#71 - September 2023 - Garden Stuff - © Sandy Lang - slang@xtra.co.nz LICHENSSept/Oct: Mid-spring. Birds anesting, bees abuzzing. Water mains aleaking, summer El Niñoing. Prepare for drought. (1) Get a roof-water tank and (2) Get mulching (increase soil water capacity, slow surface water loss).Lichens: Pronounced ‘liken’ (USA) or to rhyme with ‘kitchen’ (UK). A lichen’s body (thallus) is a matrix of fungal threads (hyphae) (~90%) with unicellular algae and/or cyanobacteria embedded in it (~10%). Lichens are a classic example of symbiosis - a mutually beneficial relationship between quite different organisms. Fungi are not plants. Algae / cyanobacteria are not plants either. Roles: The algae / cyanobacteria photosynthesise (do the job of leaves) to produce sugars which they share with the fungus. The fungus protects the algae/cyanobacteria and its hyphae anchor it to the substrate and capture whatever water/minerals they can from it (do the job of roots). They also exude harsh chemicals that etch rock, help weather it, so creating soil. Some lichens ‘fix’ atmospheric nitrogen - they make nitrate fertiliser from the air. There are 20,000 lichen species. They grow very slowly (~1 mm /year). Some individuals are over 8,000 years old. Lichens cover ~7% of the land surface.Appearance: Some lichens look like bird poop, others look a bit leafy and are wrongly called “mosses” (mosses are true plants, nothing to do with fungi, or algae, or cyanobacteria). Often lichens are just a coloured smear on a tree or rock. They come in a range of drab or bright colours. They change colour when wet. They are identified by colour (when dry) and by their surface texture, using words nice like ‘squamulose’.Substrate: Lichens grow on any surface, anywhere. They are pioneers, growing on freshly exposed rock, on tree bark, on roofs, on cars. Some also grow on loose substrates (soil, sand) stabilising them so plants can establish. Some lichens live on rocks undersea, others under freshwater, others on beach pebbles. Some attach to nothing at all (‘vagrant lichens’) and blow about in the wind. Lichens live about everywhere - at sea level, on high mountains, in hot dry deserts, on frozen arctic tundra. They are not killed by total desiccation, or freezing, or baking in the sun. Uses: Some lichens can be eaten. Others are poisonous. Some are sources of traditional fabric dyes (Harris Tweed). Litmus paper (think school chemistry) is made from a lichen. ___________________________________