Thursday, November 4, 2010

Root Pruning Container Plants

How to Root Prune Container Trees & Plants

Spread tarp under planter to catch debris
Tree roots grow laterally-- 18" - 24" below the surface of the soil.  Unlike trees and plants that grow in-ground, container plant roots eventually hit the barrier of the container and die.**  

Brown  matted dead roots are incapable of taking up nutrition/oxygen or adequate water.  You can water and feed these plants constantly  but the plant will continue to deteriorate.   Transplanting to a larger container is an option.  Often, however, this is not possible and can be very costly.   An excellent option is pruning the plant's roots - this will completely
revitalize it.

The best time to do this is fall and late winter/early spring.  As long as the container/soil is not frozen.  (It is not recommended for summer -- for obvious reasons.)
Insert saw blade 2" from edge of planter

What you will need:
a fine tooth sharp saw
 -- blade at least 8-10" long
or Sawzall w/12" wood blade
sharp hand shovel (See link below)
potting soil
PHC BioPak Plus (see link below)
blue tarp
5 gallon bucket
tablespoon measure

The preliminary cut is  2" in from container edge; saw completely around the perimeter -- to  depth of the blade.  If you run into a large root --  go around it.  Using a sharp-edged hand shovel, remove the cut soil and roots.  Do not pull or yank the roots out from the root ball; if necessary cut whatever roots are still protruding.   After the first several inches are removed, continue to saw; remove material until you reach 18" depth (for a 24" planter; less for more shallow planters.  But don't worry if you can't get to 18" -  go as deeply as you can.)

This is how it will look after the pruning

Have ready the replacement mix: 1/2 potting soil with 1/2 compost/-- combine well.  Add the mixture --gently pressing in with fingertips to fill the planter.  Be gentle but firm.  You want to make sure there are no air pockets but after you add the water mixture you will be able to see where you will need to add more soil. 

Do not add more soil to the top of the root ball unless the "flare" of the tree is visible above the soil level -- then you can add a bit to the top. (see Rooftops Gardening:  Planting a tree -- the right way.)

In the bottom of your 5-gallon bucket add 6 tablespoons of the PHC Biopak powder.  Add water/mix thoroughly.  Water with this solution -- slowly -- allowing the solution to drain thru.  Add more soil mixture if needed -- water with solution again.  The soil should be completely drenched.  Mulch -- 1-2" depth.  Do not put mulch against the trunk of the tree.  Leave at least three inches around the perimeter.  Do not let the planter dry out.  Repeat solution treatment every two weeks until the soil freezes.  Repeat solution treatment in spring as soon as the planter thaws. 

Add soil and compost mixture

Water soluable solution specifically designed to reduce plant stress

**For this reason it is recommended that you plant trees and shrubs in planters that are at least 24" high -- but more importantly -- ones that are nice and wide to accomodate the lateral root development.  The depth of the planter is not nearly as important as the width. 

  • As you remove the dead materail along the perimeter -- if you come to a large root -- over 1/2" or more in diameter -- don't remove; go around it.   
  • Do not prune the crown/top of the tree at this point.  If you are doing the root pruning in fall -- wait until the tree is leafed out and then prune. 
Questons?  Contact me

See link below
A.M. Leonard for garden tools and
and Plant Health Care products
Alternative to PHC Biopak Plus 3-0-20 is:
   Bio-Plex Transplant Concentrate & Plant Enhancer
   or PHC Tree Saver
(Both are available from A.M. Leonard)
See also:  A.M. Leonard
"Trenching Shovel"  and "Soil Knife"

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