Orchid Growing Substrates

- There is one interesting exercise, not pertaining at all to Paphiopedilum. A lot of species need
extremely wet conditions, like sphagnum moss provides. Amongst them, dendrobium jacobsonii,
dendrobium cuthbertsonii, brevicaule, a lot of the oxyglossum species, some anoectochilus… They
need neutral to sometimes alkaline conditions (dendrobium jacobsonii is covered with highly alkaline
ashes from the volcano nearby). The secret to grow them is to grow them very wet but with
something to raise the pH, otherwise they suffer and die. That’s why many growers need to keep
those species and some others, either ‘very dry in sphagnum moss or barely moist’ and periodically
loose them. One good way to pot such plants, which include a lot of strange orchid species from
Papua New Guinea is to pot them in New Zealand sphagnum moss, and add a top dressing of calcite
or aragonite sand. Prior to that, Xavier used sand made out of limestone, which is working really well,
but not always available. This way of making very hard to grow species alive and expanding like
beginner’s plants cannot be done with Chile sphagnum moss, as the addition of lime based
compounds will raise the EC, and decompose the Chile sphagnum moss, which will result eventually
first in a spike in salinity at the roots, followed by a sharp drop of the pH, as a result of the
decomposition.
- Maudiae types Paphiopedilum have some ancestors growing in sphagnum moss in the wild, like
Paphiopedilum lawrenceanum and some strains of callosum, which actually grow in sphagnum bogs.
Maudiae types are easy to grow in New Zealand sphagnum moss, providing they are not kept too wet.
Though, with some other species incorporated in the ancestry, some will prefer another mix, but
some growers produce dozens of thousands of Maudiae Paphiopedilum in New Zealand Sphagnum
moss, with great success. However, after some years there can be acidity related problems, which can
justify the use of another potting mix.
For commercial growers, sphagnum platelets can be used for deflasking. One seedling, one dry platelet on
each side and then is placed in a tray. After watering, the platelets expand, and form what is called a plug,
with the seedling in the middle.
Sphagnum comes as well in powdered form - Petals, it is primarily used in this stage as an additive to
potting mixes. For a standalone product, fibers are preferred, ranging from 10cm up to 30cm, sometimes
50cm. The fashion in Japan is to use exceedingly long fibers, though it is very unclear if it has any benefit
other than aesthetic. The basic product is still the same. To pot Paphioepdilum using only New Zealand
sphagnum moss, a grade of 5-15 cm approximately is preferred. The way to pot plants as a standalone in
Sphagnum moss is very important. The fibers are placed in rows, the plant is placed in the hand, and the
sphagnum is placed in careful lines, parallel to the plant growth. When enough has been placed, in order
to have the sphagnum fibers vertical in the pot rather than all mixed, the whole root ball and fibers are
pressed slightly, and inserted in the pot. The whole ball is forced a bit in the pot, to flatten the bottom.
Then the top of the pot is leveled by hand, to make a uniform, flat surface. However, the fibers being
vertical, it improves greatly the drainage of the plants and they will grow better this way.
Sphagnum has antiseptic properties; however those have never been studied extensively. It seems a fair
part is washed out over time, or degraded, but at least the New Zealand sphagnum moss seems to retain
those properties for longer time. One of the antiseptics identified is an organo-zinc compound, but little
more is known today. Sphagnum as well contains high levels of calcium and magnesium, under an
insoluble form, but it appears that nevertheless it is made available to the plant slowly over time. It must
be noted that some Sphagnum from Chile had unacceptable levels of sodium as well. In fact, according to
more recent studies, Sphagnum is able to exchange cations, potassium, sodium, calcium magnesium, with
Xavier Garreau de Loubresse
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