There are four ways I use stones
for potting. The most common is as a
layer on the bottom of the pot, to provide weight to make the pot more stable for
orchids that produce towering, heavy inflorescences that dwarf the plant and
can easily overturn it. This also helps
ensure that the mix drains well.
Sometimes I use them in the pot
to have something to hold the orchid fixed in place. I usually do this when using coarse potting
media that initially provides little stability to the plant. In this case I tie the plant to a stone and
place the stone into the mix. “A wobbly plant
is a dead plant” as my friend Jose Oliveras uses to say. The stone provides the plant with a firm
anchor until its roots can get a grip on the media.
In rare cases, I use it as potting media for
particular plants that are very intolerant of any potting media that when it
decays starts retaining too much water or that can be turned into slush by
insects bacteria or fungi and will smother the roots by creating areas that
impede the flow of air.
In the case of the Encyclia alata in the photo,
the orchid is growing in side of a wire basket that has a two-inch layer of
pebbles inside. As you can se the plant
has been growing for a while in the basket, slowly increasing in size. The younger pseudobulbs are not in contact
with the media, they are about two inches over it. The roots grow toward the basket and eventually
enter the media.
On occasion I have used stones to hold the orchid
in an empty pot. In these cases, the
plants are attached to a single stone and there is no media in the pot. I do this with plants that produce larger,
stronger root systems if the roots are allowed to grow with no media to confine
them. I used to grow Cattleya Jose Marty
“Mother’s Favorite” in this way.
Using stones as a potting media has the
disadvantage that they are heavy. The
wire basket in which Enc alata is growing weights quite a bit. However, the heavy weight has its benefits. This Enc alata can produce a four feet tall
inflorescence, with dozens of flowers.
The weight of the stones helps balance the weight of the inflorescence.
Because stones don’t decay, you
have to provide the plant with a balanced fertilizer. During
the growing season you have to really make sure this plant is fertilized
regularly or the plant will produce smaller pseudobulbs that it could. Stones are not water retentive, so the plant
has to be watered often when during its active growth phase.
Compared with the other media I
use, stones are a very minor component of my orchid growing. But they can be useful in particular cases
for plants that have specific needs. I prefer to use smooth river pebbles. On one or two cases I have used them to cover
fibrous potting material to stop birds from stealing it.
A final note, don’t just grab
any old stone and stick it in a pot. I prefer
to use volcanic rock because they tend to be chemically inert. Some stones will react with the acids in the
media and alter the pH of the mix, some plants like this, others don’t. Never use stones that are crumbly or might
leach unwanted chemicals into the mix.