Mosses

Mosses are small flowerless plants that typically grow in dense green clumps or mats, often in damp or shady locations. ... Mosses do not have seeds and after fertilisation develop sporophytes with unbranched stalks topped with single capsules containing spores.

They are typically 0.2–10 cm (0.1–3.9 in) tall, though some species are much larger.

Mosses are commonly confused with lichens, hornworts, and liverworts. Lichens may superficially look like mosses, and have common names that include the word "moss" (e.g., "reindeer moss" or "iceland moss”)

The moss life-cycle starts with spores that germinates to produce a either a mass of thread-like filaments or flat and thallus-like. Massed moss protonemata, a thread-like chain of cells that forms the earliest stage in the life cycle of mosses and liverworts and typically look like a thin green felt, and may grow on damp soil, tree bark, rocks, concrete, or almost any other reasonably stable surface. This is a transitory stage in the life of a moss, but from the protonema grows the gametophore ("gamete-bearer") that is structurally differentiated into stems and leaves.

 Habitat

Habitat

Dense moss colonies in a cool coastal forest
Moss with sporophytes on brick
A closeup of moss on a rock
Young sporophytes of the common moss Tortula muralis (wall screw-moss)
Retaining wall covered in moss
A small clump of moss.

Moss requires enough sunlight to perform photosynthesis. Shade tolerance varies by species, just as it does with higher plants. In most areas, mosses grow chiefly in areas of dampness and shade, such as wooded areas and at the edges of streams; but they can grow anywhere in cool damp cloudy climates, and some species are adapted to sunny, seasonally dry areas like alpine rocks or stabilised sand dunes.

Substrate

Choice of substrate varies by species as well. Moss species can be classed as growing on:
Rocks
Exposed mineral soil
Disturbed soils
Acid soil
Calcareous soil
Cliff seeps
Waterfall spray areas,
Streamsides
Shaded humusy soil
Downed logs
Burnt stumps
Tree trunk bases
Upper tree trunks, and tree branches
Bogs.

Moss species growing on or under trees are often specific about the species of trees they grow on, such as preferring conifers to broadleaf trees, oaks to alders, or vice versa.
Mosses are never parasitic on the tree.

Mosses are also found in cracks between paving stones in damp city streets, and on roofs. Some species adapted to disturbed, sunny areas are well adapted to urban conditions and are commonly found in cities.

Wherever they occur, mosses require liquid water for at least part of the year to complete fertilisation. Many mosses can survive desiccation, sometimes for months, returning to life within a few hours of rehydration.

It is generally believed that in northern latitudes, the north side of trees and rocks will generally have more luxuriant moss growth on average than other sides. This is assumed to be because the sun on the south side creates a dry environment.

Moss-cyanobacteria relationship

In boreal forests, some species of moss play an important role in providing nitrogen for the ecosystem due to their relationship with nitrogen-fixing cyanobacteria. Cyanobacteria colonizes moss and receives shelter in return for providing fixed nitrogen. Moss releases the fixed nitrogen, along with other nutrients, into the soil "upon disturbances like drying-rewetting and fire events," making it available throughout the ecosystem.

Moss collections are quite often begun using samples transplanted from the wild in a water-retaining bag. However, specific species of moss can be extremely difficult to maintain away from their natural sites with their unique requirements of combinations of light, humidity, substrate chemistry, shelter from wind, etc.

Moss and its use in Bonsai

For our use in Bonsai we must take into account the area where the moss is collected and where the substrate and humidity are a good match for type and soil mix of our bonsai to be planted. It will be noted that when Bonsai are seen at shows that moss has been transplanted, often with may varieties across the surface of the pot. This may look attractive to the eye and for the duration of the show but will inevitably result in the lost of all the moss within matter of weeks.

Growing moss from spores is even less controlled. Moss spores fall in a constant rain on exposed surfaces; those surfaces which are hospitable to a certain species of moss will typically be colonised by that moss within a few years of exposure to wind and rain. Materials which are porous and moisture retentive, such as brick, wood, and certain coarse concrete mixtures are hospitable to moss. Surfaces can also be prepared with acidic substances, including buttermilk, yogurt, urine, and gently puréed mixtures of moss samples, water and ericaceous compost.

The above method can work extremely effectively and the best course of action is to remove some of the naturally occurring moss on our Bonsai soil when spores are being produced (is very effective) and using this as the “seeding” process for our own cultivation, making a note of the soil mix and bonsai type the moss was naturally occurring on.

It should be noted that trays of mixed moss types that have been collected from woods, bogs or stone areas may work on only specific cultures and probably will die due to the conditions they are moved to.

Moss spores

Moss spores can be purchased for use with Bonsai from Willowbog Bonsai
http://www.willowbog-bonsai.co.uk/store/moss-spores.html

“Our Moss Spores are of a variety commonly termed 'Kyoto' Moss, as is prevalent at the Kyoto Gardens in Japan. The beautiful, bright green velvet appearance is weed free, since it is greenhouse-grown in sterilized soil. Shelf life is indefinite, as spores are packed in a zip-lock bag within the envelope. A detailed growing guide is included.
Covers up to 3 square feet.”

Inhibiting moss growth

Vigorous moss growth can inhibit seedling emergence and penetration of water and fertiliser to the plant roots.

Moss growth can be inhibited by a number of methods:

Decreasing availability of water through drainage.
Increasing direct sunlight.
Increasing number and resources available for competitive plants like grasses.
Increasing the soil pH with the application of lime.
Manually disturbing the moss bed
Application of chemicals such as ferrous sulphate (e.g. in lawns) or bleach (e.g. on solid surfaces).

The application of products containing ferrous sulphate or ferrous ammonium sulphate will kill moss; these ingredients are typically in commercial moss control products and fertilisers. Sulphur and Iron are essential nutrients for some competing plants like grasses. Killing moss will not prevent regrowth unless conditions favourable to their growth are changed.

The growth of Moss onto our Bonsai Nebari and bark of pines can be damaging as the bark softens and rots due to the large water retention of the moss.

As can be seen from our notes above the pH is critical to the moss so a very effective way of clearing the moss from Bark is with a localised wash of Vinegar, ordinary Vinegar is painted on the areas to be killed.

Vinegar is also a good method of killing the algae on branches and particularly on clogged Juniper leaves. A solution of 10% has been found to be affective.

Further reading

Further reading can be found in this useful pdf.
http://rbg-web2.rbge.org.uk/bbs/resources/fletcher.pdf

This article was adapted from article from wikipedia with Bonsai specific information added.

Young sporophytes of the common moss Tortula muralis (wall screw-moss)
Red moss capsules, a winter native of the Yorkshire Dales moorland