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Re: tree roots

  • Subject: Re: tree roots
  • From: Len Phillips <lenphillips@yahoo.com>
  • Date: Sat, 25 May 2002 05:47:50 -0700 (PDT)

Hank,  Chopping off tree roots with a shovel, to plant hostas can actually
be worse than you imagined.  Many years ago I planted a beautiful garden
under a specimen Japanese Maple.  Many roots were cut and the following
spring, 2/3's of the tree was dead.  The tree was saved, but it never
looked the same again.

Chopping at the roots is the same as tearing a branch off the tree, it
provides access for diseases and insects.  If you must cut a tree root,
make sure you cut it with your pruners or loppers.  Make it a smooth cut
and preferable at a joint with other roots, just like pruning a tree. 
Cutting it anywhere encourages sucker development, so instead of one root
you will get 20 roots, none of which will be healthy.  Also do not cut any
root larger than 2 inches in diameter, without consulting an arborist. 
Unless of course you don't care if the tree dies or falls down during a
wind storm.  And if the tree falls onto your neighbor's property, you are

Tree roots grow at the very tip, just like the bud of the plant.  Moisture
and nutrients are sucked in at the very tip and they are transported along
the cambium layer, just like the branches.  As the tip grows forward, it
uses the bulk of the tree to push against.  Tree roots will also go out as
far as the tree is high, to provide the necessary support, not just to the
drip line as commonly believed.  A tap root occurs only on seedlings and a
very few species, unless you have ideal growing conditions deep under the

Tree roots are also very opportunistic and will go where air, moisture,
and nutrients can be found.  If you are watering and fertilizing your
hostas, yep, that's where the tree roots will go.  Both roots are after
the same air, moisture, and nutrients in the same 18" of topsoil.  

I have found the best results are achieved by planting all of my hostas in
competition with tree roots, in large black nursery pots.  That way the
soil can be ideal for the hosta, the hosta gets the water, and the tree
roots get the overflow out the bottom of the pot.  You do have to dig a
hole for the pot, but I avoid the major roots when setting the pot and
keep using the same hole over and over, despite what hosta may be growing
in the pot.  

I have also discovered that you have to dig the pot up once a year to cut
the fine tree roots away from the pot.  These are feeder roots that are
after the moisture that is available along the sides and bottom of the
pot.  If I didn't do this, the roots would eventually crush the pot.  How
much time does it take you ask?  I have 250 plants in pots, and in two
days, I can dig them all up, cut away the small feeder roots from the
tree, and put the pots back in the ground.  However, when I have the pot
out of the ground, I often check to see if the hosta has become pot bound.
 If it has, I repot it to a large size.  I will also take advantage of
this time to divide the 3 year old plants for spring sales.  Now my labor
effort is four days.

There are also many other advantages of the hostas in pots.  For example,
when breeding, I simply pull the pot of one plant and set it next to the
other parent and do the breeding side-by-side.  If I don't like the plant
combinations, it is easy to rearrange the design by moving the pots and
reusing the holes with better combinations.

Let me know if you have other questions.  My background is 30+ years in
landscape architecture and arboriculture, so there aren't too many tree
questions that I haven't answered.

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