Saturday, October 27, 2007

ISA HK/China --- HK Tree News (Shing Mun River's 'Tree Murder'?'

*** Our weekly Station Mail is for the information of Station Members only, but Station Mail has given up copyright & can be freely circulated. For administrative reasons, comments from outsiders are usually not entertained & may be circulated within our system locally & overseas. Please note Station Mail is sometimes given in Blog at , although images are usually not attached due to size. ***

Dear Mr. X,

Thank you for your phone call & your direction for us to look into the attached newspaper cutting. We have noticed that you are not our Station Member but are able to gain access to our information for which you are welcomed. We are also accepting your challenge to openly reply your enquiry & to protect your identity which we actually do not know much anyway. On the other hand, we want to assure you that there is no such thing as 'change of wind' of our Station policies upon your knowledge of LCSD staff taking part in our recent Certified Arborist exam. Our values of Integrity, Professionalism & Participation with an attitude of fact-finding & truth-telling have remained constant.

In your request for us to comment on the event of your so-called ' Tree Murder ' at Shing Mun River, our Station is taking up the position of Tree Detective instead of Tree Doctor in the investigation. However, please kindly note that we are commenting with only the given facts & photos in the attachment & we do not have time to study the situation on site. Sending someone out on site for a detailed reporting will involve cost, & the current Professional Fess Guidelines of ISA HK/China would recommend a fee of HK$10,000.00 for an Independent Tree Assessment (ITA) report of this kind for about two trees in a day. Therefore, here you get a limited reply for free, but only with what this Station has seen in the attachment.

May we first advise you that the Station Manager has done ITA report of this kind on many occasions for various Govt Depts & public in the past. He is also currently acting as an Independent Tree Specialist (ITS) to the HKSAR Govt on several projects & he has produced Expert Witness reports at High Court for tree related disputes. He may be a fair & just person for this kind of reply to you.

In the newspaper cutting so shown, the Besser blocks would impede the flow of water & fertilizer application into the tree roots, but they would not stop them altogether. Water can leak through the gaps between the Besser blocks & reach the roots underneath, or the trees so shown would not be growing with such foliage density. One way to determine whether the roots are developing or not under the Besser blocks is to open them up for a visual inspection. You may wish to apply for permission to do this at the authorities if desperately interested. Facts will convince everybody better.

Trees generally do not require heavy fertilization like shrubs or smaller plants. The Arborist education would recommend an annual application of around 2kg/100 sqm for most trees in a general situation. For trees of inadequate health, we would recommend fixing the problem before fertilizer application, rather than the other way round. This may be contrary to what you may have learned from other sources in the past. Facts will tell you that trees growing in our AFCD country parks do not receive much regular fertilization from human application. Don't these trees perform?

What this Station would see as a challenge would really be that the trees so shown were planted too close to the boundary wall of other planting area which may lead to root cutting on the wall side. This may render wind instability when the trees have matured & there does not appear too much can be done to it. Remember, if a tree is not designed, planted & maintained properly, the tree may become more of a liability rather than an asset. In this theme, the design & quality stocks selection are of primary importance if we want to see an easy maintenance afterwards.

We wish our reply now can assist you to understand how a Professional Arborist would view an event as such. Arborists are practitioners & we tend to look at situation in a practical sense. Please do not mix us up with other disciplines with our due respect to others. However, we have our own professional direction to follow & we prefer to speak with facts.

You are always welcomed to provide feedback, although this Station may not publish it by open Station Mail each time. If you would like to go into this investigation further, this Station would advise you to employ a Certified Arborist to carry out an Independent Tree Assessment with the approval of the concerned authority, although the site work & reporting would cost you.

Thank you for your interest in our communication & we hope this reply will find you well.

best regards,

Sammy Au
Station Manager
ISA HK/China Station ManagerISA Chief Proctor for the HK/China RegionISA Certified Arborist / Certified Tree Climber no. ML-0174AT
Member of Tree Climbers International (TCI) in HK/China RegionInternational Tree Failure Database (ITFD) Coordinator for HK/China
Independent Tree Specialist (ITS) to the HKSAR Govt
Lecturer for Tree Supervision at CITA

Wednesday, October 24, 2007

ISA HK/China --- Introduction to Wood Decay Fungi (WDF)

*** Our weekly Station Mail is for the information of Station Members only, but Station Mail has given up copyright & can be freely circulated. For administrative reasons, comments from outsiders are usually not entertained & may be circulated within our system locally & overseas. Please note Station Mail is sometimes given in Blog at , although images are usually not attached due to size. ***

Dear Station Members,

An important part of Arborist's work in practising is Tree Inspection & Risk Assessment. This kind of specialist work would require all training of the Arborist & would demand all skills & knowledge of the practitioner. Not every Certified Arborist (CA) would like to take up the work of Tree Inspection & Risk Assessment due to personal competence & the legal liability involved. CA is held to a higher Duty of Care in Court & putting down the CA no. on an Arborist Report is a legal commitment. Identifying decay in tree is an important part in this kind of work.

Decay in tree is mostly caused by the micro-organisms called Fungi. There are hundreds of thousands kinds of fungi already discovered in the biological world & luckily only a handful would cause decay in living trees, whereas the others would decay dead trees (Saprophytes). In carrying out Tree Inspection in HK/China, Fungal Decay is a common occurrence in a lot of our mature trees.

This Station has taken some time to study & research into the vast topic of Fungal Decay in Trees already. Mycology is the name of the game & it is a huge & complex subject indeed. There are lots of textbooks & websites with good description in Mycology, but most would go beyond the need of an Arborist. Arborist would only need to know primarily the Wood Decay Fungi (WDF) for the work rather than antibiotic fungi, yeasts & parasitic fungi which are not of great relevance to our practice. Therefore in here, we focus on what we want & leave the rest to other experts.

