Lichen
Lichen is a living partnership in which a fungus grows with a photosynthetic partner, usually a green alga or cyanobacterium. Together they form a distinct body that can look like a crust, leafy patch, or tiny shrub. Lichens are not plants or mushrooms, though fungi are central to their structure.
- Partners
- Fungus plus alga or cyanobacterium
- Body
- A thallus with varied forms
- Habitats
- Rocks, bark, soil, and more
- Not plants
- Lichens are not mosses
- Not mushrooms
- A lichen is a partnership
What is a lichen?
A lichen is an association built around a fungus and a partner that can make food from light, usually a green alga or a cyanobacterium. The fungal partner provides much of the lichen’s body and helps shelter the photosynthetic cells. Those cells make sugars that can be used within the association. Researchers also find other microorganisms in some lichens, so a lichen can be more complex than a simple two-part pairing.
The visible body is called a thallus. It may be leafy, branching, powdery, jelly-like, or a crust tightly attached to a surface. A lichen’s appearance depends on its species and growing conditions, and some types are hard to notice. The word “lichen” describes this organized partnership, not one single species. Different lichens have different fungal partners, and their partners do not all interact in exactly the same way.
- 1Fungal start
A fungal spore begins growing as a network of hyphae.
- 2Partner meeting
The fungus encounters a compatible alga or cyanobacterium.
- 3Association
The partners establish a shared relationship and exchange resources.
- 4Thallus growth
Fungal growth forms the visible body around or among photosynthetic cells.
- 5Continued growth
The lichen expands when conditions allow, often slowly.
How does a lichen form and grow?
In many lichens, fungal spores begin the fungal partner’s life, but a spore does not necessarily carry an alga with it. For a lichen association to develop, the fungus must meet a compatible photosynthetic partner. If they establish together, fungal threads called hyphae grow around or among the partner’s cells. The resulting thallus grows slowly, often adding to its edges or branches over time.
Lichens do not have roots like plants. They take in water and nutrients across their surfaces, and many can become dry and inactive when conditions are harsh, then resume activity when moisture returns. This helps explain why lichens can live in places with little soil. It does not mean every lichen thrives everywhere: species differ in their needs, including the surfaces, light, moisture, and air conditions they tolerate.
A lichen is an association centered on a fungus and photosynthetic partner.
Its appearance may seem plant-like, but the fungus forms much of its body.
Lichens range from crusts and powders to leafy forms and tufts.
Editorial placement to help compare; not a measurement.
Where do lichens live, and why do they matter?
Look closely at tree bark, rocks, old walls, gravestones, and exposed soil, and you may find lichens in patches or small tufts. Some grow on leaves or hang from branches; others live in very cold, dry, or exposed places. A lichen growing on a tree generally uses the bark as a place to live rather than drawing food from the tree. Lichens can also colonize bare surfaces, including newly exposed rock.
Lichens contribute to ecosystems in several ways. Some help make nutrients available as they grow and break down, and many serve as food or habitat for small animals; reindeer, for example, eat certain lichens. Their presence and growth can also provide clues about local environmental conditions, though interpretation takes care. Because some lichens grow slowly and persist for a long time, researchers can use their growth patterns to help estimate how long a surface has been exposed.
| Lichen | Mushroom | Moss | |
|---|---|---|---|
| What it is | Fungus-partner association | Fungal reproductive structure | Small green plant |
| Main partners | Fungus and photosynthetic partner | Fungal cells | Plant cells |
| Common forms | Crust, leafy patch, or tuft | Cap, stem, or other forms | Soft green cushions or mats |
| Typical places | Bark, rock, soil, walls | Soil, wood, or other substrates | Damp soil, rocks, tree bases |
Is lichen a plant, moss, or mushroom?
No. A lichen is not a plant, moss, or mushroom. Moss is a small plant, while a mushroom is a reproductive structure produced by certain fungi. Lichen is a partnership whose visible body is largely formed by its fungal partner. The names can be confusing: some lichens have “moss” in their common names or resemble miniature shrubs, but resemblance does not make them close relatives of mosses.
Lichens are familiar natural growths, but appearance alone is not a reliable way to decide whether something is safe to eat. Some lichens have been used as food in particular cultures, while others are unsuitable or may contain irritating or harmful substances. Do not eat a wild lichen based on a photo or a common name. If you are curious about a specimen, observe it without tasting it and ask a qualified local expert for identification.
How does lichen connect to mushroom biology?
Lichens are useful to learn about alongside mushrooms because both involve fungi, but they are not the same kind of thing. A mushroom is a structure made by a fungus, often for producing and dispersing spores. A lichen is a lasting association involving a fungus and a photosynthetic partner. In both cases, fungal hyphae are important: these fine threads form networks and contribute to the structure of fungal growth.
Lichens also show why the word “fungus” covers many different ways of life. Some fungi form lichens, others live in soil or wood, and some produce the mushrooms people recognize. Studying lichen structure can introduce ideas such as fungal partners, hyphae, and spores, while mycology—the study of fungi—covers lichens as well as mushrooms. These connections are helpful, but they do not make lichen a mushroom or a type of edible fungus.
Common questions about Lichen
Is lichen a fungus?
A lichen includes a fungus, but it is not just a fungus growing alone. It is an association between a fungus and a photosynthetic partner, usually an alga or cyanobacterium. The fungus typically makes much of the visible structure, while the partner makes food using light.
Is lichen the same as moss?
No. Moss is a small plant; lichen is an association involving a fungus and a photosynthetic partner. They may grow beside one another or look similar from a distance, and some lichen names include the word “moss.” Those similarities do not mean they are closely related.
Where does lichen grow?
Lichens grow on many surfaces, including rocks, tree bark, soil, walls, and gravestones. Some occur on leaves or hang from branches. Different species have different habitat needs, and some tolerate conditions that are too dry, cold, or exposed for many other organisms.
Can you eat lichen?
Do not eat a wild lichen based on appearance or an online identification. Species differ, and some may be unsuitable or harmful. Although certain lichens have been used as food in some cultures, that does not make an unknown specimen safe. Consult a qualified expert rather than tasting it.
Related terms
Explore on Pscilly
Sources and further reading
Written by the Pscilly editorial team and reviewed November 2026. Educational content only, not medical or legal advice. Pscilly does not sell psilocybin. Never eat a wild mushroom without expert identification.