How to Identify Lichens

Identifying lichens can seem daunting at first — there are thousands of species in Britain, and many are tiny, subtle, or look very similar. But with a little guidance and a few simple tools, anyone can start recognising them in the field. Lichen identification is as much about learning to observe carefully and understand habitats as it is about knowing Latin names.

Getting Started: Tools and Essentials

You don’t need a laboratory to enjoy lichen identification, but a few tools make the process much easier. A good hand lens is the most important; even 10x magnification lets you see surface textures, tiny fruiting bodies, and reproductive structures. A camera or smartphone is useful for documenting finds, especially if you want to compare them later or ask for help with tricky specimens. A notebook is invaluable — recording habitat, substrate, and environmental conditions helps with identification and makes your observations more meaningful.

Tools to Take Into the Field:

Hand lens (10x–20x) – essential for examining small structures.
Camera or smartphone – to photograph specimens for later reference.
Notebook & pencil – jot down habitat, substrate, and field notes.
Optional: small knife or scalpel for examining medulla (stay up to date with current laws for carrying blades).
Optional: Chemicals for spot tests (K, C, P), UV torch for fluorescence.

Most beginners can make great progress with just a hand lens, camera, and notebook, while optional tools allow for more advanced identification of tricky species.

Growth Forms: The First Clue

The easiest way to start is by recognising the growth form of the lichen. There are three main types: crustose, foliose, and fruticose, and these give your first clue to the species.

Crustose lichens form thin, crust-like patches that are tightly stuck to their substrate. They often appear as colourful smears on rock, bark, or soil and are difficult to remove without damage. Crusts can be tiny and inconspicuous, or cover large areas of exposed stone. Foliose lichens are leafy and often attached at a single point or several small points, but their lobes are free, giving them a three-dimensional appearance. These are the lichens that are easiest to spot and photograph, like the upland Rock Tripe (Lasallia pustulata) or the oceanic Lobaria pulmonaria in woodlands. Fruticose lichens are more bushy or hair-like, sometimes forming shrubby clumps or hanging “beards” from trees. Usnea species, known as Old Man’s Beard, are a familiar example.

Recognising the growth form immediately narrows down the possibilities, and when combined with knowledge of the substrate and habitat, you can often identify a lichen in the field.

Habitat Matters

Where a lichen grows is often as important as how it looks. Some species are almost exclusively found on particular types of rock, while others prefer certain tree species. Siliceous rocks in upland areas support a different set of lichens than limestone pavements, and coastal cliffs have their own specialised species adapted to salt spray. Woodland species favour particular trees or shaded microclimates, while some lichens thrive in man-made habitats, from gravestones to stone walls. Observing these environmental cues — substrate, moisture, light, and exposure — is one of the most powerful tools in lichen identification.

Field Identification

Many lichens can be identified in the field using careful observation, a hand lens, and a good guidebook. Larger foliose and fruticose species, or distinctive crusts, are often straightforward. Others, particularly tiny crustose species or members of complex genera, can be much harder and may require closer examination. Noticing the colour, texture, edges, reproductive structures, and any changes after rain will help. Some lichens dramatically change appearance when wet, swelling, darkening, or revealing previously hidden structures. Returning to a site under different conditions often reveals new details.

Patience and Observation

Lichen identification rewards patience, curiosity, and careful observation. Start with the larger, obvious species and gradually build your experience with smaller and more subtle forms. Documenting what you see, noting microhabitats, and revisiting sites under different conditions all deepen your understanding. Over time, you’ll start noticing patterns in growth forms, substrates, and habitat preferences that make identification quicker and more intuitive.