ISA HK/China --- Big Spreading Trees in Hawaii

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Dear Station Members,

On the last day of the 2007 ISA International Conference, a walking tour was organized by the Hawaiian Society of Commercial Arborists to visit their city & park trees. What was most impressive for the Station Manager was to see the many Big Spreading Trees growing in city parks of Honolulu for public enjoyment. A few photos of them are attached for general information & comparison with the Shade Trees growing currently in our parks & open areas in HK/China.

It can be seen that the crown diameters of these Big Spreading Trees are normally over 40 m & the Live Crown Ratio (Height of Foliage / Total Height ) is generally over 60%. This shows that the trees are having adequate foliage to produce carbohydrate from Photosynthesis & will have good wind resistance due to their low Centre of Gravity. It can be also noticed that these trees have been structurally pruned all the way & incorrect pruning such as Topping or Lion-Tailed Pruning was not detected in the canopy. There were hardly any decay, cankers, galls & mechanical damage on the tree body, showing that the trees were maintained in good health. It was very apparent that these Mature Trees have been given good care all the way so that they can grow to such aesthetics, health & structure.

How often do we see Big Spreading Trees in our city parks & open areas as comparable to these in Hawaii, no matter in public or private properties?

Some would say HK has not got the space to accommodate Big Spreading Trees. This Station would argue that if we do have space to plant just one Big Spreading Tree, at least 10 smaller trees would be installed instead to occupy the same area. It seems that we tend to enjoy quantity, never mind the quality.

Imagine how inconvenient it is to manoeuvre under 10 tree trunks & branches rather than just one in the same space. Can we cycle or stroll under 10 trunks without bumping into one by accident? Then what about the competition for water & nutrients of 10 poor trees all squeezed together in a tiny forest. Would pests & diseases not spread faster for 10 trees? Would it not be another HK housing condition in the 1960's ??

Tree Selection in HK would generally go for 'flowering' as the priority because some reckon that colour & scent are the primary amenity of a tree. Some do not understand that what's seen flowering in books or computers may not flower at all on site, becasue flowering requires success in vegetative growth beforehand. Then how many of us would consider the amenity values of the ' flowering' tree after flowering. Also, do flowers stay on forever? Of course not, probable for something like a month at most for general species. Would anyone then query the wind resistance ability of the ' flowering' species so selected? The answer may be found in the many urban trees fallen after a small typhoon. Trees with a lot of flowers usually belong to weak wood & facts speak for themselves. For Arborist, it is always ' Mother Nature makes the rules, not us.'

The Station Manager has seen trees in Singapore mostly selected for health & structure to cool their city, with 'flowering' as a secondary consideration or just bonus. After all, flowers on trees are usually carried at the outer perimeter of canopy to attract birds & insects for reproduction, not for any purpose of we humans. They can hardly be touched or smelled unless you climb close. Then how many of us are Tree Climbers?

Trees in Singapore are recognized to be a great success & a valuable asset to their country. As a rule, trees are always selected by Arborists in Singapore in Govt landscapes.

Are Big Spreading Trees difficult to grow? The answer is no, but we need to master some basics. Arborists would have all the answers because they are the true Tree Care Professionals. To begin with, we need to select the right species with good nursery quality, & give them room above & below ground to grow. Structural Pruning is of paramount importance. Without corrective pruning, even the best nursery stocks in the world would grow wild in an urban environment. Then regular Tree Inspection & Risk Assessment are required to maintain health & structure, & to minimize hazards. Tree Climbing will be required for such work to penetrate inside the canopy. Platform lift can usually reach the outside of the canopy & may conflict with protruding branches.

Now we can see how the different knowledge of arboriculture are knitted together to produce Big Spreading Trees. Parts to be missed out in the operation will be like a broken chain. A complete treatment for a tree is like a complete diet for a person. There is simply no shortcut.

Big Spreading Trees are of such aesthetics & amenity values that we should develop them in HK/China. They are the genuine 'trees' described in our textbooks & they are loved by the public. Then are there any Big Spreading Trees anywhere in our urban area maintained in quality comparable to these ordinary Hawaiian park trees ? Station Mail would love to collect some photos to show the world indeed. This will make us proud.

A lot of the Big Spreading Trees so visited in Hawaii belonged to no more than ordinary Ficus, Samanea & Crataeva species. They are no magic to us in HK, but their proper tree care is magic.

In Hawaii, people were seen enjoying themselves under the relaxation of the Big Spreading Trees. Peace of mind can be felt while resting under the tree canopy, despite the ambient temperature of 32 C around. The benefits of trees can be truly appreciated when one is standing under or looking from a distance at these magnificent trees.

HK seems to be cooking political turmoil after 1997. Our public spent too much time in politics to grind heat for no positive results. If they would spend just a part of that time as an alternative on caring for our trees, maybe we can have a much more harmonious society for better living. In the rural past, villagers talked a lot about their trees. Trees were part of the community. We don't seem to hear this kind of conversation often these days. Is it because we keep losing our Mature Trees?

Maybe when our ' Victoria Park Uncles' in HK came to rest under these magnificent Big Spreading Trees, their conversation would change from political argument to measuring & comparing trees nearby. Would that not be the 'harmonic society' that our current Govt genuinely desire?

Big Spreading Trees are magic indeed. Do we want them, & how ??

best regards,

Sammy Au
Station Manager