Thursday 15 December 2011

The Joy of Wood Anatomy

One of the most enjoyable chores is splitting wood. This article could just have well been called things you see while splitting wood.I know many people find this tedious and it can be dangerous. However if you know what you’re looking it can be a fascinating as any forensic drama on television.

Trees do not heal like animals, cells in wood, generally, do not recover when injured.

When compromised, the thick walled cells in wood are closed off from there adjoining cells by rot resistant chemicals like phenols and turpentines. Much the same way watertight doors are closed in a sinking submarine. These are the same chemicals that have been extracted for hundreds of years to produce wood preservatives and are the basis of many paints.

While these have largely been synthesized in modern labs, trees still produce these protective phytochemicals each time they are injured. It still surprises many people that trees are living dynamic beings, even if they are completely immobile in their environment.

Trees and woody shrubs contain or compartmentalize damaged plant tissue behind these strong chemical barriers and continue to grow over the injury. This process of compartmentalization prevents disease from entering the healthy tissue and overwhelming the plant and causing its death. A true case of life over limb, to save its life a tree will lose a damaged limb.

Back to the task at hand, while splitting wood you can find old pruning wounds and injuries that have grown over, encapsulated in new living wood. These barriers are not only resistant to pathogens they can be resistant to splitting as well! With modern hydraulic wood splitters you can power through these tough barriers and see the story contained within. I was splitting a piece of oak that had been removed for construction. The tree was at least sixty years old and very healthy when it was taken down. As I worked through the tree piece by piece I was amazed by the wood’s structure, beautiful rays and grains. As I split one large round I noticed an old branch stub that had been properly pruned many years ago and was now completely grown over. The areas of compartmentalization were clearly defined in all directions from the wound. Above, below and around, you could see the dark staining that prevented rot from entering the trunk of the tree. Whoever made the cut had done so properly and did not injure the branch bark ridge, a key anatomical structure in trees, speeding growth over the wound and preventing the expansion of decay. The most interesting part was that from the outside there was no hint, not a bump or blemish, of the drama, contained within. In fact if you look at the other side of the same piece of fire wood there is not a clue that the limb was removed and the tree had successfully grown over the injury. Any pruning no matter how minor or major is an injury to the tree. Successful limb removal involves knowledge of the art of pruning and the science of plant anatomy. I.S.A Certified Arborists are constantly updated on the latest pruning methods backed up by scientific research on tree wound response. Keep a keen eye on your firewood for these untold arbor-dramas and contact your I.S.A. Certified Arborist to plan and execute your next pruning project.

Tuesday 15 November 2011

A Tale of Two Leaders

The condition of co-dominance occurs when two leaders, or main upright branches, of a tree are of the same size. Some trees naturally have a strong central leader. Species like pin oak, sweet gum and white spruce are typical examples. These species can display co-dominance when pruning removes the dominant leader. When this occurs one or more new leaders will take on the role and start to compete. This leads to bark being included in the narrow “V” crotch between the two leaders. Over time this union becomes weaker and weaker as the tree grows apart.

Given the right conditions the two leaders will separate as the bark in the crotch splits and the tree tears itself apart. When the tree has been torn it is unable to form the protective boundaries that prevent decay from entering into the remaining leader. The weakened leader decays at an accelerated rate and can fail in an unpredictable manner.

Timely pruning of young trees prevents this condition from developing and causing major problems later in the trees life. If the condition already exists, cabling and bracing can help to prevent catastrophic failure and extend the life of mature trees. These measures are not complicated but need to be performed by a skilled technician. It can be quite interesting and even Gothic, the measures that people will employ to prevent their trees from splitting. The correct, effective solution of cabling and bracing are so subtle and non-obtrusive, that I have been called out on many occasions to point them out. Not so with the logging chains, mummy cables, steel welded bars, and other assorted paraphernalia I have seen used in less successful attempts.

Recently I was called out to look at a tree that I had on two occasion’s recommended remedial action to stabilize it. The tree, a mature Red Oak, had been covered with 6 inches of snow while in full leaf. The resulting stress pulled the 20 inch oak stems apart like pealing a banana. How unfortunate that the home owner declined to spend the small amount it would have taken to keep this 200 year old tree growing for another 100 years. Now they are faced with the cost of removing this giant tree a prospect many times more expensive than the original preventative action. A case of, “a stitch in time saving nine” if ever there was one. I.S.A. Certified Arborists are trained to identify and recommend corrective action to prevent the destructive forces that can be released in a co-dominant leader failure.

Saturday 15 October 2011

We Can Spare Some Green for the Forest!

