was Growing nerines, now clay versus plastic pots

gentian21 gentian21@comcast.net
Tue, 04 Oct 2011 10:02:03 PDT
I agree.  I thought that was the traditional understanding of pots unless 
you are growing under cover,
or in a climate that you never experiences excessive wet periods.
My take of roots clinging to a clay pot is because they are seeking air not 
water.  That is the driest place.  Of course if you are using clay pots you 
are watering more often and the center of the pot has more moisture.  Plants 
that want to cling their roots to rocks will cling them to a clay pot. 
Agaves love to grow that way.  Plastic is for if you want steady moisture 
which is logical for most plants if you are growing them in an arid 
environment. But many plants want to dry out completely after watering (not 
wet overnight).  If you have had to put up with rains every couple of days 
you want it to dry off in a few hours. The refrigerating effect is like the 
effect of troughs in that plants that really need water for cooling that 
would die from heat alone would rot if watered in the heat but can be 
watered in the heat.  Perhaps this only applies in humid climates.  The idea 
that plants can rot in clay pots can only be if the pots are sit directly on 
the ground so that the drainage hole gets blocked and worms can even get 
into the pot.  I hope they are not referring to glazed pots.  I have heard 
people say that hypertufa is not porous and does not have surface 
evaporation for them.  When making troughs you have to make sure to brush 
the inside of the trough with a wire brush to remove the layer of cement 
that has formed from the surface water unless you have used a porous 
material for the mold.
Frank Cooper
zone 5b
central Illinois

-----Original Message----- 
From: Peter Taggart
Sent: Tuesday, October 04, 2011 2:43 AM
To: Pacific Bulb Society
Subject: Re: [pbs] was Growing nerines, now clay versus plastic pots

I am amazed at the lack of insight into clay pot management. Our pots are
simply tools and as a carpenter may use a spoke shave for one job, he my use
a plane for another.
When I dig up potatoes I use a fork and when I mix compost I use a shovel.

A small clay pot holding a Hippeastrum or Gesneriad, standing on a
windowsill, will dry out very quickly,- so for that I use a plastic pot.
A large clay pot holding Haemanthus albifloss in clay soil, standing on a
windowsill drys slowly and is impossible to saturate, so I use a clay pot to
ensure that it doesn't rot, - plastic would be fine if it were never over
Out side I have a couple of thousand pots of assorted bulbs under glass and
in open plunges. The quickest way to kill a winter growing bulb is to water
it in a black plastic pot and leave the pot exposed to hot sun. The roots
and bulb will cook.

Properly plunged clay will behave as part of the plunge medium with an even
moisture air and nutrient flow throughout the plunge. I find this very
useful for bulbs adapted to hot dry conditions where the roots and / or
bulbs are deep down where they stay cool and moister.
On the scale of individual pots this hot surface and cool base can be
achieved with plastic long toms packed together, as Alberto describes and no
doubt Nick is achieving.

It is apparent that several people have learned how to use plastic and
failed to learn how to use clay. Their failures with clay are because they
don't use clay pots in a way that suits their own conditions and maintenance
regime. It really doesn't matter so long as their plants grow well in the
regime and pots they use. I use both to good effect, and have enough
experience to know that clay pots also have useful qualities.

The "refrigerating effect" Alberto refers to is very desirable for a lot of
bulbs I grow which go dormant when too hot. Before or after a hot day in
late autumn or spring, spraying to cool the plants down will help to
maintain growth and stop premature dormancy.
I think of this as a replacement for early morning dew, or mist, It is not a
drenching and should never be done in hot sun.
Peter (UK)

On Tue, Oct 4, 2011 at 4:29 AM, Alberto Castillo

> It is refreshing to see such an authority as Nick de Rothschild bring some
> reality to this incredibly traditional view.
> The worst effect of clay pots to certain bulbs is the refrigerating 
> effect:
> it cools down when watered and heats as mix dries.
> This is a long list but I grow my bulb collection (and allied plants)
> comprising thousands of them, all in plastic. Not a single one in clay and
> all do perfectly well. Of course the mix in them is very well drained and
> most important drainage holes are carefully cut.
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