The Moss Myth

I remember the days when moss was the enemy. The idea was that moss impeded water penetration, or kept the pot too wet. So it was a surprise when I was an apprentice that Mr. Suzuki encouraged moss to grow on the soil, and I discovered there were some advantages to having it there.

Shredded sphagnum moss on top of volcanic soil (akadama/pumice) at 1/8-1/4″ thickness, with shredded live moss added to inoculate. I often add ink to it so it’s not straw colored while the moss gets established. Be sure you use true sphagnum moss, not peat moss. Peat moss is rotted sphagnum, and tends to be water repellent when dry. The best sphagnum to use is sold often as ‘orchid’ moss, and is straw colored and is like a sponge when sprinkled with water.

If applied in the early spring around repotting time, a carpet of live moss will be well established by summertime. This photo was taken in June and looked like the above photo in February. Even sphagnum applied in early summer will have great benefits, although the live moss might not get established in the summer heat.

The advantages are these:

1-Assists in water holding capacity near the surface, where it dries out the fastest

2-Creates much greater root growth in the top layer of soil that is otherwise too dry for roots. Since a bonsai pot is a greatly limited space, this is very significant.

3-Prevents soil erosion

4-Gives a year-round feeling of stability, age, and cleanliness

25 Comments

  1. Ken Krogholm says:

    Hi Michael, Thanks for bringing this topic to our attention – it is often an overlooked part of growing bonsai. Just one question for you. I collect yamadori scots pines and always add freshly cut long-fibered moss which happens to be abundant at the collecting sites. I have great faith in the benefits of using this type of moss – but after about a year or so – the various types of mosses establishing themselves in the long fibered moss – start growing up the trunks and in an between the fine bark layers. It is very difficult to manually remove this moss as it usually ruins the fine bark layers – so how do I get rid of this moss without ruining the precious bark?? Does Mr. Suzuki face the same problem in his garden?
    Regards from Ken Krogholm (Denmark)

    • crataegus says:

      Yes moss growing on the trunks of pines in particular is a real problem. Cleaning that out without losing the bark is hard to do. There does not seem to be a magic bullet. I have found that getting rid of as much as possible by tweezers is best, as when its dead it is harder to remove. Then kill what remains with one of several things. I’ve used 50/50 vinegar/water, although the moss comes back eventually. Some use lime sulfur which definitely kills the moss but leaves a white trunk too.

  2. Ross Munro says:

    This answers a question I’ve had for a long time – whether to discourage or encourage mossy growth. Thanks.

    • crataegus says:

      It works well for the soil mix I use, which is very porous, and volcanic, and dries so fast on the top. A highly organic soil might be another matter.

  3. Daniel Dolan says:

    Michael:

    The beautiful close up image of your moss at summer appears to be in full sun….at least for the benefit of this photo. Or, is this one of the few varieties that actually grow in the sunlight?

    I dread asking this next question……..as I fear the answer will require some skill I don’t have….but, with moss covering the surface……..how do you know when to water? I have heard by the weight of the pot…….or by experience of the daily temperature effects…..or “just by looking at the tree I can tell.” Please tell me you use a chopstick in the soil to measure moisture below the surface of the moss.

    Lastly, doesn’t moss require moisture in excess of the trees requirements….the most common observation?

    Finally, knowing you appreciation for books about Bonsai I have a new idea for a Bonsai book that no one has ever considered writing to my knowledge……….The message is: Bonsai are very nearly impossible to care for properly!……..actually this is the title.

    Best regards,

    D/D
    Chicago

    • crataegus says:

      It does seem a trick, knowing when to water with live moss on the surface. But dry green, live moss and wet green, live moss look totally different. You’ll pick it up very fast. Weight of the pot is for those with better sense of physics than I… Looking at the situation at the surface of the pot is a much better indicator of water needs. I don’t use a chopstick in the soil, although that might not be a bad idea for a tree with a very weak and spindly root system and you’re worried about overwatering. The tree will be happy if the moss is happy— and I say that with one caveat: I use a fast draining pumice/akadama mix and other mixes, especially those with organic components like peat moss may give a very different ‘read’ when they have moss on them. I just am doing what I did in Japan and it has great results. Try not to mix and match programs; live moss on this soil mix works well for keeping that top layer full of roots and moist, so that the whole pot dries out at the same rate rather than the top becoming desiccated and the bottom staying too wet. I can’t say about other soils.

