Why Lichen and Moss Deserve a Place in Your Garden

Lichen and moss are among the oldest living things you will ever welcome onto a tree. Neither is a parasite. Lichen is a partnership between fungi and algae, whilst mosses are simple plants that cling to bark without taking nourishment from the tree itself. They use trunks and branches as a place to live, not a meal. In return, they add texture, colour and wildlife value to any British garden or woodland. A tree coated in soft green moss and grey-green lichen is not neglected; it is a small ecosystem. These organisms also tell you something valuable: many lichens are sensitive to air pollution, so a healthy population suggests clean air and stable humidity. If your trees are rich in them, your garden is doing something right.

What Lichen and Moss Need to Thrive

Encouraging these slow-growing companions is less about planting them and more about creating the conditions they love. The key requirements are consistent moisture, moderate shade, and undisturbed bark. Different species have different preferences, so variety in your trees will bring variety in lichen and moss. Crustose lichens form flat, crusty patches; foliose lichens are leafy; fruticose lichens are shrubby. Mosses range from feathery cushions to trailing threads. All of them appreciate:

• Humidity: Damp air is more important than wet roots. A nearby pond, stream or even a regularly filled bird bath can raise local humidity.
• Shade: North and east-facing bark stays moist longer. Deep shade suits many mosses, whilst dappled light encourages lichens.
• Rough bark: Oak, ash, willow, field maple, hawthorn and elder have textured bark that holds moisture and gives spores a foothold.
• Age: Older trees have had decades to accumulate colonies. A mature oak or ash is a treasure beyond price.
• Clean air: Avoid areas downwind of heavy traffic or intensive agriculture where ammonia and nitrogen oxides can harm sensitive lichens.

Choosing and Caring for Trees That Encourage Growth

If you are planting new trees, choose native species that suit your soil and climate. A mix of oak, birch, rowan, field maple and willow will provide different bark textures and moisture levels. But the most important step is to look after the trees you already have. Do not pressure-wash bark, and never apply insecticides, fungicides or high-nitrogen fertilisers around the trunk. These destroy the delicate communities you are trying to encourage. Prune only when necessary, and leave lower branches on garden trees where possible. That extra shade keeps the bark damp. Allow leaf litter to remain beneath the canopy; it acts as a mulch and holds moisture in the air close to the trunk. If you have an old tree that is safe, leave it standing. Deadwood is not waste — it is a habitat.

Practical Ways to Boost Humidity and Shelter

British weather helps, but you can tip the balance in drier parts of the country. Plant trees in groups rather than as isolated specimens; a cluster holds humidity far better than a single trunk. Create a windbreak with native hedging to reduce drying winds. Underplant with shade-loving perennials such as ferns, wood anemone and wild garlic, which keep the air beneath the canopy cool and moist. Leave ivy on some trunks — it adds shelter and humidity — but keep an eye on it so it does not smother the canopy. If you have a very dry garden, a small wildlife pond or even a sunken water butt nearby will raise humidity for metres around. Avoid south-facing, exposed positions for trees you want to festoon with moss.

• Retain deadwood, both standing and fallen.
• Mow less beneath trees; let the grass grow long.
• Water the soil, not the bark, during prolonged drought.
• Never scrub or jet-wash trunks and branches.

Woodland Planting and Long-Term Stewardship

In a woodland setting, the principles scale up. Aim for a continuous canopy with trees of different ages. Thin carefully rather than clear-felling, as sudden exposure dries bark and kills lichen. Leave old trees undisturbed — they are the reservoirs from which spores spread to younger trees. Retain deadwood on the ground and as standing stumps. If you manage a woodland, consider leaving a few trees to grow old gracefully rather than harvesting them all at the same time. Lichen grows millimetres a year, and mosses are not much faster. This is a long game. Record what you see: photograph new colonies, note their colours and forms. Over years, you will witness a slow, quiet increase that rewards patience. The oldest trees in your care are the most valuable. Let them be.