Monday, October 22, 2007

ISA HK/China --- China Tree News (Expensive Flowering Trees & How to produce trees with Girdling Roots)

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Dear Station Members,

Attached are two recent Tree News from China:

1. Expensive ' Flowering' Mature Trees on high demand

As said before, China is an Old Dragon & the Old Dragon has its own standard of beauty.

It was said that the topped Lagerstroemia of approx 200 mm trunk diameter & 3.5 m tall grown in an 14 inch pot as shown in the attached picture, could fetch between 10,000 to 100,000 RMB in the China market. It was also reported that these topped trees were in high demand & customers flocked in to check stocks everyday.

What would be the hypothesis behind for the popularity of these apparently damaged trees grown in tiny pots among the China customers, which would be regarded as wastes in Western markets? The only probable explanation might be that they have a few flowers dangling in the canopy. Lagerstroemias are great survivors & can be grown from cuttings. Trees of these sizes after topping could survive, but were likely to develop cankers & cavities everywhere in the tree body. Growing them in tiny pots would also lead to the development of Girdling Roots.

Research has shown that while the canopy develops to an extensive mass above ground & the roots are girdling (circling) below ground, the tree could lose stability in the wind, or the vascular tissues at root collar could be strangled by the Girdling Roots to restrict flow of water & nutrients. When tree falls, it may pose hazard to people & property down below. Words will not prevent a tree from falling.

If these topped trees were planted in city parks or even in a backyard, they may never develop good structure & health. There is no way to stop the decay except by compartmentalization to take over. Yet compartmentalization in Mature Trees is usually very very slow.

So, these 'expensive' trees were sold for a lot of money in China. HK may be smarter than that, do we?

2. How to produce trees with Girdling Roots

Our brothers & sisters up north have apparently adopted this ' Double Containers' production system from pot plant production (maybe also Plug technology in Greenhouse) in the West. They would probably think that producing trees & disposable pot plants in horticulture would belong to the same category.

In the tree production so shown, Girdling roots are likely to develop in just a few months after containerization. When roots have reached the side of the container, they have nowhere to go but to circle around the container wall to become ' root bound ' to form Girdling Roots. Research has shown that once Girdling Roots have developed, they will have a tendency to stay that way even when severed in future. There seems to be no satisfactory method to completely eliminate Girdling Roots so far in tree production, once they have formed.

In pot plant production, shrubs or annuals are produced ' root bound' for maximum root absorption of water & nutrients, & to minimize transplant shock. Shrubs & annuals are smaller plants grown for scent & colour. Their falling hazard is low & their damaging strength is usually insignificant. Has anyone heard a person got killed or a car became crushed by a falling Azalea or Camellia?

However, when it comes to massive structure like trees & palms, the falling hazard is an entirely different story. Trees are something that would develop a big crown even with Girdling Roots. Top heavy trees with a restricted root system can be a great danger in wind. It would be like an office chair with spreading legs of just a few inches long. Would this chair remain standing if sat upon ? Then why should we use trees with Girdling Roots?

It is apparent that trees with Girdling Roots should not be used in landscape, because they can kill or damage when they grow big. Liability in using trees with Girdling Roots can easily be proved in Court since the exposed root system would give the evidence. The tree owner or relevant parties may be held liable for Negligence.

Horticulture & Arboriculture may belong to the same category for our brothers & sisters up north. Let's wish them good luck to their people, their properties & their trees.

Next time in a storm in China, would anyone like to stand under those trees with Girdling Roots, even if you have nowhere else to stand ....??

best regards,

Sammy Au
Station Manager

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