deciduous trees at this time of year from grey skeletal shapes that are just beginning to come into leaf to individual tapestries of earthy blues, greens, yellows and browns, a quality that is largely hidden later in the year.
All lichens are sensitive to atmospheric pollutants, which are absorbed over the whole of their surface and they are a good indicator of environmental health. Most lichens cannot survive where air quality is poor. If you can find a tree that’s over
20 years old that has no lichen at all on its bark, the chances are that it’s growing in a polluted atmosphere, so, having found it, move on! Amazingly, there are more British
lichen species recorded – over 18,000 of them - than there are native green plants, and more are being discovered each year! Many different lichen species can be found in the Four Shires, but one of the commonest and easiest to spot is the species called Xanthoria parietina. (Xanthoria derives from the Greek and means golden and parietina
comes from the Latin word for wall.) Xanthoria has the common name of Golden Shield and consists of flat, frilly rosettes coloured bright ochre that shade to tinges of emerald where there is less light such as on the underside of twigs. Arising from its surface there may be clusters of cup-shaped protrusions that are often light tan rather than yellow. These are the fruit bodies of the fungal part of the organisation. Different species have different
preferences with regard to chemicals in the air and Golden Shield prefers a nitrogen-rich environment, on trees and buildings on farmland and roadside hedges for example. A general increase in the amount of nitrogen being produced from vehicle exhausts, fossil fuels and livestock has led to this particular lichen becoming very widespread. Twigs and branches in hedgerows,
particularly those of elder bushes and where birds often perch, may be thickly clothed and are an impressive sight when spring sunshine highlights the rich golden colour. We know that lichens have been
around for a long time. Because they are composed of soft tissue, fossil records are sparse, but the earliest British lichen-like fossil was discovered in Aberdeenshire and placed at about 410 million years old!
On a shorter timescale, the useful
properties of lichens have been valued for centuries. The Golden Shield, and many other species have been used to make natural dyes, most of which have now been replaced by synthetic versions. Up until the 19th century much of the yarn used in Harris Tweed was dyed with extracts from the different forms of lichen that were plentiful in the north west of Scotland and closer to home, cudbear, one of the ingredients used to colour Shutford plush was derived from lichen. Until chemical colouring agents could be synthesised, tons and tons of lichen were used in the dying industry. Many of the shades are earthy
greens, yellows and browns, but rarer, mainly continental species of lichen produce reds and purples. These were valued in Roman times and were used to colour the clothing of the elite. Some craft workers still like to use natural substances to dye their yarn. For this purpose extract of lichen has the advantage that when dying wool or silk it doesn’t need another substance – a mordant – as a fixative. It is important to remember that unlike when you pick a mushroom, which involves taking only the fruit body, if you harvest lichen you are removing the whole organism and lichens take years to grow. Deep colours need large quantities, but subtle shades can be achieved with quite small amounts. Preparations from lichen species
have in the past performed a variety of other functions too. Litmus, the pH indicator is made from certain types of lichen, and some species have antibacterial properties, which led to them to being used as a constituent of healing skin lotions. Wadding for shotguns, powder 4
• Several lichen colonies on a stone wall
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