Saturday, August 22, 2009

ISA HK/China --- Local 'Instant Effect' of Aug 2009

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Dear Station Members,

Attached are 3 counts of Tree Planting enquiries sent in by Station Members in the month of Aug 2009. We shall discuss the technical aspect of them as an education scenario only.


1. Scan008

This event has been exposed by local newspaper already & much of HK has acknowledged the fact that this tree planting could not be regarded as something sustainable, but would rather be taken as a quick 'Instant Effect' to satisfy greenery requirement.

The species chosen is Cinnamomum burmanii, which would grow to +8 m tall with a crown spread of +8 m easily, if room can be allowed for upper ground & underground development. One of the trees so shown was already blown over by wind possibly due to lack of root anchorage, & staking did not appear possible for a growing pot of such narrow width to be effective. Also, the pot is unusually tall with a small diameter bottom to balance the tree in wind, & was probably used while expecting root growth to be downwards instead of sideway.

If the trees in these pots are allowed to mature in time, the Wind Sail Effect in the canopy is likely to topple them owing to the top heavy situation. For all the work & cost so spent in this tree planting, the Arborist could simply see no long term benefit but rather potent liabilities if it is allowed to stay.

2. Rooftop Planting in North NT

Form the photos so given & attached, this appears to be a case of Roof Top Planting in the name of 'Greening' taken to the extreme for another 'Instant Effect'. Quite possibly the developer did not realize that they are in effect putting a full range of Time Bombs on their houses for future headaches.

To start with, anyone wanting to put trees of such maturity on a roof top, has possibly ignored the fact that trees will grow. Even if the planter size is big enough to let this tree grow to a certain extent, then what about the Wing Loading thumping tons of wood up & down in future on a roof top to likely damage building structure & waterproofing? This may not happen instantly, but what about in a few year's time?

Also, the species chosen appeared to be Ficus benjamina which can grow to +20m tall & +20m wide. Even if the structure can support the future weight, then what about the huge canopy in future catching wind in case of a typhoon? Wind is passing at higher speed away from ground, & the higher it is, the stronger it becomes. Wind is the biggest enemy of tree & can we sacrifice safety for 'good looking' or 'cooling' for tree planting?

Does the whole thing make sense?

3. KLN Tong Tree Planting

It was said that the developer wanted to green the wall behind & therefore a row of fast growing trees (Ficus benjamina again) were installed for an 'Instant Effect' to add Greenery. The trees were planted approx. 1.5 m apart with canopies already touching each other, & the planter width did not exceed 0.6 m. Any sensible person can imagine what is going to happen there in 3 years time.

While the canopy of the Row Trees is going to spread into the driveway next to it, it may be pruned back constantly for traffic passage. Crown Raising to be combined with Topping are likely to be performed by those 'Specialist Contractors' if no Arborist supervision is required. Also, since the canopy overhanging the wall on the opposite side would require Tree Climbing to prune, this side may be left unpruned since it does not obstruct traffic. Then we may get a row of lob-sided trees to favour away from the Driveway. In wind, the whole row of trees may simply collapse, or damage the wall structure with roots pushing in all directions.


Since the above information was received as recent as only this month, it simply shows how heavy the workload it will be for the future Tree Management Office (TMO) to correct Tree Malpractice all over HK. It is always true that while we try to prevent trees from becoming dangerous, we should not allow more trees to be planted to become Time Bombs in the name of 'Instant Effect' or 'good looking'. The future TMO has a duty to lead HK to plant safe trees, & monitoring Tree Planting Design is one way to ensure Quality Tree Planting. Any design not following international practice or scientific requirements, no matter in what name it says, should not be approved by the TMO for installation, or else we may repeat mistakes of the past. It is always mother Nature makes the Rules, not anybody for tree planting.

ISA HK/China has great faith in the future TMO to correct Tree Malpractice in HK, & for this we shall support the TMO to the last word always.

best regards,

Sammy Au
Station Manager

"If a tree is not designed, installed, maintained & inspected properly, it is likely to become a liability rather than an asset."

"Trees are good for the community. Trees need care like human beings. Arborists are the Tree Care Professionals."

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