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Vermiculite, like other layered mica products, is expanded by heating,
which drives off the crystalline-bound water that bonds the layers
together. With exposure to an outside source of water, the layers will
eventually collapse and rebond, rending it useless.
Ray Barkalow - First Rays Orchids - www.firstrays.comPlants, Supplies,
Artwork, Books and Lots of Free Info!
----- Original Message -----
Sent: Friday, November 18, 2005 9:12
AM
Subject: [OGD] Vermiculite
The following is from our soon to be released Timber Press
edition, "Orchid
Species Culture...Oncidium/Odontoglossum Alliance." It
should be noted that
there have been reports of dangers from asbestos
contamination in using this
product, but a Google search revealed that EPA
tests show that dangers to
consumers are minimal. As with the use of all
dry, powdery products,
however, one is probably safer if a paper mask is
used during the mixing
process.
"Vermiculite is an expanded mica
that holds tremendous quantities of water
for long periods of time. It has
a neutral pH of 6.5-7.2, is light and
sterile, and contains a high level of
magnesium and potassium. It can be a
beneficial addition to terrestrial
mixes for plants which live in bogs,
experience flooding, or require
constant moisture. It stays too wet,
however, to be suitable for use with
most epiphytic orchids. Fertilizer
should be decreased if vermiculite is
used, since this medium absorbs large
quantities of nutrients whenever
fertilizer is applied. Small quantities of
vermiculite in seedling mixes
could help prevent the media from drying out.
Horticultural-grade
vermiculite should be used since other grades may be
excessively
alkaline."
I hope this helps answer the
question.
Cheers,
Charlie
_______________________________________________
the
OrchidGuide Digest (OGD)
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