by George Buehler

Lee Squires recently sent an email advising me to check out a web site on moss (www.mossacres.com). This site is operated by a commercial supplier of four types of moss and is located in Northeast Pennsylvania. It appears that three types of moss they offer could be used in bonsai. However, they supply living moss and generally sell in large quantities (square feet quantities). If you're looking for moss for large areas (i.e. rock gardens, etc.), this might be the web site to visit. For smaller quantities, personal collecting is probably the best bet.

Mossacres does have several technical sections on moss, mainly related to the four types of moss they sell. In reading through this information, I realized that I really didn't know too much about the way moss grows, its nutrient needs or the best way to keep it healthy in our bonsai. I started my search for more information and decided that what I found would make a good article for the newsletter. I found several interesting articles on moss on the BonsaiTalk forum and requested permission of the author (Will Heath) to reproduce it here. As I went over the article, I decided that although the information was accurate, a number of areas would benefit from additional information and clarification. I am using the general layout of Mr. Heath's article (with permission) plus additional referenced information.

Moss is a type of simple or nonvascular plant (i.e. Non-vascular plants are plants that lack water-conducting vessels in their tissue). Mosses belong to the class Musci, in the division (or phylum) Bryophyta. There are seven subclasses of mosses1. If you really want to learn more about the various subclasses, you can visit the referenced web site.

Mosses are mostly one cell thick, have no true roots (they have rhizoids instead of true roots), and have no stems, flowers, or fruit. Instead of seeds they produce spores for reproduction. That is about as technical as we will get.

Mosses spread in multiple ways, but unlike flowering plants, they depend on moisture to reproduce. Mosses reproduce by spores, which are analogous to the flowering plant's seed; however, moss spores are single celled and more primitive than seeds. Spores are housed in the brown capsule that sits on the seta (see Figure 1). As the spores ripen, they are dispersed from the capsule; and some land in areas where there is enough moisture for them to grow. The young moss looks like a very thin tangled mass of branching green hairs. Buds will appear next on the green hairs, from which tiny stalks and slim ‘leaves' will grow2.

Other plants that are not related to moss, but share the name "moss" includes club moss, flowering moss, carrageen, reindeer moss, and Spanish moss. The Japanese have gardened with moss for centuries. Valued for its reduced need for watering, the greenness of moss is considered to add a feeling of lushness and serenity to Japanese gardens3.

HOW DO MOSSES ACQUIRE NUTRIENTS?

Mosses also have different mechanisms which they use for acquiring nutrients. Some mosses are able to take up nutrients from water flowing over them (ectohydric moss), thus they have very effective absorptive surfaces. Other mosses (endohydric moss), sequester nutrients directly from the soil or substrate on which they are growing and transfer the nutrients to their growing tips. Other mosses obtain their nutrients directly from the air.

With this in mind we can see that the physical and chemical nature of the substrate as well as its water holding capacity, is extremely important in establishment of mosses. In general mosses grow best on poor quality soil (even stones) and don't need additional fertilization. A mild solution of an acid fertilizer seems to help (see below) but is not necessary. The only necessary application to mosses is water – the more the better.

While we are on nutrients, there are some things that must be avoided to ensure good moss growth. There are several ‘moss killers' on the market today. These are designed to rid people's roofs, lawns, and sidewalks of moss. I found the contents of several on the web. Although not all of the items listed next are found in each of the products, a general theme is evident: iron, zinc sulfate, copper sulfate and bleach. I remember reading an article about cleaning your pots (while the tree was still in the pot) with bleach. If you had moss on it, I believe it would be killed (or at least hurt) by the bleach application. I use soluble iron periodically when I fertilize my trees. In looking back, I remember that after using this, the moss in my pots seemed to lose its bright green color. I wonder now if it was from the iron in the fertilizer. A number of people use Superthrive in conjunction with a fertilizer. Superthrive does contain iron, zinc and other micronutrients. However, since it is in such small concentrations, it probably doesn't affect the moss very much. A suggestion is in order: if you use iron, Superthrive, or similar fertilizer additives, it probably would be a good idea to avoid wetting the moss on your bonsai soil with these materials. Instead pour it over the bare bonsai soil.

GROWING MOSS

First off, it must be stated that the city of Louisville water supply has an average pH (a measure of acidity/basicity) of about 8.34 [neutral is 7.0; 8.3 is basic]. The ideal range for growing moss is 5.0 – 6.0. Somewhat lower readings are fine, but anything over 6.5 should be adjusted with MirAcid or Aluminum Sulfate. If you are starting a moss bed, you do not have to wait following soil amendment prior to transplanting, just be sure to water the chemicals in well so that they are not pooling on the surface. I have also found that misting the moss with a dilute solution of MirAcid during the growing season seemed to help the growth. This may be because it is acidifying the basic water or soil.

TRANSPLANTING MOSS

Moss transplanting can be performed year-round. However, the most ideal times of the year are spring (Late March through mid-June) and fall (September through November). It should be noted that although the hot summer months are not ideal, it can be done then if adequate moisture is available.

GROWING MOSS

There are several methods to grow moss. I will list four methods: plug growth, dry spore/moss dust, paste method, and tray method.

