Are you able to tell me how I can get lichen to grow on totara fence posts?
The best way to get lichen to grow is to provide a friendly environment for it, and allow it to find its own way there.
Most lichens grow very, very slowly, often less than a millimeter per year, and some lichens are thought to be among the oldest living things on Earth.
Check out this article, Growing Lichens on your walls and trees
For more lichen info visit www.earthlife.net
For those that want to remove lichen - it is not recommended that lichen be removed from an organic garden, as it is a good indicator of the absence of pollution and also harbours beneficial insects - but if necessary, try water-blasting, rubbing, scrubbing or a certified organic weedkiller.