Trees and green space provide real quantifiable benefits to urban environments. People can exist for years, life times some times in environments void of green space and nature. We call these environments prisons, jails and , penitentiaries. Part of the penal punishment process is the intentional removal of all these natural things that contribute to the human experience.
The results of this de-naturalization are predictable and well documented in both institutional and traditional housing situations.
Increased violence, isolation, decreased sense of well being and increased crime and suicide rates among youth.
The point being made is why would we allow residential rental housing to be built without mandating minimum provisions for setbacks, green space ,parks and recrea tional facilities.
Have our urban planers all gone for lunch at the same time? I suspect not!
Given the space, private home owners in all cultures develop their own gardens for their recreation and even landscape their front yards to create attractive vital neighborhoods.
In our home towns we need to advocate for the building of neighborhoods and the end of rental housing wear houses.
Green space is the catalyst for neighborhood and community development.
Central Park in New York City revolutionized the concept of protected, preserved, public space for all the inhabitants of the city to enjoy. It has been under development pres sure from before it's construction and continues to need vigilant protection.
Real-estate development is a business and rightfully is concerned with maximizing profits for share holders. Planning boards and urban planers act on direction from city co uncils who are elected by their constituents. People must be willing to step forward to make sure guidelines are in place to create urban neighborhoods and not allow tracts of housing wear-houses to be built. With no green space or recreation facilities mandated into development plans we will be left with socio-cidal landscapes with increased crime, higher youth, and domestic violen ce and ultimately the ghettoization of our cities.
These issues will add to policing and other public service cost increases. And as public service implies the costs of theses dysfunctional landscapes will be passed on to we the people.
Pennies lost on increased development costs will result in dollars saved in long term social costs.
And the result will be better, safer neighborhoods with increased property values.
Put in trees, sidewalks, play spaces and people want to stay, interact and form communities.
ISA Certified Arborists know the values of well placed green assets.
Many consult with developers and urban planners to help our cities to be as healthy and growing as the trees within them.

Thursday 15 September 2011

Major Cuts

Far from the latest denizen of destruction for the social safety net this article focuses on one of the most destructive practices in pruning. Removing large limbs or whole stems is destructive and can lead to major tree failures. This can be in the short term or even more dangerous, in the distant future.

The scenario usually involves a structure, like a home or garage that is being built or added on to, realizing the beauty and utility of a stately mature tree the home owner decides to locate the addition close to an existing tree. The dialog usually goes like this

” I would like to build X right next to this tree and the builder says that that major limb has to go so it won’t hit the roof/wall/door”. “I need to have this 14 inch limb removed 10 feet up in this 60 foot maple tree”. What I would like to reply is “Can you move the garage over to the other side of the property where there are no trees? “ But not wanting to come off as a smart Alec I will try to explain the consequences.

Making major cuts on the main stem of a healthy tree opens the trunk up to invasion by wood decay organisms and creates structural instability in the entire tree. Trees prevent decay by compartmentalizing the damaged wood. They produce rot resistant barriers using chemicals that the tree fabricates at considerable expense. The tree doesn’t head out to the hardware store and buy turpentine or stain it literally makes it! It doesn’t put it all on the credit card either however it uses its precious energy stores to create these protective bio chemicals. Then it concentrates these protectors in cells near the injury. Once these cells have been used as protective barriers they die and become nonfunctional to the tree. It is a very energy expensive process. These protective zones can be hundreds or even thousands of cells deep. They disrupt the normal flow of nutrients and the tree has to grow over them to close the wound. This will take many years and when it has grown over, the tree will have a large hidden defect that can break unexpectedly. The results can be catastrophic not only for the tree but for the structure that has been built so close to the compromised tree.

There is good evidence and many studies that also show that the removal of large limbs causes internal stress that can crack the interior wood of the tree and weaken its structural integrity. In nature major limbs rarely break and when they do as a result of extraordinary force, they break far away from the trunk and prevent decay from entering the main stem. Many times after storms the trees that fail are ones that have been pruned drastically low on the trunk in the past. Please consider all the options, including complete removal, before making these types of cuts. The practice of painting wounds is not first aid and would require an entire article to explain why it often does more harm than good.

If you are considering construction close to mature trees contact your ISA Certified Arborist to develop comprehensive pruning plan.

Monday 15 August 2011

Circled Roots

I spend the majority of my time examining trees. And I really like that! However lately I have been noticing more and more trees with circled or girdling roots. The outward expression of this condition can be very obvious, a large root or group of roots circling a tree above the surface of the soil quite clearly strangling the life out of the tree above. Or it can be practically un-noticeable, a buried root that circles around below the soil level choking the life out of a seemingly healthy tree. And the signs can also include thinning tree crown and eventually die back. Trees generally have a pronounced widening at the point where they enter the ground, called the basal flare. The tissue at the base of the tree is a mixture of trunk tissue and root tissue that is very tough and resistant to insects and decay. If you have ever burned piece of a stump it takes forever. If you have tried to chop a stump out with an axe you will know how tough this tissue is. In fact one of the most common ways to remove a stump is to grind it out like you would grind a rock.

Root tissue is different from this transitional trunk flare tissue and will not join or graft to it when they come in contact. When the root tissue tries to grow over the trunk tissue, the tissues continue to expand compressing the trunk tissue. The phloem in the trunk tissue, the outermost layer of living cells is responsible for transporting sugars back down to the roots from the leaves where it if produced. The phloem becomes blocked and compressed by the root pressing against it and results in further swelling above the blockage. This continues until the tree completely blocks itself or the root is removed.

This past weekend I purchased a Japanese black pine on a standard, while I was planting it I discovered several girdling roots. Fortunately they were small and I was able to remove them with a pair of pruners while I was planting it.

The lesson learned is that even small trees can have potentially large problems. You must carefully examine their roots and take corrective actions. Roots should move away from the trunk in a pattern resembling the spokes of a wheel. If they circle back or cross other roots sideways to the trunk, problems may be looming.

Three seasons ago we were able to identify a potentially fatal root conflict on a Dawn redwood. We were able to excavate the root collar with high pressure air and carefully remove the root. Typically the results are slow to show, however this particular redwood made such a remarkable recovery, you can barely see where the root was circling the trunk. If appropriate timely action is taken the problem can be averted and the trees life extended.

If you have trees with troubled roots contact your ISA Certified Arborist to develop a root recovery plan.