Encouraging Algae, Moss and Lichen

If you have a pristine new stone wall or other stone feature you may be keen to see moss, lichens and algae establish themselves, to give a more aged appearance. A simple way to speed things along is to apply a thin paste of flour and milk laced with concentrated liquid seaweed fertiliser over the surface of the stones or bricks. This will provide fertile ground for algae and moss spores. Lichens may also establish themselves, although they are also heavily dependent on good air quality. Once moss and lichens are established they are able to gather enough water and nutrients from rainwater and the substrate surface (wall) and should spread easily.

Lichens and Air Pollution

Air pollutants such as sulphur dioxide are extremely damaging to lichens and can prevent them from growing. This makes lichens good natural indicators of air pollution. For instance:

  • bushy lichens need clean air
  • leafy lichens will grow even if there is some air pollution
  • crusty lichens can grow in more polluted air.

If there are no lichens present in a site that would otherwise seem to be ideal for them, this suggests that air quality is very poor.

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