AND PRINCIPLES OF ROOT RESTRICTION - BY FRED FIELD
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In Japan the history goes back 800 years, in China possibly
1000 years and the question arises why did they do it?
With the Japanese it mirrored natures adversity in small trees
which could over come some extreme conditions which older
trees couldn't. To Bonsai successfully one needs to start with
very small trees (Large trees struggle with shock). My own
research has shown and confirmed the many and varied ways of
1. Binding the roots in a container.
2. Growing on a cliff face.
3. Minimising the available water.
4. Growing in a hostile environment.
5. Use of paclobutrazol hormone restriction called Cultar.
We all assume all trees have roots for the same reasons which
couldn't be further from the truth , as most of them in the
sea for instance, are used for anchoring and on the land it is
again for anchoring and for uplift of water and trace
elements, but most importantly above all these needs is the
fact roots are the brain box of the plant as it determines the
whole programme of how it develops, it has to overcome
environmental change that humans couldn't survive 1 day in.
Over millions of years plants have hybridized and genetically
changed to survive
and flourish, humans don't, we scavenge on what plants
produce, directly and indirectly. It is this long line of
thinking and awareness to plants about what is actually
happening such as the stages of suddenly knowing that insects
are out there and devising a plan to use them but to reward
them a plan of partnership as old as algae and lichen what has
this got to do with roots? - Quite a lot - the roots haven't
changed much but the genetically the plant or tree above the
The root system surveys the situation, thus in the ground as
to what it can utilise such as weather, mineral and area and
this is assuming we have brought the tree from a nursery. This
will take some time for the tree to work out as it was
probably grown in a nursery 200km away, where water comes on
each day at 5 pm so a new plan must evolve, this is
conclusively proved as to why it takes so long to start
growing after planting. If we take a cutting or seed off a
tree growing right beside our proposed extension the seed
already knows a lot about the conditions that pervade there,
so genetics play a vital role in the wellbeing of the plant.
Genetically plants can change much quicker the other life such
as insects, animals and they are also bigger opportunists than
the recipients. So we have established that roots communicate
with the top of the tree through the production of auxin at
the tips of branches. One could assume that the leaves have
some say in the day to day running of the plant only
mechanically by shutting off the stomata to stop
transpiration. The leaf is a factory designed to
photosynthesis of which contribute to the development of the
fruit and growth. The Roots will still generally work out the
long term programme.
By restricting the roots will immediately to the following.
1. They will immediately assess the situation as to how much
room is available and to give an example - pine trees in a
forest all generally grow to the same height at the same time
in the shady side of a hill as the sunny side - the roots from
each tree survey an area to the next pine tree, so one would
assume they are complimentary rather than competitive, and
they don't produce many seed cones. ( No attrition!) Compared
to a lone pine in the middle of a paddock in say inland
Canterbury, continual production of seed cones, this could be
attributed to the roots assuming that it was alone and must
reproduce to protect the species or the constant threat of
attrition with wind and draught sends the same message. A
combination of factors in more likely.
2. The roots instruction will be to reduce the size of the
leaf to restrict transpiration.
3. Woodstock production is reduced. Excessive fast Woodstock
production invites more disease and insect infestation as the
cell structure is weak, also fruit will abort as the
carbohydrates are diverted to Woodstock productions.
Leaves are protein driven and need nitrogen and fruit is sugar
driven and undergoes a different set of biological process and
one assumes that if the carbohydrates etc are not used for
wood production they will be stored in the cambium for
conversion to sugars.
4. Growing in root restriction bags Above The Ground offers
many advantages to the commercial growing, aeration of roots,
mobility of one crop in Tunnel Houses to another.
5. Growing in Ground Bags is successful if the plant is
started small so it can plan its future for survival. These
are deep cylinder bags, where the plant can always find some
moisture down deep. (These must be in free draining soils).
6. The success of the tree in BAGS is to physics, not biology
and the relationship between diameter and pressure. Roots in
the bags do not encircle the bag above the ground, they air
prune, in the ground when moisture disappears they wall off
and shut down, and when conditions improve, the process of
producing fibrous roots starts again. A tree can literally
survive on 1 litre per week in the ground bag. Over watering
is the demise of 80% of fruit trees, over fertilisation say
15% and under watering 5%.
7. ROOT RESTRICTION BAGS also offer a new approach for
landscape design, allowing virtually any species of plant to
be used in conjunction with each other, with better
utilization and contrast in garden design for small spaces.
Plants used in orchards and landscape designs have the added
advantage that they have capital value separate from the
location in which they were planted. They can be traded at any
stage of their growth or age and relocated. They could be just
as mobile as their owners, their pet animals or furniture.
The research we have been doing over the last 20 years re tree
growth control is many and varied and is based on observations
and trials on many types of trees and shrubs, so the need to
research the tree of its origins to modify the type of root
restriction to achieve the optimum result is of considerable
importance. We have now combined a form of cincturing of the
tree to apply pressures at certain points to assist root
control, once the tree has attained maximum growth, sometimes
a combination of certain over invigorated trees succeeds.
Advantage of bag control.
1. Minimum of pruning.
2. Capital investment - tangible asset.
3. Allows for manipulation of the season such as moving trees
onto glasshouses for early production of holding in chillers
for late production.
4. Higher yields per hectare.
5. Claim for depreciation of trees when appreciating.
1. Slightly higher set up costs.
2. More preparatory work - this is all offset with long term
management of large trees.
Root control is here to stay for basic reasons such as:
1. Grower controls the orchard not the orchard controlling the
2. Higher sustainable returns per hectare, with the option of
leasing land and putting capital into production.
3. Low cost of protective structures against birds, wind, and
frost to shore up unnecessary risk.
Fred Field/ Field Horticulture