Jim Gremel was kind enough to share some of his secrets of preparing a tree for a show by covering the surface of the soil with moss at our January meeting. First, let me say that I disagree with the idea that all trees should receive a covering of moss as their top dressing. Trees that are represented as growing in harsh climates, such as deserts, would be better served in receiving a top dressing of sand or other finely sifted material, so that they don’t look so verdent. However, for many trees, moss is the most attractive way to make the tree seem complete and in harmony with its surrounding.

The first task in putting moss on your tree is acquiring the moss. Much of the information that I am about to impart is based on the book “Moss Gardening” by George Schenk from Timber Press. When collecting moss it is important to realize that the plants you are relocating have very specific needs. If a moss is growing in a shady location in a forest, next to a stream, it is unlikely to survive in the much lower humidity of a bonsai bench area in mostly sun. Collect mosses that are growing on horizontal surfaces, since changing the orientation of a moss or lichen can sometimes adversely affect it. Although it may seem that all mosses are basically the same, in reality there are hundreds of different kinds of moss available locally, not to mention lichens and liverworts. Pay a little attention to how the moss is growing before you collect it. Is it a thin mat on the ground or does it grow in a thicker bun shape? Is it a monotonous green or are there variations in color from silvery-green to yellow or even red? Is the texture velvet smooth or does it have a rougher surface like thousands of tiny ferns? Is it growing in a mostly sunny area or is it in deep shade?

Adding moss to the surface of the soil in a way that makes it look both attractive and natural is only slightly more complicated than it sounds. Moss prefers slightly acidic soil conditions; it will slowly die when exposed to alkaline conditions and is also easily killed by excess calcium. Jim first placed a fine layer of shredded Spaghum moss over the regular soil. Covering the entire surface of the pot can be accomplished by trimming the small pieces of moss so that they fit together like puzzle pieces. Jim depress the edges of the individual pieces with a small spatula so that they form nice looking little islands. Once all the moss has been added, take a bit of very fine Akadama or lava rock and sprinkle it into the crevices between the pieces, adding a little extra so that there is enough to cover any unnatural looking edges. Take a soft brush and sweep it over the surface lightly to remove the excess.

In San Francisco in particular where the climate is moist year round, many people simply encourage the moss that arrives naturally on the surface of their soil. This is indeed one of the easiest ways to get moss on your trees. However, left to its own devices many mosses will form a thick matt over the entire surface of the soil, and begin to grow on the bark of the nebari and the trunk of your tree. As often cautioned, you should remove the moss from the trunk and nebari; you can do this by covering the surface of the soil (or moss) with a cloth or paper towels, then dilute household bleach one tablespoon to a cup of water and use a soft brush to gently remove the offending moss. A thick moss matt is also detrimental to the tree in that it steals fertilizer and water that you intend for the tree and it keeps the soil more moist than a plain soil surface. Remove the moss matt while the tree is on your bench, placing it in a shallow tray to grow on its own. When you are ready to show the tree use it to dress up the surface.

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