Monday, July 9, 2007

ISA HK/China --- Review of BS 4043 Tree Transplanting

Dear All,

The BS 4043:1989 ' Recommendations for Transplanting Root-balled Trees' is still very much in use in landscape specification in HK today. This Station has taken some time to make an attempt to review in general this valuable BS against ISA practices of the following publications, in major with other ISA research:

1. Arborist's Certification Study Guide, by ISA
2. Arboriculture --- Integrated management of Landscape Trees, Shrubs & Vines, by Harris, Clark & Matheny
3. Priciples & Practice of Planting Trees & Shrubs, by Watson & Himelick

The above 3 books can be purchased from ISA website of .

In general, the recommended practices mentioned in this excellent BS are actually quite similar to ISA practices, like ' prepared rootball should be 10 times the trunk diameter ', prior root pruning, transplanting at dormant season, & ' trees should be handled & lifted by the rootball only ', & ' small nursery stocks are likely to be the most adaptable to change', etc. ' The top of the rootball should not be below the surrounding soil ' & ' topsoil should be re-used & as much of the indigenous soil as possible should be retained to avoid a distinct interface between the planting pit & the surrounding soil ' are also very much in line with ISA recommendations. In viewing our planting sites in HK, it seemed that this BS has not been followed strictly enough & has led to many undesirable transplanting operations in the past among developments.

It may be interesting to note that this BS was written with the intention of working with temperate trees in the British Isles in 1989. No specific reference was made for sub-tropical & tropical trees, although some applications would be similar for both regions.

This Station has noted the following points as compared with ISA practices in this BS as follows:

1. No information is given on Girdling/Circling Roots for container grown trees. When production period is excessively long using containers, Girdling/Circling roots will develop when the elongated roots hit the sides of the container. Girdling Roots will kill the tree in the long run by constriction in the root crown region. It is like gradual strangling. This practice happens frequently in China nurseries where they think intact rootball can quell transplant shock with container production. Then the tree aould topple later by the production of Girdling Roots.

2. In sec. 2.5 of the BS stating that ' pruning can reduce the risk of excessive transpirational loss', for ISA practices would recommend a larger rootball to be dug instead, since foliage is needed to produce food for the upper & lower ground parts of the tree & removal is not preferred.

3. In sec. 3.2.4 of the BS for mulching, UV stablized polythene sheeting is allowed to be used as mulch. This may lead to irrigation difficulties or ponding on top of this plastic sheet during rain. This will not be an ISA practice.

4. In sec 3.3.1 of the BS stating ' the sheet mulches may have to be removed to allow soil to be added to restore the level ', there would be a different approach with ISA where soil addition to planted trees would not be generally recommended as an after care. New soil addition may suffocate the roots.

5. In Fig. 4 of the BS showing the wooden stake driving through the rootball of the planted tree, this would definitely not be an ISA practice. This may damage structural roots on the way.

6. In Fig. 5 of the BS showing the calculation of the staking height, this again would not be a standard practice for ISA since ISA arborists would prefer to stake only as low in a trunk as possible in order to build trunk taper.

7. In Fig 6 of the BS showing stakes driven at an angle of approx. 60 degree to the horizontal, whereas ISA practice would require the stakes to be driven at the same angle of the ties to allow maximum friction of stakes in the soil during pull.

All in all, the BS 4043 together with the BS 3998 would provide some very good guidance to tree transplanting in HK. If these two BS have been strictly followed, no topping & miniaturized rootballs would happen in many of the transplanting jobs. Trees would not be planted too deep & mature trees would not be recommended for tree transplantation. A number of other ill-treatments would also not occur. Our problem seemed to be not lying with the BS themselves.

It seemed to be that the BS's this Station has reviewed so far have advocated similar tree practices to ISA, although ISA would relentlessly update their practices, practically after any major conference or seminar, through continuous research & reporting, more often than most other national standards of the world.

best regards,

Sammy Au
Station Manager

1 comment:

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