We get a lot of repeat questions at the nursery, and one of the common ones is “What’s this moss stuff growing on my trees bark? This moss is a form of lichen, which is a wonderful little ecosystem of fungus and algae or bacterium. Pretty to look at, this symbiotic colony will form on rocks, old and dead trees, fence posts, really anything standing still in nature.
Lichen is harmless when found growing on non living things, but is an indicator of the health of a living tree. If a fruit tree is growing at its correct rate, the outer bark is sloughed off, much like we slough off our outer layers of skin. This sloughing prevents lichen from colonizing. So when we see lichen in fruit orchards, we begin looking for the under lying reasons for why the trees are not growing at their correct rate. The usual culprit is lack of fertilize or water, easy to solve issues. It often takes much more fertilizer than most people apply, to keep fruit trees happy. Here are some guides to read about the correct fertilizer for your fruit trees.
-Grass growing under the trees- A young fruit trees doesn’t compete well for food and water with weeds or lawn grass. It is best to keep the area under the trees canopy mulched or weeded.
-Wrong soil pH- Having the wrong soil pH can tie up nutrients, and make the fertilizer you are applying, unavailable to the tree. Have a soil test run, and lime or acidify your soil, to get the best results from your fertilizer.
-Lousy soil- Some soils are just well… just lousy. We garden in the sand lands and the soil lacks nutrients. When gardening in sand, make sure you mulch heavily under your tree canopy. Use a mulch like spoiled hay that will break down fast, and build your soils organic content. This enriching process will help your soil hold onto the fertilizer and water you do apply much better.
-Lack of Sun- Fruit trees need a lot of sun to grow well. Planting in shady sites will lead to weak slow growing trees. If lack of sun is the case, and the trees are still young, (first and second year) you should move the tree to a sunnier location.
Some people wonder if they should kill the lichen. Remember this moss is harmless, if the colony is small, just work on the issues that are allowing the lichen to form. On heavily infested trees, that you think you can rescue, you can use a liquid copper spray to kill the moss or just gently rub it off.