula utilis subsp. albosinensis “Red Panda” (12m), with red bark that peels from an early age; Betula utilis subsp. utilis “Wakehurst Place Chocolate” (10m), peeling in shades of brown and paperbark maple; and Acer griseum (10m), with red flaking bark.
Bark interest acers also have good autumn colour. Younger plants don’t always show good bark, so if possible buy larger specimens, funds permitting.
Sinuous “snake-bark” is a charming feature of certain maples – green-and-white striated Acer davidii Viper (“Mindavi”) (10m) and Acer capillipes, with red-white striping, for example.
Shrubby Kolkwitzia amabilis (3m) – grown for its abundant spring flowers – also has brown peeling flaky bark for winter interest.
Another shrub, Euonymus alatus “Compactus” (1m), has characteristic corky wings on its shoots as well as red autumn colour and red fruits opening to reveal orange seeds.
Straddling the tree-shrub boundary, Acer palmatum “Sango-kaku” (pictured) has red-pink new stems and delicate summer foliage that yellows in autumn.
For a tree to be admired at a distance – as a lawn centrepiece, for example – white-stemmed birches are widely planted: Betula utilis subsp. jacquemontii “Doorenbos”, for example, or for orange bark peeling to white Betula “Fascination” (12m) is a good choice.
Multi-stemmed trees with bark interest cost more than single-stemmed examples, but suit small spaces such as front gardens or alongside taller trees.
Most bark-interest trees are deciduous, but the evergreen Arbutus × andrachnoides (6m) and Arbutus unedo (6m) have peeling red bark as well as long flowering season and strawberry-like fruits. Being slightly tender, they suit sheltered courtyards and coastal gardens.
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