Lichen and Iceland moss: traditional uses, forms and cautions

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Lichen is not a plant at all: it is a fungus living together with an alga or a cyanobacterium. One species, Iceland moss, has sat in European home-remedy cupboards for centuries — bitter, slippery, and simple to prepare as a cold macerate or a honey syrup. This page explains which lichen is used, in what form, what it tastes like, and which ones to leave well alone.

What it is credited with

• Iceland moss is traditionally used in European herbalism for dry, tickling coughs and a scratchy throat, on account of its mucilage, which coats as it goes down.
• In German pharmacy practice, Iceland moss has long been the base of cough lozenges sold over the counter — a use still visible on shelves today.
• Herbalists class it among the bitter tonics, with a reputation for a jaded appetite, sluggish digestion and the worn-out feeling that follows a long convalescence.
• Oak lungwort (Lobaria pulmonaria), lung-shaped and once read that way by the doctrine of signatures, had a folk reputation for chesty, rattling coughs; it appears in some modern cough syrups.
• Common yellow wall lichen (Parmelia parietina) was used by old apothecaries as a bitter stand-in for cinchona bark when feverish chills set in.
• Usnea species — threaded lichen (Usnea plicata) and its relatives — have a tradition, in folk practice, as a drying wash for grazes and small skin irritations.
• Naturopathy values lichen mostly as a mucilage-and-bitters combination: soothing and slippery on one hand, stimulating to the appetite on the other.

How to use it

The bitter compounds are the active fraction, and hard boiling wrecks them. So the gentlest methods come first.

• Cold macerate (the classic). Put a small handful of shredded dried Iceland moss in a jug of cold water. Leave it on the worktop overnight, strain in the morning. It comes out pale, slippery and frankly bitter.
• Warm infusion. Pour hot — not boiling — water over a heaped teaspoon of the shredded lichen per cup. Cover, steep a quarter of an hour, strain. Taken one cup at a time, morning or evening.
• Honey decoction, to tame the bitterness. Bring water to the boil, drop the lichen in, then tip the water away and rinse the lichen under cold water — this washes out the harshest bitterness. Return it to fresh boiling water, hold it just below a simmer for half an hour, then stir in honey generously and let it stand ten minutes. Strain. Keeps a few days in the fridge.
• Lozenges. The ready-made pastilles from a pharmacy are the simplest route for a dry throat, and the dosing is done for you.

In the kitchen and around the house

• As flour. Nordic households ground washed, dried Iceland moss and worked it into bread and cakes — a lean-season food, not a daily flour.
• In cooking abroad. Rock tripe (Umbilicaria) is eaten in Canada; in Japan, Umbilicaria esculenta — “iwatake” — goes into tempura, soups and mixed salads. In British Columbia, bear’s hair lichen (Bryoria fremontii) was cooked into puddings with elk fat and berries.
• Dye pot. Lichen pigments colour Scottish and Irish tweeds. They are slow to extract but notably resistant to fading in water and light.
• Always wash first. Rinsing and repeated water changes remove bitterness. Lichen is difficult to digest in any case, and some traditional recipes called for very long cooking.

Frequently Asked Questions

The one thing to remember: buy dried Iceland moss labelled Cetraria islandica, rinse it, and make it as an overnight cold macerate or a honey decoction — never gather unidentified lichen to swallow.

Is all lichen safe to eat?

No. Several species are poisonous because of the usnic or vulpinic acid in their tissues, and the list of dangerous lichen-fungi continues to grow. The compound in Cetraria pinastri slows the respiratory system and has proved fatal. Only use a species you have bought clearly identified.

Why does Iceland moss taste so bitter, and can I fix it?

The bitterness comes from lichen acids, which are also what herbalists value in it as a bitter tonic. Blanching it in boiling water, tipping that water away and rinsing under cold water removes much of the harshness. Honey in the finished decoction does the rest.

Should I boil lichen for a herbal drink?

Hard boiling damages the bitter fraction, so a cold macerate left overnight or a warm infusion in hot-but-not-boiling water is the usual approach. The honey decoction is the exception: there, the blanch-and-rinse step is deliberate, to strip bitterness before the long gentle simmer.

Can I scrape lichen off my garden wall or a tree trunk?

For a dye pot, perhaps. For anything you intend to swallow, no. Lichens absorb airborne pollutants and heavy metals, which is why they serve as pollution indicators, and identifying them correctly is genuinely difficult. Buy dried, labelled material instead.

When can lichen be gathered?

Iceland moss can be collected in any season, since it does not die back. In practice it is easiest in damp weather from late spring to early autumn, when the thallus is soft rather than brittle. Dry it thoroughly, then store it airtight in the dark.

This information is provided for general interest and reflects the traditional use of plants. It is not a substitute for medical advice. If you are on medication, pregnant, or in any doubt, ask a healthcare professional.