On 24 Nov 2004 at 19:12, Theo wrote:

But this is a sort of (with)out-of-soil-growing !

Oh, phoo! You've heard of "safe sex?" We're practicing "Safe
Bonsai growing."

When you add dirt you cannot avoid adding pathogens (unless, of
course, you sterilize the dirt, and I know you don't) and, like
casual sexual partners and STD, while chances are fairly good
that the pathogen you add will NOT hurt your tree, there is the
chance that it will.

As for compost, GOOD compost is self-sterilized. It gets HOT in
a good, well-turned compost pile. Still, compost is pretty fine-
grained soil and since it is the product of decay so by
definition if it has decay bacteria included in it, your compost
will only get finer as time goes on. That clogs up your soil.

It is often forgotten, but roots need more than water and
nutrients. They need air. Clogged soil interferes with the
provision of air to the roots.

Over time, the pine bark we use decomposes bit and actually
becomes a kind of soil in our pot. About then, though, we
repot.

Jim Lewis - - Tallahassee, FL - Nature
encourages no looseness, pardons no errors. Ralph Waldo Emerson



Nina Shishkoff wrote:

Anil said:

I have not been able to understand why you people do not add natural

soil to the Bonsai compost!

There are 3 reasons for this:

1) Bonsai need well-drained conditions above almost everything else,
and the kind of non-soil mix we use gives very good drainage. There
is almost no way to add soil to a gravel-based potting medium without
clogging the air pores.

2) Most of our information on container-growth of plants comes from
the nursery industry, and in the US essentially no one uses soil in
their container mixes. I just did a survey of what the major
Rhododendron growers in the US use for their potting mix, and they all
use nonsoil mixes (and their mixes are essentially the same except for
the source of bark, which varies regionally). Since full-spectrum
fertilizers are readily available, there is no need for a soil
component in commercial nurseries.


3) Nonsoil mixes start out with few pathogens, and with a few
precautions, can stay disease-free. Mixes that use soil have to be
sterilized, and autoclaving soil changes its properties.

A few years ago I was involved in a survey of the Pythium flora in
greenhouses in the East coast (Pythium is the organism that causes
"damping off" and many root rots) and the results of our survey were
startlingly different from the results of scientists doing this sort
of work 40 years ago. The reason appears to be that most greenhouses
now use soilless mix and don't start their plants from seed as much,
preferring to buy flats from wholesalers. So the species of Pythium
in greenhouses today aren't coming in on soil; they're coming in on
the plants.

Nina, who uses no soil in her plant experiments, either.

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