Date: Thu, 30 May 1996 00:44:46 -0400
From: Pine Ridge Orchids <pinerdge@gil.net>
Subject: [8841] Rockwool culture

     I have been using rock wool for over 12 years. Our primary commercial
crop is Phalaenopsis, with a secondary crop of Paphiopedilums and
Phragmipediums. I have also used the various rock wool mixes on Catts, Dens,
Orchids, Phaius, Angraecoids, etc.
     I first started investigating rock wool as a media component when it
became clear that there would be problems in the future in obtaining both
quantities and quality of the natural medias such as tree fern, fir bark,
and good sphagnum. I tried looking into inorganics as a substitute. I had to
find a product that was uniform in quality year to year and would be
available - I really didn't want to start to produce 100,000 Phals and Paphs
a year in one media just to find out that the next time I needed to order a
truck load of material that it was not available because the was guerilla
warfare in the hills of Guatemala or the New Zealand sphagnum bogs were
being depleted. Cost factors and our own experiences of battling bush snail
populations in sphagnum from Chile also factored into looking into inorganic
medias. This is well before Grodania started to export to the US. At the
time, the only rockwook products available were water absorbent material
based on iron slag - yes it actually started to rust over time and released
vast quantities of iron oxides.
     Eventually, Grodan was available in the US with exports of water
absorbant from Denmark and water repellant from Holland. I have always
utilized the largest grade of rockwool - the European formulations had long
(upwards of 3"-4") fibers. As time went on and I became more and more
comfortable with the mixes, Grodan, of course, had to change things. The
North American manufacturing plant was built in Canada and the fiber size
was drastically reduced - the coarsest today is actually slightly smaller
than the European medium grade - and we use a rockwool blower that actually
seperates each fiber from the compacted bale thus giving us an almost 25%
increase in volume over hand enpanded media. The water repellant
manufacturing process was improved at the same time - the European media was
made repellant by applying a binder to the ouside of the absorbant material
- this would actually over a period of 6 - 8 months dissolve off and I would
be left with a pot of water absorbant media - not what I wanted in the long
run. The repellant from Canada is, from my understanding, totally it's own
material and is repellant throughout. I have repotted multi-floral Paphs
after 2 - 3 years in this media and the repellant is still repellant.
     Every grower has his/her own way of growing and watering and
environments vary drastically all over the world. I have found rockwool, in
our conditions, to be very forgiving. I basically have two media mixes - one
for potted Phals and Paphs that holds a bit more water by having a higher
percentage of absorbant, and one mix for seedling trays that holds less
water because, as is well known in Bonsai, the shallower the container, the
more water it holds - this would be the media I have used on Catts. The
rockwool is broken up with the addition of sponge rock (very large sized
perlite), aerolite (bean bag pellets of styrofoam), and some organic
material. This material the last three years has progressed from Servo
(baygas - composted sugar cane) to various peat-lite mixes and now to coir
(composted coconut husk fiber). The Servo decomposed too quickly on a
commercial basis; the peat-lite mixes grew a tremendous crop of fern
seedlings constantly (these I believe were in the peat mixes because it was
just too uniform to be air distributed spores); and now the coir seems to be
doing an interestingly good job. It's an interesting product - lignin
instead of peat's cellulose - I have talked to Florida rose growers who have
dug up 7 - 8 year old beds and they have said the coir is still like new. I
figure if that is true, the material may last 2 years in pots - which is
what I need.
     I look at speed of production (everything costs), quality of foliage,
and quality/quantity of roots to determine how the plants are doing overall.
It will take at least a full year, even under South Florida conditions where
we get Phals to bloom in less than 6 months out of flask, to determine how a
new media change is affecting the plants. I am constantly running media
experiments because I don't believe there will ever be a 100% ideal potting
media - this seems to be working pretty well for us right now. Hope this has
been of some help to you all --  Terry A. Glancy



From GERRARD@FCRFV2.NCIFCRF.GOV Sat Mar 23 09:59:40 1996
To: ahicks@mailhost.NMT.EDU
Subject: rockwool

I asked from some input on rockwool on OLD some months ago and got little
reply.  However since then I do have some experience using it and offer
the following comments for what they are worth.  Most of my serious
collection is composed of Pleurothallids grown in a homemade Wardian
case under HID lights in an airconditioned basement.  Other more robust
plants are windowsilled throughout the house and I even have some terete
leaved things at my lab window at work. My interest in rockwool was
promted by the fact that most pleurs require repotting every year
(the practice of the successful growers that I know).  The reasoning
was that since RW is inert there would be no breakdown stuff and the
annual repotting would be eliminated, provided one avoided salt build
up.  I tried a few plants in RW plus some perlite and crocked the pots
with styrofoam peanuts for drainage and aerations.  Since the case has
high humidity (another pleur. requiremnet) I used clay pots.  Water has
been rainwater or condensate from the central AC when that is in oper-
ation.  The initial trial looked good and I subsequently repotted
everything in RW.  To date all seems well.  The negative feature is the
growth of green or black slime crud on the top of the media.  Some pots
are now getting a moss growth which is aesthetically acceptable.  One
can justremove the offending layer and add more.  I also repotted my
windowsill stuff in RW, using plastic pots since the air is much dryer
in the house.  These seem satisfactory too.  The lab plants have an
even drier and warmer envirom=nment but are doing well, especially
since there is deionized water on tap. All in all I think it has merit.
Despite some comment I read on OLD, there are no insects living in this
stuff, including fungus gnats in my experience.  I have had them all!
Hope that this is helpful.  Bernard C. Gerrard, Frederick, MD.