ISA HK/China --- 2008 Research on Tree Stabilization Systems

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Dear Station Members,

Attached is the latest research of ISA on the Tree Stabilization Systems for information to our local practices.

Tree Staking is a common practice in our landscape contracts due to the disability of landscaping trees to stand up in wind after installation. One major probable reason of this happening may be because the rootballs that come along with the nursery trees from China do not meet the international requirement of 10 x Trunk Diameter to have less weight below to stabilize the tree in wind. Another probable reason may be due to the low Live Crown Ration (LCR) which would raise the Turning Moment of a tree in wind since the majority of wind-catching area would be on top. Then if anyone would look carefully at most China nursery trees, they usually do not have good Taper to bend in wind as well.

The reduced rootball coupling with low LCR & poor Taper are again due to the common nursery production method in China. In most China nurseries, trees are planted densely like paddy or vegetables to maximize profit. Trees there have to fight for sunlight by developing a long slender stem which would lead to low LCR without Taper. Then when the tree is harvested, in order not to cut off the roots of the neighbouring trees as well as for manual carrying convenience while dragging it out of the densely man-made forest, the rootball has to be reduced & sometimes tree parts Topped. Occasionally there are trees planted in containers for hoping to minimize transplant shock, but either the containers would not meet the 10 x Trunk Diameter requirement or Girdling Roots would develop to make these trees a potential hazard in future planting.

Yet HK has to rely on China to supply nearly all our nursery trees today.

With trees of above qualities, we are not sure whether even the best Tree Stabilization Systems would help in protecting our landscaping trees in wind. Those with Girdling Roots would eventually become Time Bombs to hit somebody or something as well. The solution may really rest upon the use of quality trees that very few China nurseries can nowadays supply.

ETF has been promoting international nursery production methods to China growers but again has been ignored or even laughed at. Maybe if ISA Arboriculture would not develop among our brothers & sisters up north, HK will have to put up with using China quality trees, & then hope for the best ...

best regards,

Sammy Au
Station Manager

The ISA Mission - Through research, technology, and education, promote the professional practice of arboriculture and foster a greater public awareness of the benefits of trees. (http://www.isa-arbor.com/)