"Martin Brown" wrote in message
...
In message , Franz Heymann
writes

"Mike Lyle" wrote in message
. com...

[snip]

I'd also guess (but it's only a guess) 40 cm is too big a pot:
best
way is the old rule of patiently going up one size at a time, and
only
when the roots have definitely reached the outside of the old
pot,
so
that any water you give will immediately go to the plant, rather
than
hang about going stagnant. (Some people, in this group notably
Franz,
ignore this rule without ill effect; but they have a watering
regime
to suit.)

That is an urban legend. If there were any truth in it, all plants
planted in the open ground, which is an infinite sized pot for
practical purposes, should fail.

That isn't true though. The ground has usually has pretty good
drainage.
A plant stuck in a pot has to rely on all the extra water escaping
from
a small hole in the bottom of the pot.

My pots all do have adequate drainage holes in the bottom, and I have
never noticed any waterlogging in them.
You are not addressing my point, which was that all this talk of
overpotting a small plant has no basis..

Block the hole and you have
stagnant water and few living things can tolerate HS (it is more
poisonous than HCN).

I was not discussing growing a plant in an undrained pot. {:-((
If you look back, you will see that my argument is concerned with the
old wives' tale that putting a small plant in too large a pot is bad
for it. I stick to my contention that that is nonsense.

I grow cacti and water them like normal house plants in mid-summer
but
they are planted in a very free draining grit with a small amount of
compost so they dry out between waterings.

That is good practice for growing cacti.. So how does that affect my
argument about the relative sizes of the plant and its pot?

I planted a very young Acer palmatum atropurpureum directly in a 45
cm
pot about eight years ago and have never repotted it. It thrives.

I suspect you are somewhat meagre with the watering.

The right adjectives would be "lazy" and "irregular", not "meagre".
{:-))

Then it will be OK.
Most Japanese acers grow on mountainsides and expect to be dry at
the
roots from time to time.

Where I live at the moment I am having to tip water out of trays
under
pots containing small trees.
I am supposed to be watering them for a
neighbour but we had 100mm of rain in the last two days!

What on earth are these trays doing under the pots? Why don't you
suggest to the neighbour that they are probably doing more harm than
good? Pots are supposed to drain off excess water freely. Mine stand
on open paving, on detachable feet, to raise them above the surface.

Franz