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A type of light-coloured
porous volcanic rock,
commonly used as an additive in
potting mixes |
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Pumice is a frothy
volcanic rock formed by the expansion of gas in erupting lava.
Commonly perceived as lumps or fragments of pea size and larger
but can also occur abundantly as ash-size particles. Because of
its numerous gas bubbles, pumice commonly floats on water.
Pumice is an extremely
porous and light-weight component of
potting medias.
Succulent growers frequently use pumice grit as an additive
in potting mixes to create excellent
drainage
conditions for the plants. Although the pumice grit may be
substituted by various mixtures and additives (e.g.
perlite,
vermiculite)
the opinion of most cactus growers seems to be that pumice,
where available, is the best aggregate to use as a basis for a
good
cactus and succulent mix, because it is loose and friable
with lots of available space for
air and
roots. It
drains very quickly, leaving air space while still retaining
enough
moisture to reduce frequency of
watering
without danger of
root hair
loss.. It is used in variable percentage and usually a potting
soils for cactus contain at least 25-50% pumice, but plants
demonstrated to grow also very well in a 100% pumice grit
medium, with or without a small percentage (3-5%) of loamy soil
or humus. This is particularly indicated for difficult species
particularly
sensitive to
root rot. |
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