Decay in living trees appeared to be mainly caused by two groups of fungi : the Basidiomycetes (BM) & Ascomycetes (AM). BM is the largest & most common of the WDF, & they are frequently known as Conks & Mushrooms. About 500 of the BM group are responsible for decaying living trees. The AM group is smaller in quantity & only a few significant species have been found to rot living tissues. Both BM & AM are capable to rot dead tissues (Saprophytes) which will lengthen their survival period in a natural environment. By doing so, they have become a threat to living trees & they would inflict wounds caused by natural processes such as sudden temperature change, or through artificial processes such as incorrect pruning.

There appears to be 3 common types of wood decay in living trees:

1. White Rot --- This is said to be the most common type of wood decay & the WDF responsible will first degrade the Lignin & then digest away the cellulose, leaving behind a white or bleached appearance in the decayed wood. White Rot is said to cause less wood strength loss then other rots in the initial stages of decay & Zone Lines would usually appear in the advanced stages of decay.

2. Brown Rot --- Brown Rot is said to be less common than White Rot & is usually found more frequently on conifers than hardwood. However, Brown Rot would decay away cellulose & would leave behind modified lignin, thus giving a brown appearance in the rotted wood. Brown Rot would bring about a significant strength loss even in the initial stage of attack & the wood would become brittle which may fracture easily under tension.

3. Soft Rot --- Soft Rot is primarily caused by AM fungi & the wood attacked would lose significant strength similar to Brown Rot. The Soft Rot & Brown Rot can sometimes be difficult to distinguish by visual means. Microscopic investigation may be necessary to carry out the taxonomy.

Decay in living trees is usually named after the position of occurrence, e.g. root rot, butt rot, sap rot, heart rot, trunk rot, etc. Healthy trees can carry out compartmentalization once the entry of WDF is detected. However, if the tree is in poor health or under stress, the WDF will advance with repeated attacks on the boundaries, sometimes with the help of other pathogens, to spread radially & longitudinally until the cambium is killed. Then the WDF will carry on their living cycles on the dead wood & seek opportunities to attack other living wood. Removal of dead wood alone does not seem to minimize infection, since the spores of the WDF are usually air-borne. Proper cultural practice appears to be more effective in controlling WDF in reality.

Among the hundreds of WDF active in our environment, the 3 most significant culprits in damaging living trees appear to be:

1. Armillaria spp --- Commonly known as Shoe-String root rot or Honey Mushroom. This group of WDF is actually edible, if you can clearly identify them (Warning: Most mushrooms are toxic especially the colourful ones. Do NOT just eat without proper identification.). Armillaria ranks among no. 1 as common in decaying root & lower part of a tree. It attacks & degrades the root system, weakening the infected tree to fall in wind. The fungal threads of Armillaria are said to be bio-luminescent. They tend to glow in darkness, giving them a name of ' foxfire' in wilderness.

2. Ganoderma lucidum --- This is the Wooden Ear that is sold in Chinese medicine shop. This WDF is easy to identify by its varnished mahogany appearance in its annual fruiting body. Nevertheless, this is the no. 2 in common to infect living trees. It occurs near the base of the tree & attack roots. It can kill cambium of roots & decline a tree to create potential failure. However, some experts reckoned the presence of the fruiting bodies alone would not usually be the only reason to suggest removal & other symptoms such as cracks, leaning, etc. would need to accompany the fungal attack. Different experts say different things all the time & the Arborist would need to rely on his/her own experience to judge the situation.

3. Ganoderma applanatum --- This WDF is also known as the Artist's Conk due to its saucer like fruiting body on base of trunk of living trees. It can also be found on dead trees & stumps as Saprophyte. This fungus is no. 3 in common as a WDF for urban trees & its presence would justify immediate removal as a sign of advanced decay. Ganoderma applanatum is a perennial fungus which can live up to 5 years or more, different from the above two WDF which are annual.

Basic understanding of WDF is essential for Tree Inspection, Risk Assessment & especially Tree Failure Analysis. WDF exist in our environment as part of ecology & we can not get rid of them unless we live in a desert. It may also be unwise to eradicate WDF or we shall have fewer agents to clean up our fallen organic matters. It may be really to promote the health & defense of a living tree to withstand WDF as wiser, rather than to constantly spray chemicals to rid them when detected. The emergence of WDF in a living tree is usually secondary to the primary cause of abiotic stresses which are likely to be caused by human intervention most of the time.

WDF should be studied together with Dr. Shigo's Tree Biology for a complete picture of Tree Pathology. Tree Pathology is necessary for Diagnosis & Treatment in writing up certain Arborist Report. Once again, it can be seen that building Arborist knowledge is like knitting a net. The different parts link together & missing knowledge would be like making a broken net ...

This Station works hard to develop Arborist knowledge for our Station Members in our territory all the time. This Station also appears to be the only entity in our territory providing such knowledge locally. Knowledge is what we need if we want to improve our Tree Care practice. This Station has to work hard.

More useful research will appear later when this Station has run over them one by one ...

best regards,

Sammy Au
Station Manager

The ISA Mission - Through research, technology, and education, promote the professional practice of arboriculture and foster a greater public awareness of the benefits of trees. (

Monday, October 22, 2007

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

*** Our weekly Station Mail is for the information of Station Members only, but Station Mail has given up copyright & can be freely circulated. For administrative reasons, comments from outsiders are usually not entertained & may be circulated within our system locally & overseas. Please note Station Mail is sometimes given in Blog at , although images are usually not attached due to size. ***

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