Lynn,
Unrestrained top growth should do the trick for all trees that I have worked
with. Can't think of one that did not work that way.
Jerry Meislik

Hmmmm. That's a tough one. Obviously, the more foliage, the more
transpiration, and the easier to overwhelm a weak root system.
However, if you put the tree in a high-humidity tent, which would
minimize transpiration, would greater foliage improve root growth?
There would be more energy available for growth, but as I explained a
couple weeks ago, sugar is moved in plants using a "source-sink"
mechanism, so sugar won't move to where a potential root *ought* to
be, only to a new, actively growing root. Besides, some research
shows that high sugar concentration inhibits lateral root development.

And how do you get root initiation? By the action of hormones.
Auxin, produced by apical meristems of shoots stimulates lateral root
growth. So if you prune the top growth, you will temporarily be
reducing auxin, although as soon as back-budding occurs, and all the
new branches begin to grow, the amount of auxin will be increased.

So a tree that buds back quickly and easily would probably produce
new roots rapidly, too. However, if a tree was in real trouble, it
might be better to leave the strong apical meristems in place. I
don't know; I'm afraid I'd be stuck with trial and error.
--
Nina Shishkoff

Frederick, MD

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Thanks to you all, Alan for giving me cause to actually think
and Jerry, Jim and Dale and Nina for helping the gears
work.
I will have to figure my chances but I have some good
thinking experience behind my judgments now. Previously I
didn't much hesitate.
Lynn
----------------------------------

From Dr. Nina:


Lynn,
Unrestrained top growth should do the trick for all trees
that I have worked
with. Can't think of one that did not work that way.
Jerry Meislik

Hmmmm. That's a tough one. Obviously, the more foliage,
the more
transpiration, and the easier to overwhelm a weak root
system.
However, if you put the tree in a high-humidity tent, which
would
minimize transpiration, would greater foliage improve root
growth?
There would be more energy available for growth, but as I
explained a
couple weeks ago, sugar is moved in plants using a
"source-sink"
mechanism, so sugar won't move to where a potential root
*ought* to
be, only to a new, actively growing root. Besides, some
research
shows that high sugar concentration inhibits lateral root
development.

And how do you get root initiation? By the action of
hormones.
Auxin, produced by apical meristems of shoots stimulates
lateral root
growth. So if you prune the top growth, you will
temporarily be
reducing auxin, although as soon as back-budding occurs, and
all the
new branches begin to grow, the amount of auxin will be
increased.

So a tree that buds back quickly and easily would probably
produce
new roots rapidly, too. However, if a tree was in real
trouble, it
might be better to leave the strong apical meristems in
place. I
don't know; I'm afraid I'd be stuck with trial and error.
--
Nina Shishkoff

Frederick, MD


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******************
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At 08:32 AM 6/16/03 -0400, Nina Shishkoff wrote:
Lynn,
Unrestrained top growth should do the trick for all trees that I have worked
with. Can't think of one that did not work that way.
Jerry Meislik

Hmmmm. That's a tough one. Obviously, the more foliage, the more
transpiration, and the easier to overwhelm a weak root system.
However, if you put the tree in a high-humidity tent, which would
minimize transpiration, would greater foliage improve root growth?
There would be more energy available for growth, but as I explained a
couple weeks ago, sugar is moved in plants using a "source-sink"
mechanism, so sugar won't move to where a potential root *ought* to
be, only to a new, actively growing root. Besides, some research
shows that high sugar concentration inhibits lateral root development.

And how do you get root initiation? By the action of hormones.
Auxin, produced by apical meristems of shoots stimulates lateral root
growth. So if you prune the top growth, you will temporarily be
reducing auxin, although as soon as back-budding occurs, and all the
new branches begin to grow, the amount of auxin will be increased.

So a tree that buds back quickly and easily would probably produce
new roots rapidly, too. However, if a tree was in real trouble, it
might be better to leave the strong apical meristems in place. I
don't know; I'm afraid I'd be stuck with trial and error.

Nina, et al

I have spent years closely studying the response of plants to pruning. Your
instincts are correct, leave meristem growth to quickly rebuild a new root
system. I have written several articles about this effect at my website,
one of them is Pruning Bareroot Seedlings.

I have even done comparison studies on establishing Acer palmatum var
atropurpureum plugs into my 2 3/4 inch pots. I divided 100 plants, half
were top pruned (this was early summer) and the other half were not pruned
at all upon shifting them from plugs to pots. They were placed side by side
in the shade. By the end of summer, the unpruned ones were completely root
established and pushing new growth, the top pruned ones were just sulking.
By the way, at that time I thought the opposite would happen! That was
probably eight or ten years ago. Since then, I have paid very close
attention to balancing growth and transpiration so that I could maintain
maximum terminal growth.

