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Liking the Lichen

This article was first published on 20 Mar 2018.



Photo by the Otago Daily Times

Lichens are fascinating, yet easily overlooked.  In Dunedin Botanic Garden you can spot them growing on tree trunks, covering boulders in the Rock Garden and on the fence bordering the herb garden.

Lichens are not just one organism but two or more organisms living together in a symbiotic relationship.  In this mutually beneficial agreement the photobiont (algae & or cyanobacteria) provides the mycobiont (fungi) with nutrients via photosynthesis.  In return, the mycobiont absorbs moisture and provides the photobiont with shelter, minerals and sometimes protective sunscreen. Together they can grow in various, even harsh conditions and habitats, beyond the limits of other plants.
There's a common misconception that lichens are harmful to trees; this is not the case. Lichens shallowly attach themselves or perch upon the bark of trees; they are not parasitic. The presence of lichen on healthy trees should be welcomed - studies show that the greater variety of species present, the greater the air quality.  Over 100 different species of lichen grow in the Botanic Garden, a great showcase for Dunedin's clean air!

Globally there are approximately 20,000 known lichens.  New Zealand has an exceptionally rich lichen flora, at around 2,000 species. They are a food source for many native and introduced invertebrates, which in turn provide food for native and garden birds.  Lichens are also used to produce antibiotics and dyes.

Lichens are typically the first organisms to colonise bare rock, a pioneer species and the initiator of the soil-production process.

Garden Life is produced by Dunedin Botanic Garden. For further information contact Stephanie Sinton.