Beautiful Bark

Auckland Park, in Bishop Auckland in County Durham, has a fine collection of venerable trees with beautiful bark patterns. 

Hawthorn Crataegus monogyna

Fluted trunk on an old hawthorn ....

.... with an elegant twist

Grey poplar Populus alba. The flat surfaces, between the fissures, are covered with diamond-shaped scars that look as though the bark has been hit with a pick, which is most evident on young trees like the one you can see by clicking here.

The old grey poplars have the most deeply fissured bark of any trees in the park ....

.... with splits so deep that they resemble crevasses 

Young silver birch bark peels away in thin layers (click here for a picture) but as it ages the bark splits and forms flaky plates ...... 

...... like this

Sweet chestnut Castanea sativa, with a bark pattern that resembles raised branching fibres ...

... with deep crevices where all manner of small invertebrates can spend the winter

A Tree-Spotter's Guide to Bark: Part 4

The success of London plane Planatus x hispanica as a street tree owes a lot to its propensity to slough off flakes of bark frequently, shedding pollutants along with it - and leaving an attractive abstract pattern of pastel coloured patches.

Marooned in a sea of of concrete and asphalt and assailed by exhaust fumes; it's a small miracle that plane trees like this not only survive but thrive in the urban jungle.

On a sunny day, it's pretty obvious how redwoods got their name. This is the giant sequoia Sequoiadendron giganteum, a species that was introduced into Britain in 1853. The bark is incredibly thick, soft and fibrous and, it is said, has been adopted as a roosting site by treecreepers that hollow out small depressions where they spend the night. Where did treecreepers roost before 1853, I wonder? The tree is sometimes known as Wellingtonia, named after the Duke of Wellington who died the year before it was introduced, but attempts to formalise this name as Wellingtonia gigantea - an act of imperialistic arrogance - upset the Americans. It was, after all, their tree so they countered with the name Washingtonia, to commemorate their national hero.... but there was already a palm species with the same name. Thankfully, it turned out that it was a cousin of the coast redwood Sequoia sempervirens and so could also be called Sequoia, circumventing any further taxonomic squabbling. It became Sequoiadendron in 1939, when detailed examination revealed that it was sufficiently distinct to be placed in a genus of its own. 

Horse chestnut Aesculus hippocastanum becomes flaky with age but isn't easily shed - so it often acquires a veneer of green algae on the northern, shady side of the trunk.

Elder Sambucus nigra rarely lives long enough to develop tree proportions but when it does the deeply fissured corky bark can be very attractive.

When common hawthorn Crataegus monogyna grows as a tree, rather than as a regularly cut hedgerow shrub, it tends to branch from low down from an early age and this produces a trunk that resembles vertical branches welded together - which is what they are, I suppose.

For more information on tree identification click here

A Tree-Spotter's Guide to Bark: Part 3

Few trees reveal the way in which patterns in bark are formed as clearly as the white poplar Populus alba. It's upper branches are clad in smooth pale grey bark, but mid-way down the tree it develops a series of splits, as though the tree has been attacked with a pick, where the bark begins to split under the strain of the swelling circumference of wood underneath. Here and there (towards the right of this photo, for example) you can see places where the splits begin to join up, to form fisssues until...

... near the base of a tree of medium age - perhaps 40 years old - the bole of the tree is covered in fissured bark, with those pick-marks barely visible on raised patches of smoother bark. As the trees age and approach the end of their lives....

...the fissures become deeper and the wonderfully textured character of the bark becomes apparent.

The bark of a mature sweet chestnut Castanea sativa bears this very distinctive pattern of branching and rejoining ridges. In many old trees the whole trunk appears to be twisted, so the pattern spirals up the trunk. 

Auckland Park in Bishop Auckland, County Durham, is home to several magnificient old sweet chestnuts with elephantine boles .....

... including this one which sits on a pediment of roots that seem to melt into the soil.

For more information in tree identification click here

A Tree-Spotter's Guide to Bark: Part 2

The grey-brown bark of alder Alnus glutinosa isn't particular distinctive - unlike the wood within. Freshly-felled alder wood turns a startling shade of red, although this quickly oxidises to a pinkish-brown. Understandably, the blood-like shade of the cut timber gave rise to many superstitions but didn't stop the coppicing of the tree for the production of high quality charcoal for gunpowder. Alder wood lasts exceptionally well if it's kept permanently wet or submerged - not surprising really, considering the tree's propensity for growing on riverbanks that frequently flood - and it was sometimes used for piles in bridge construction and also for the soles of clogs.

Wild cherry or gean Prunus avium bark is easily recognised by the long horizontal scars (lenticels) that run across the trunk. These are areas of porous bark that allow gas exchange for the living tissues below that generate new wood each year. Cherry bark also has a tendency to peel away in narrow strips around the circumference of the tree.

From a distance silver birch Betula pendula bark is dazzling white when it catches the sunlight, but a closer look reveals subtle shades of pink, orange and brown showing through from the bark tissues just below the surface. At this stage in the tree's life the birch bark peels away, sometimes in large sheets, as the diameter of the trunk expands (and so is ideal for birch-bark canoes) but as the tree ages....

-- the bark splits vertically, separating the white bark into flakey patches between deep fissures.

For more information on tree identification click here

A Tree-Spotter's Guide to Bark: Part 1

When you think about it, the bark of a tree is pretty remarkable. It's the tree's self-healing protective layer, defending the thin layer of living phloem cells inside, just below the surface, that conduct sugars up and down the stem and also protecting the living layer of cambial cells that produces new growth every year. It's waterproof, but it lets gases pass in and out and it's capable of expanding to keep pace with the growth of the tree, splitting and cracking as the tree ages in a pattern that's characteristic of each tree species. On one January day twenty-seven years ago the bark of this beech Fagus sylvatica was the canvas on which SP and CS carved a declaration of their undying affection; thankfully the wound healing properties of the bark meant that the tree still thrives, even though the union of SP and CS may or may not have endured.

The bark is a tree species' fingerprint. This is Scots pine Pinus sylvestris, with its irregular plates of warm red-brown bark that perfectly complement the deep, glossy green of its needles - especially when winter sunlight strikes the trunk.

The barks of pedunculate oak Quercus robur and of Durmast oak Q. petraea can't really be distinguished, so this could be either (although I happen to know that it was the latter because the acorns had no stalks). I think it may generally be the case that slow-growing trees like oak develop a rugged bark of ridges and fissures that are slowly added to with age, while fast growing species like sycamore and birch tend to develop more rugged splits or shed bark more readily. 

Sycamore Acer pseudoplatanus bark is smooth when the tree is young but soon develops into flattened, irregular plates that are slowly shed as the tree ages, flaking away to reveal a fresh layer below.

For more posts on tree ID click here