I heard another theory about dying roots: phenols.

Phenolic compounds are often secreted by stressed plants as a defense
against perceived outsiders - fungi, bacteria, viruses and even other plants
intruding on their territory. Unfortunately, those phenols are toxic to the
roots of the plant emitting them, not just the "outsiders".

In a suffocating or decomposing environment, the plants emit phenolic
compounds in an effort to save themselves, but being the sluggards we
growers are, we wait too long to fix the problem and the plants poison
themselves. Those dark brown to black roots are stained with the phenols.

True or untrue, I have been told that charcoal is specifically added to
flasking media to absorb those compounds, so the seedlings don't kill each
other.

--

Ray Barkalow - First Rays Orchids - www.firstrays.com
Plants, Supplies, Artwork, Books and Lots of Free Info!


"jtill" wrote in message
oups.com...
Carwashes have pits to catch mud and grime washed off cars. If you dig
them out the goop smells very bad and is black and green. Spread it in
the sun and in a short time it is again dirt, dirty dirt but dirt.
Anaerobic bacteria live in Oxygen free environments and give off H2S,
Hydrogen Sulfide gas which smells like rotten eggs. A very toxic
chemical and in those mud pits they live and eat up all grease and
such, good action!. I suspect that is what kills orchid roots, bad
action!, in rotten medium. I can't test that theory now "cause I ain't
got no rotten roots"! All my plants are in S/H, leaving no room for
these little ABs to live and grow. Next time you have rotten roots lay
them out in the sun, the smell and color will leave.
Joe T