Dr James Wearn
Royal Botanic Gardens, Kew
This webpage aims to provide a brief introduction to lichens – intriguing and attractive organisms, which are present all around us.
First of all I should start with a brief description of what lichens are, as one may be familiar with the plants and animals of Berkshire and Oxfordshire, but not with this frequently-overlooked group. Lichens are self-supporting associations between two different organisms, a fungus and an alga or cyanobacterium. Each lichen comprises only one fungal species but may have more than one associate so they always bear the name of the fungus. There are around 1,800 species in Britain.
There are many advantages of looking at lichens.
- Lichens can be seen almost anywhere so whether looking at trees, pavements, roof tiles or walls, lichens are usually to be found! Lichens are often the first colonizers in a habitat and show amazing adaptability to harsh environments. Thus, lichenology is not restricted to a particular type of habitat.
- Lichens are not only attractive but are almost the same throughout the year, with little variation between the seasons and so can generally be identified as easily in the summer as the winter.
There are three main forms of lichen body (thallus). In increasing order of complexity (or ‘shrubbiness’) they are:
- crustose – forming a thin, firmly attached crust over the surface of the rock or tree [for example, the Caloplaca flavescens growing on stone in the photograph at the top of the page]
- foliose – flattened, leaf-like thallus, often attached by small root-like structures called rhizines and can be pulled off with a little effort
- fruticose – shrubby, branched, and often attached to its host via a single ‘stem’
While lichens can be appreciated simply using one’s unaided eyes, a hand lens is very useful in the field in order to see the detail of structures. To safeguard their longevity in our countryside, lichens should only be collected for study or teaching purposes and not where they are rare or where removal from the habitat will cause degradation.
Where to see lichens near Reading
I have only recently been appointed Recorder of Lichens for the area and I am discovering there are many good sites for finding interesting species. There are three main habitat types that are worth observing in the local area – towns, woodlands, and churchyards. Examples include:
- Pavements and concrete walls for the common grey-green lichen Lecanora muralis, a species which has buff to orange disc-like fruiting bodies. It is often mistaken for chewing gum and as such has been informally called the ‘chewing gum lichen’.
- Inkpen Common BBOWT Reserve for Cladonia species on tree bases.
- Various churchyards including those at Checkendon, Swallowfield and Wargrave.
- British Lichen Society [http://www.thebls.org.uk]
- Dobson, F.S. (2005) Lichens. An illustrated guide to the British and Irish species. Richmond Publishing
- Field Studies Council [http://www.field-studies-council.org]
- Purvis, W. (2007) Lichens. Natural History Museum, London
- Wearn, J.A. (2009) Fascinating Lichens. Fact sheet [please email me if you would like a copy]
Showing lichens on an old tree stump to members of the society.
BBOWT Reserve at Inkpen, 7 March 2009.
[From left: Roger, Me, Laurie, Dot, Graham, and Ricky]