      Moss will grow in full sunlight if it has enough moisture. There are types that are very shade preferential, though, and it’s best to collect your moss from a sunny location. Look for the short knapped moss, not a fibrous stringy, wandering kind.

      Great question!

  4. Sam Ogranaja says:

    Michael,

    Thank you so much for taking the time to address this. I too was under the impression that year round moss would ultimately be a detriment to our trees but I also use a VERY porous soil mix which generally requires watering twice a day in the summer heat. Is there a certain moss which is better to use, meaning more sun hardy? My trees get full sun from 9 AM to about 7PM. My maples hide underneath a big cherry tree as this much sun scorches the leaves.

    I truly appreciate you keeping up with this blog. I hope to be able to attend the Artisans Cup of Portland 2013.
    Have a fantastic weekend!!!!
    Sam

    • crataegus says:

      Yes, there are sun mosses and those that prefer shade. Take a look at a recent reply to a comment on moss–

      One thing I did not mention is how to establish the moss on a porous soil. First, it’s best done in spring or fall, when it can get established before summer. What is best is to take some orchid moss—straw colored true sphagnum—and pass it through a coarse soil sieve, then crumble up or sieve your live moss to inoculate the batch. Wet it down a bit, then apply it to about 1/8″- 1/4″ thickness. The sphagnum will keep that top layer moist and the live moss should grow in it.

      There are several mosses that will work well in the sun, try to find those that are growing in the cracks in sidewalks and the like, those that can take heat and sun. Some are silvery or reddish and those look nice with trees, and don’t upstage them. The real vibrant green mosses look odd.

      • William says:

        When you say “pass it through the course soil screen” which part of the moss do you put on the soil? The course or the sifted?

      • crataegus says:

        I use the sifted. But the unsifted moss also has applications, such as areas of high wind or for azaleas and such.

  5. Mary Miller says:

    Another thing to keep in mind is where you live!

    When I was living in Miami, FL students continually tried to “import” moss from other parts of the country. Rarely did it grow. Why did they do that? I don’t know. We had great moss right in our own backyard!

    “The moss is always greener …” or something like that.

  6. Jimmy Le says:

    Hi Michael,

    What do you do when it comes to putting organic slow release fertilizer (like the green dream stuff ) on your soil? Can you still just sprinkle it on top of the moss?

    • crataegus says:

      The cake or pellet organic fertilizer is best placed in particular locations rather than scattered. That way you’ll be able to grow moss…the moss under and adjacent to the fertilizer will die, because it’s very sensitive to fertilizer. Also, for some trees, you’ll want to take the fertilizer off at some point for training purposes or in the fall when you don’t want it anymore, and if it’s in piles you can do so much more easily. On old trees place it in the corners of the pot, stay away from nebaris when you can.

  7. Peter says:

    What type of ink do you use?

  8. Peter says:

    So glad to read this article….I love moss on my Bonsai pots…one hears so much negativity it’s a relief to read your comments…ps I loved reading your book, cheers, Peter

  9. Reblogged this on Kitora no do and commented:
    Muschio

  10. graham says:

    moss is ok on the soil but i have it growing on the branches and twigs i am worried this will damage the new buds its a bonsai larch forest i have had for about 20 years is there a way of killing the moss without damage to the trees

    • crataegus says:

      Moss will not trouble the buds. They will come out fine. But if you don’t want the moss—too much can rot the bark off pines for instance—then you can try to spray a 50/50 solution of vinegar on the branches. Be sure to cover up the pot when you do this as you don’t want that in the soil. (And DO NOT do this when the buds are opening or when there are leaves or needles on the tree!) The moss will die, but it usually comes back, too.

  1. […] What’s the moss myth? You can find out at Micheal Hagedorn’s Crataegus Bonsai blog. […]

  2. […] subject so….here we go! First, though, I will direct you to Michael Hagedorn’s blog Crataegus Bonsai for a different (and, you might say, more coherent and concise) voice. His moss recipe should work […]

  3. […] be why they started putting moss on the soil. (See the moss posts mine and Michael Hagedorn’s link) #6 availability Unless you are in Japan, akadama is not readily available unless you go to a high […]

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