As stated in the previous post, bark is a mixture of living and dead cells.  Cork cells abound, especially in trees like the cork oak, where the cork may be regularly harvested.  This may be used for flooring, insulation and yes - corks for wine bottles. However, bark is a source of many things.  From early times, bark from trees like alder, buckthorn, oak, birch etc were used to make dyes for clothing.  Material from the inner bark of some trees (e.g. lime, willow, mulberry) was a source of fibres for clothing and cordage (string / yarn). Herbalists also found a use for the bark of certain trees.  Infusions of willow were used to treat fevers, the ‘ague’, rheumatic aches and pain.  It contains salicin, which the body converts to salicylic acid, an early 'form' of 'aspirin'. Interestingly, Nicholas Culpeper, in The Complete Herbal (of 1653) gives a number of uses for willow, including to staunch wounds, but does not mention pain control. The bark of the Cinchona [Jesuit’s bark] gave quinine - a treatment for malaria [caption id="attachment_39935" align="alignleft" width="300"] Amber[/caption] When a tree, like a pine, is injured (through storm damage or insect attack), the bark can produce resin - a sticky and viscous liquid.   The resin is produced in resin ducts present within the bark tissue, though the ducts may be present in deeper tissues. Research has shown that ponderosa pine trees that had more (and wider) resin ducts survived drought and bark beetle attack better.  The resin can harden and help seal wounds . Many resins contain terpenes, such as alpha-pinene and limoneme.  The resin from pine and other conifers can under special circumstances be converted into amber.  Sometimes, the resins produced can be fragrant. Trees of the genus Boswellia and Commiphora produce a aromatic resin that gives frankincense and myrrh respectively.  Both are produced by the wounding of a tree so that its resin seeps out.  Both may be used in the making of incense. Another bark exudate comes from certain species of Acacia - Gum arabic, which forms from the hardened sap (adjacent image).  Acacia species belong to the ‘Bean’ family (Fabaceae).  The gum is collected from trees, mostly in Sudan and the Sahel.  Gum arabic is a mixture of glycoproteins and polysaccharides.  The polysaccharides are constructed from the sugars arabinose and galactose. It is soluble in water and edible, and has a number of uses in the food and pharmaceutical industries. Tapping or wounding the bark of different trees can result in various fluids being released, for example, latex.    White or yellow latex is produced by the rubber tree (Hevea brasiliensis).  The latex is found in special vessels within the bark - laticifers. The process of tapping rubber trees is outlined in some detail here.   Latex production is not confined to woody trees, small herbaceous plants like dandelion and spurge can produce a white, milky latex (as can the opium poppy). [caption id="attachment_39984" align="alignleft" width="300"] Euphorbia latex[/caption] The latex produced by some members of the Spurge family can cause burning pain, inflammation or even blistering - for example that of the Pencil tree.  Such toxic saps most likely evolved to deter animals from grazing. Sometimes, a watery sap may be collected from the bark.  This is the case with Birch.  Sap may be collected (tapped) in early Spring, when sugars and other materials are being mobilised for growth, leaf production etc.  Sap may be collected later but is said to then have a bitter taste.  The sap is an interesting ‘cocktail’ of amino acids, protein, sugars (glucose & fructose), betulinic acid, proteins, vitamins C & B, and minerals.  It is used to make a much favoured drink in Northern Europe and should be consumed within days of collection.  Birch trees are quite sensitive to tapping. Not watery, but very sugary is Maple Syrup. Maple trees are tapped by drilling holes through their bark and into their trunks. Starch is stored in the trunks and roots before winter, it is then converted and mobilised in late winter / early Spring. The collected  sap (through tapping) is then heated to produce a concentrated syrup. Thanks to Montemari at Pixabay for image of gum arabic

There are two main species of walnut tree - Black Walnut and English (or Persian) Walnut.  Walnut trees are often grown in the U.K. as an ornamental or specimen tree in parks or gardens.  However, there are areas where the trees are grown for their timber or the nut crop.  The Black Walnut (Juglans nigra) is native to eastern North America; Missouri is one of the top producers of the nuts.  Whilst the nuts have an intense flavour, their tough coats represent a challenge.  Black Walnuts have had a number of uses over the years, some of them associated with the U.S. military. Read more...

The bedstraws (see previous blog) belong to the Rubiaceae - a family that embraces a number of climbing / scrambling plants.  Another plant from this family is the wild madder (Rubia peregrina). This is a vigorous and evergreen perennial that may be found in hedgerows, and also at coastal locations as it is resistant to wind and salt spray. Its stems have marked ridges / corners (these can be seen in featured photo) consequently these stems are rectangular in cross-section.  They often bear numerous prickles; these prickles help them clamber up and over plants / branches in a hedgerow, not dis-similar to the bedstraws. Read more...

The Turkey Oak (or Quercus cerris) is is a fast growing, tough tree; capable of surviving exposure in coastal regions. It was introduced as an ornamental tree into the UK in the eighteenth century,  being native to south east France across to the Balkans and Turkey.   It often has a long straight trunk (or bole), with branches that are somewhat more slender than those seen on English oaks. The leaves are distinctive and different from those of the native oaks (sessile or pedunculate). Whereas the leaf of the latter is quite broad, the leaf of the Turkey Oak is quite narrow and more ‘angular’ (see featured image);  it is also hairy or downy on its lower surface. One of the tree’s distinctive features is the bark, which has orange fissures near to the base of the trunk. Unfortunately, its timber is of little use as it splits and warps during seasoning. [caption id="attachment_37670" align="aligncenter" width="675"] Turkey oak bark[/caption] The Turkey Oak is considered by some to be a "weed species or pest species" because: it is fast growing it will hybridise with the English oak. it is a host to the Knopper Gall wasp Acorns form and mature some 18 months after pollination and are quite large. They may be an orange / brown at the base,  to a green-brown at the tip. The acorn 'cup' is 'hairy' (see image). The galls that form on the tree are abnormal growths.These galls are caused, in this case, by the development of wasp eggs within the plant’s tissues. The wasp (Andricus quercuscalicis) lays eggs in the catkins of the Turkey Oak, these hatch and develop into wasps which in turn lay their eggs in the flowers of the pedunculate oak. The acorns that form are grossly mis-shapen – and are called Knopper Galls. [caption id="attachment_40042" align="alignleft" width="150"] Gall[/caption] [caption id="attachment_40046" align="alignright" width="150"] Gall[/caption]       In some areas there are now systematic attempts to remove Turkey Oak and other non-native species from woodlands and forests.