Update on Permatill

[Jim McClements, Dover, DE z6]

A-Lrs

Last winter I reported that I seemed to be having excellent results using
Permatill (a granular substance made of fired slate, used primarily as an
additive to heavy clay soils) as a medium for growing arisaemas under lights
in their 2nd or 3rd growth cycles. I've been using it by itself, standing in
shallow water containing a dilute fertilizer solution, more or less in the
fashion of "hydroponics". It holds enough water to create a moist medium, yet
the particles are large enough to allow oxygen to easily permeate and avoid
anaerobic conditions.

At least, that's what I thought! Extensive use of the system over the past 10
months hasn't totally borne out my initial enthusiasm. It still works well
most of the time, but I'm seeing occasional pots where as many as half of the
tubers are rotted. I'm not sure why. It may be that I've gotten overconfident
and have had the standing water too deep at times. It may be that some
species are more prone to rot than others, although A. sikokianum (which I
always think of as a "rotter") has had no problems thus far.

I'm still going to use the system and let the pots get fairly dry before
adding more water to the flat, but I just wanted anyone who is trying this
method to know that it's not a panacea. And any suggestions, theories, etc.
would be welcome.

Jim McClements