Monday, July 9, 2007

ISA HK/China --- specification for trees produced to International Standards

***Station Mail is for the information of Station Members only. Comments form non-Station Members will not be entertained.***
Dear Station members,

Eurasian Tree Farm (ETF) has been invited to produce a Nursery Stocks Specification for Landscaping Trees for private & Govt sectors in HK. The Station Manager reckons that if input is to be given to specific clients only, it may as well be publicised in Station Mail for anyone interested. Information sharing is one of the virtues of this Station & therefore why this one can not be shared?

So, please find attached the first version of the Nursery Trees Specification at ETF for anybody's interesting information.

This specification may be the most comprehensive Nursery Trees Specification that HK has seen so far for landscaping, & it was written with the production & landscaping experience of the Station Manager in his 23 years in the industry. Even though it looks complicated in many of its wordings to the commoners, it is really a dwarf when compared to the 129 page ANSI z60.1-2004 which ISA arborists around the world is using. Anyhow, this is a start & we'll carry on improving.

Dozens of Station Members have already visited ETF in the past two months & most are now convinced that the ISA tree recommendations can indeed be applied for nursery production even for China. It is also interesting to note that although ETF is surrounded by thousands of China tree farms, no even one of them has ever bothered to visit ETF to study the standard & production method for quality trees. Perhaps these Chinese tree farmers think that they already know it all.

On the other hand, the secret of success of ETF really lies in the knowledge & attitude in Structural Pruning. Even if the Chinese tree farmers would copy ETF in nursery design & logistics, they would still need to learn the hardest part which is the Structural Pruning in order to produce ISA trees. We have a Chinese saying that 江山易改,品性難移。 Wearing western clothes & driving western cars do not mean a person can speak western language too. What Chinese tree farmers lack really is proper knowledge & attitude in quality tree production, & this may take generations to correct.

Please note that this specification is really meant to apply to Excurrent Trees to be used for landscape, i.e. roadside trees & feature trees. Decurrent Trees can also be structurally pruned to achieve Excurrent growth form in nursery. After installation, continuous Structural Pruning would be required to maintain the Excurrent form which can be labour intensive. If not maintained, the genetic Decurrent nature of the tree will return & a Decurrent tree will be obtained at the end. Please also note that this specification does not apply to Topiary & other artificially shaped trees.

As this is the first attempt to write up something so complicated in our landscape history in HK & mistakes are likely to be contained. The Station Manager welcomes any constructive comment from our Station Members to upgrade this specification for the benefit of all in the Greenery development for our loving home of HK.

best regards,

Sammy Au
Station Manager


Specification of Nursery Trees (Balled & Burlaped, & Container Grown) produced to International Standard at Eurasian Tree Farm (ETF) in Guangzhou, China

(A) Tree Parts above Ground

1. A prominent Central Leader from base to tip, with any co-dominant branching starting at not less than 2/3 of total height measured from base, for Excurrent Tree or Decurrent Tree so pruned to Excurrent Form.

2. No Included Bark at any point of branch attachment in trunk & branches for good structure.

3. No Topping at Central leader or at lateral branches.

4. A Live Crown Ratio, which is the height of the living crown with foliage divided by the total height of the tree, is to be over 50%, with 67% at its best. This is for assuring the vigour of the tree with adequate foliage to produce food & for an even wind loading on tree. Please note there are species sensitive to lifting if no Root Pruning is allowed at time of delivery, which may lead to the dropping of some leaves. In such case, the lower branches in the crown should still be living & be able to re-generate leaves after installation. The shape of the crown should simulate that of a ‘tear drop’ for maximum wind resistance.

5. The diameter of the lateral branch is less than 50% of the diameter of the trunk at the branch union for the development of a Strong Branch Attachment.

6. The lateral branches should not overlap one another when viewing vertically from top. The ideal arrangement is that of a Spiral Staircase for good air & light penetration.

7. A noticeable trunk & branch Taper from base to tip for maximum wind resistance.

8. No pruning wound or mechanical damage of any kind which includes canker & cavity on trunk or branches of size exceeding 10% of the trunk diameter, or 50mm in length or diameter, whichever less is to be preferred.

9. A Balanced Crown with full foliage for even weight distribution & wind loading. No lop-sided canopy is allowed.

10. No major pest problem on any part of the tree. Pest attack or chlorosis at 5% of total foliage is acceptable, because foliage is a temporary organ which comes & goes. Cold damage or wind damage to foliage is acceptable if delivery is to be made right after such climatic condition. Tree without foliage is acceptable if deciduous in nature & delivered during cold season.

11. Minimum Canopy Width of tree at widest is to comply with the followings:

Trunk diameter (mm) Minimum Canopy Width (m)

25 1
50 1.5
75 2
100 & above 3

Please note the width of the cargo compartment of an average lorry on HK road is around 2.5m. Anything wider than 2.5m may have to be cut back to fit (i.e. Topping) & this is not encouraged at time of delivery. Crown Reduction should be done at the production stage, not delivery.

(B) Tree Parts below Ground

1. Diameter of Rootball is to be at 10 times or more than the diameter of the trunk for maximum transplant survival, e.g. a 20mm trunk tree should have a rootball of minimum 200mm diameter.

2. No Girdling Root / Circling Root system. All roots are radially emitted from centre of root crown.

3. No Defective Roots such as ‘J’ roots in any part of the root system.

4. No root of above 20% of trunk diameter growing out of the rootball. This is to ensure minimum ‘transplant shock’ if such defective root exists & be severed during lifting.

5. Roots are healthy & living, showing a white colour appearance in general. Dead roots are generally brown or black in colour.
6. Rootball must be filled with roots & be compact. Foreign soil filling to enlarge rootball is not to be allowed. This can be determined by ‘Push Test’.

(C) Others

1. Tree should be able to stand up on its own without staking. Tree that can not stand up on its own indicates inadequate sized rootball or poor root development. ‘Soft’ trunk requiring staking to stand upright is not allowed. ‘Soft’ trunk development is generally due to a lack of taper or inadequate cellulose formation in the trunk tissues.

2. No fertilization has happened before delivery to avoid root burning.

3. Please note that the above specification can be Species Dependent which by nature & genetic, may not be able to achieve the above growth form even by Structural Pruning, e.g. Toona & Macaranga in terms of Live Crown Ratio. Please contact ETF for further details on the desired specification for such species.

4. Please note the above specification does not apply to Palms.

For any queries, please contact Eurasian Garden (Hong Kong) Ltd in Hong Kong at for further information.


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