1. Plug growth

Small pieces of moss are put into a shallow container (such as a plastic grow tray) which has been filled with sand or ordinary garden soil. The moss pieces are placed in irregular pattern in the tray, watered well and placed in a semi sunny area. Daily misting is required. Within a short time, the tray will be covered with moss. An alternative way is to use larger sections of moss, as we use on our bonsai, and place them in a large plastic grow tray. I found however, using this method seems to keep the moss green but it doesn't spread as fast as the smaller pieces.

2. Dry spore/moss dust

Commercial spore can be purchased (i.e. Kyoto moss) from several sources. Additionally, moss can be collected, allowed to dry and minced into a fine dust. This fine dust or commercial moss spores can be sprinkled over a tray containing sand or garden soil, watered gently, and misted daily. Within about a month, you should see a light green color over the top of the soil indicating the moss is growing. The dust can be sprinkled over your bonsai soil, but the results are generally poor since the daily watering of the bonsai causes the spore to wash down into the bonsai pot.

3. Pasting it

The moss is collected and allowed to dry slightly. It is then added to a blender dedicated to this use only, and beer, buttermilk or water is added and blended until a paste with the consistency of mortar is formed. It is then placed on a brick which is in a water filled tray without drainage holes. The brick acts like a wick constantly drawing water up. The paste is spread on top of the brick and misted daily. This technique will allow you to take perfect sheets off of the brick easily, whenever you need them.

The paste can also be used on rocks in shade gardens; the moss will grow as long as it is keep moist. I have seen garden benches, walls, and statues covered and decorated with moss using this technique.

4. Traying it

A shallow container which has small drainage holes is filled with an inch of fines or sand misted until it is damp. The moss is minced very fine with a razor blade and then sprinkled evenly on the surface of the sand or fines. It is then misted again and put in a dappled shade spot, being sure that the top never completely dries out. It will usually require misting once a day. In two weeks' time, the entire surface will be green; and shortly thereafter, you will have a perfect sheet of moss. The moss can be grown in its original container for over a year and it is a handy way to keep moss ready. The main draw back is that the sheet is always some what uneven. However if you are using pieces when applying, that is not a big problem.

THINGS TO LOOK FOR WHEN HARVESTING MOSS FOR BONSAI

• Varied types growing together.
• Differing heights, textures and colors.
• Stay away from the long hair types. These grow very fast and will take over a pot very fast. They grow up the trunk and can cause rot.
• Look for the stuff that looks like the old tomato pin cushion your mom used to use. It should look like green velvet, something you would like to walk on bare footed. Then there is the sort of grey colored moss, it sort of looks like lichen.
• Look for it in parking lots of commercial buildings. They sometimes have large patches of bare ground with all sorts of moss growing. It can be lifted with a kitchen utensil used to ice cakes, a putty knife or similar utensil.
• Moss can also be found in wooded areas or areas that stay routinely moist.

A word of caution when collecting moss: depending on where the moss is collected, it may contain residue of pesticides, fungicides, herbicides or other harmful chemicals due to it just being there when applications are made. Some of these chemicals may be harmful to your bonsai trees. When this collection method is used, it is a good idea to put the collected moss in a separate container and allow it to acclimate to your area for about a month. With the daily misting of the moss, most of the chemicals are washed away.

There are advantages to cultivating your own moss. When you cultivate, you can have a number of different types of moss always available to you, and you control the size pieces you use. A major advantage of this is that you can use a few different types of moss in the same bonsai, giving the illusion of different plants growing under the tree having multiple textures, This allows for more creativity than a single species.

USING MOSS IN BONSAI

We as bonsai artists use moss to add a dimension to our bonsai that helps with the overall visual illusion. We put it onto the soil surface to give the illusion of grass, plants, and such, growing in scale under the tree. This benefit however is often negated by the fact that moss, if allowed, will make a shield on the surface that water will not penetrate. It can also create a barrier, trapping in moisture and not allowing the soil to dry out. This is the reason that most people will recommend that moss be applied only to the surface of the soil a few weeks before showing the bonsai and removed immediately afterwards.

Moss can be left on your soil year around, if some simple precautions are taken. Always leave spaces between the pieces to allow for water penetration and evaporation. Never butt up the pieces tightly. A good rule is to cover no more than 75% of the soil surface with moss. Try also not to run the moss right up to the pot's edge, leaving the rim area free while ending the moss naturally at this point will look much better.

Be careful with pines and most conifers, as most are dry loving trees. If your moss on these is green and healthy, chances are that you are watering too much. I have had some success keeping healthy moss on a Scots Pine by watering as normal but also lightly misting the moss on a daily basis. Vance Wood keeps his "Silver Moss" growing on the soil of his award-winning Mugho Pine year around. Mughos do like a little wetter soil than most pines, which could be the reason for his success.

References:

1 What is Moss – www.whatis.tv/moss.html

2 Basic Moss Biology, Oregon State University "Living With Mosses"

3 Moss 101/102 – BonsaiTalk Article – Will Heath

4 Annual Water Quality Report; Louisville Water Company; 2005

5 MossAcres technical report, www.mossacres.com

6 Moss – BonsaiTalk Article - Al Keppler