Visitors to the RHS Hilltop – The home of Gardening Science – were introduced to the wonderful world of lichen during a talk and walk on the 3rd August.
The talk emphasized the novel and clever way that lichens feed. They don’t have to digest organic matter as the rest of the fungal kingdom do. Instead, they share their life with a second organism that makes food for both partners.
This second organism is often an alga which lives totally enclosed and protected by the fungal partner. The alga combines carbon dioxide, water and sunlight to form sugars using same process of photosynthesis that other plants use.
The fungi that form lichens are able to produce a wealth of special chemicals to help the partnership live in some very inhospitable places. Roofs of houses, for example, get very hot and dry on a summer’s day! They’re not a place where you would expect to find fungi or algae growing separately.
Fungi adapted to grow as lichens protect their partners in a multiple of ways. Including producing sunscreens to protect their partners from excessive UV radiation and grazing deterrents that make the lichen less palatable to slugs and snails.
The follow-up walk in the orchard gave visitors an opportunity to see lichens on trees and to observe how fungicide treatments, designed to reduce fungal diseases on the fruit trees, prevent lichens growing on the bark. Trees sprayed less frequently, or not at all, supported more lichens and more species of lichen.
Spraying in the orchards at RHS Garden Wisley is being phased out in favour of other methods of disease and pest control. It will be interesting in future years to see how quickly trees are recolonized by lichens.