These compounds (polyacrylamide and polyacrylate polymers) go by
the generic name "superabsorbent polymers," or SAPs. They can hold several
hundred times their own weight in water. The ones featured are probably
the potassium polyacrylate polyacrylamide copolymer.

Their purposes include everything from "pigs" used in firefighting
to absorb spills, the packing in diapers (tear one apart and look for the
hard, grainy crystals), magic tricks, and some agricultural purposes that
crop up every couple of years or so.

While they may have certain limited applications in agriculture,
their use with orchids is minimal. These cystals expand and contract as
they absorb or release water, so they shrink and grow. The net upshot is
that anything that does so will eventually wash out of your bark media and
onto your greenhouse floor (don't slip on 'em). For epiphytic species that
require lots of air circulation, this renders them useless. Even if they
could be retained within the media, epiphytic orchids generally die from
too much water, rather than not enough. SAPs in this context would prove
to be counterproductive.

In the other application (terrestrial plants), they would retain
too much water. There are plenty of other non-synthetic compounds that are
capable of doing the exact same thing for a whole lot less money and
trouble.

It is worth noting that the markup on these products is huge; they
can be purchased on an industrial scale for tens of dollars per hundred
pounds. Then they're re-packaged for everything from watering crickets for
the pet trade to fancy flower-holding materials at the crafts store for a
few bucks per ounce. They aren't toxic in the polymer form, but the
monomer (acrylamide) is nasty stuff; I'm not sure that the breakdown of
these compounds in a confined, organic (reads: greenhouse) setting has
been well-explored.

As an aside, I tried them as substitute gelling agents for plants
_in vitro_. Although I won't discount the possibility that the autoclaving
changed them somehow, 6 permutations I tried killed orchids dead. Another
two were *almost* useful, but didn't compare well at all to the control
(agar).

I just don't see the upside to using SAPs with orchids. If anyone
has one that can beat (pound per pound) stuff like sphagnum, I'd sure like
to hear it.

The e-mail address in the header is a spam trap. Send no mail
there.

Cheers,

-AJHicks
Chandler, AZ