That is the key, maintaining water balance. In winter, it's easy,
especially for deciduous plants. You can start enormous plants with
practically no root system. We do it all the time with bareroot fruit and
ornamental landscape trees. Bonsai and other container plants are no
exception. The very long period of low or no transpiration coupled with
cool moist conditions allows you to leave maximum meristem growth. Pruning
only delays the response and pushes you farther into hot weather. I have
got this process down to where I lose very few plants now. I get two or
three year old bareroot seedlings and cut off 2/3 or more of the roots in
order to get them in my 2 3/4 inch pots. the tops are sometimes two feet
tall. By about this time, they are beginning to push new growth and have
nearly filled the pots with roots.

Summer is more difficult because the transpiration is very high and it must
be limited in some fashion. I find that removing foliage is superior to
actual pruning, which removes the meristem and delays the growth response.
Bud break following leaf removal is quite fast and results in a large area
of leaf surface restored in a very short time. Knowing how much foliage to
remove and how much protection to give a plant in summer just takes
experience, there is no way around it. I am still actively repotting small
and one gallon plants that are in collapsed soil mix with very poor root
systems. Fortunately, the weak roots have already limited the amount of
foliage so little to no pruning is required when they are placed under
shade cloth and given some extra watering when it is very hot.

One area that is still testing my powers is conifers. These guys just don't
like summer repotting. I have just about learned their limits but I still
get caught. This year I am losing about a half dozen nice white pines
because I repotted too late and didn't give them enough protection. I knew
I was pushing the envelope, but I was afraid they would not survive anyhow
without repotting. I still think I could have saved them if I had the
proper facilities, but the new nursery isn't that far along yet. What they
need is grafting house conditions, where both temperature and humidity can
be controlled summer and winter, usually cooler than regular greenhouse
conditions.

If you want to generate new roots, general heading back of plants is not
the way to limit transpiration. Prune methodically, remove unwanted
branches, and that isn't enough remove foliage, but maintain those terminal
buds. You can correct any aesthetic problems later, after the plant is
established.

Brent in Northern California
Evergreen Gardenworks USDA Zone 8 Sunset Zone 14

http://www.EvergreenGardenworks.com

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Folks

I sent this message to Theo, who asked for a private reply, but since it
bounced at his address, I am just going to post it here.

Brent



Theo

Sorry, this is so late, things are a little busy around here. See comments
below:

At 09:22 AM 6/19/03 +0200, you wrote:
HI


My maple has been repotted in beginning of April and probably I cut
too much roots and washed too much the root ball and made a new mix
that is very drying with leaf mould sand and akadama

Yes, I try to limit or completely avoid root pruning when repotting during
the growing season. Washing out all the old soil isn't a bad practice IF,
it comes out easily, the roots are not disturbed, and you don't do it too
vigorously. I 'irrigate' tighter rootballs. I just keep watering and
watering until the water stops coming out muddy and starts to get clear.
The remaining soil particles are large enough to stay and much new porosity
is added to the remaining root ball, so you get your drainage back. I then
just backfill the voids with new soil. I am still doing this even at this
late date, but the aftercare is important. They must not be heat stressed
afterward, shade, a lot water, humidity, and cool conditions should be
provided.

Since than has pushed out the first pair of leaves as usual
and since over 2 months no growth all is static the leaves are ok but
no elongation on twigs no new eyes opening back in the trunk or
branches .. just very few that do not burst out .. all is just
static!

That's because it is trying to regenerate the roots. What happens is that
the compromised root system does not have the leaf stimulus (hormone) to
promote new shoot forming hormones, so the leaves that open from stored
tissue carbohydrates open but don't grow. They will keep feeding the roots
until the roots are strong enough to begin growing again. When this
happens, then the roots will once again begin sending the shoot hormones
and top growth will start. When you prune both top and roots at the same
time, you really create havoc with this system. That's why I always
advocate doing one or the other but not both root and top pruning at the
same time.

It is a 20 years old 80 cmt straight Deshojojo jap maple
I fertilized regularly with mild fertilizer almost every other
day but nothing happens I do not dare cutting leaves as has been
repotted this year
shoulk'd I defoliate just a part of them to provoke growth ?

Older trees will have even more trouble getting the system working again
because they lack the vigor of more juvenile growth. Do NOT prune under any
circumstances or you will just create a bigger problem. The roots need that
leaf stimulus.

I am perplexed !
thanks for your feed back
Theo

All you can do is wait. New growth may come very late in the season, which
means that it will be quite soft going into winter. So the next drama will
be protecting it from fall freezing weather. You want it to grow as long as
possible to gather strength, but doing so sets it up for damaging freezes.
You should provide a place (outdoors, not in the house) where it will stay
between about 28F and 40F (-2 to +5C) for the winter. It is important that
it be cold so it will go dormant, but not too cold to avoid root damage.




Brent in Northern California
Evergreen Gardenworks USDA Zone 8 Sunset Zone 14

http://www.EvergreenGardenworks.com

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