Tree education for you.
Check out our visual dictionary below ….
Bifurcation
is defined as the process of division of roots or branches at one end into two parts.
The image is of a tree we inspected for a client, the trunk bifurcates approximately 500mm from the base of the tree forming two trunks. In this instance the bifurcated union is acute and as the tree has grown, included bark has developed. Swelling on the lower trunk is indicative of internal decay and the tree is at risk of failure whereby the compressive forces in the fork when exposed to storm or high wind events are prone to failure.
Selective pruning practices when the tree was juvenile to remove one of the trunks could have eliminated the structural concerns and enabled the tree to be retained.
Braided reaction wood
Also referred to as ‘Adaptive wood’ or ‘Reaction wood’ is defined as additional load-bearing wood formed in response to mechanical stresses and gravitational force upon the vascular cambium to provide a uniform distribution of loading. (Danny B Draper, Peter A Richards - Dictionary for Managing Trees in Urban Environments)
The image shown is of a tree we assessed for our client. The braided reaction wood was noted on the scaffold limbs and smaller branches. Trees are subjected forces. Claus Mattheck refers to three forces in his book ‘The Body Language of Trees’, tensile force (gravity) is defined as pulling a component lengthwise generating tensile stresses. A compressive force though compresses the component but is limited by compressive stresses within the component.
Bending is defined as a force applied to the trunk of a tree crosswise as a lever arm, bending the trunk. On one side there are tensile forces and on the other compression forces.
Torsion force is when a force is applied crosswise to a side branch (wind), you will see the branch bending, the trunk to which the branch, or lateral lever arm, is connected is also bent but additionally twisted. (Claus Mattheck - The Body Language of Trees, pg 22) Shear wounds can result in what looks like the limbs being torn from a tree.
The Braided reaction wood is the development of adaptive wood to withstand the various forces listed above, providing greater resilience and structural integrity.
defined as a branch collar continuing to develop around the remains of a dead branch.
In the image shown, the branch failed, possibly as a result of storm damage, and the remaining section of branch died. You can see at the base of the branch the live section of the branch that continues to grow around the dead branch. In this instance we would recommend selective pruning of the branch to remove the dead stub and give the tree the opportunity to compartmentalise the wound. If the branch is left in its present state, the limb will deteriorate and there is the risk of this limb failing or the tree will be exposed to pests/diseases and placing the health of the tree at risk. In instances where there is evidence of a good habitat hollow in the stub, we will prune it back to minimise the risk of limb failure but also enable the limb to be used as a habitat hollow.
Trees develop collars as they grow as a mechanism of separating the trunk from the stem if the branch died. Every year the new growth envelopes the existing branch collar, within this collar a tree develops a protection zone that contain antimicrobial substances, when a branch dies the branch inhibiting organisms (decay/dieback) grow downwards towards the collar, the protection zone restricts the access of these organisms into the trunk effectively stopping the decay at the collar. (Alex Shigo - A New Tree Biology, pg 13).
Compartmentalise is the process with which a tree seals a wound following damage sustained, to ‘wall off’ infected areas of damage in an effort to maintain and restore structural support.
The CODIT principle (Compartmentalisation of Decay In Trees) - Alex Shigo, is the process of protection that a tree initiates at the time of injury or infection. The principle has four ‘walls’, these are simply classified as - the first wall resists the vertical spread, the second wall resists the inward spread and the third wall resists the lateral spread of infected wood. The fourth wall is the strongest that separates the tissue present at the time of wounding from the tissue that forms after.
The image shown is of a pruning wound sustained several years prior to the photo being taken. When the tree identifies that it has been wounded (whether a pruning wound or a pest attempting to penetrate the tree) the initial response is a chemical response whereby the tree places a chemical seal over the wound (the smaller the wound the more efficient this process will be) effectively plugging the vessels. The second wall is the dense late wood located at the outer edge of an annual ring, this can delay the inward spread of pathogens or decay. The third wall are the wood rays which work to impede the lateral spread of decay. The fourth and strongest wall is both an anatomical and chemical wall that develops to conceal the wound. This process referred to as Occlusion encloses the wound face, concealing the wound and restoring the growing surface.
The definition of co-dominant is where two or more first order structural branches or lower order branches of similar dimensions arising from about the same position from a trunk or stem.
Each co-dominant is a direct extension of the stem below its origin (Alex Shigo, A New Tree Biology, pg 22). If the union where the branches extend from is separated by Included Bark then the union is considered weak and prone to failure, particularly in storm events. At the base of the co-dominant stems there is no branch or trunk collar and no protection zone that you would find at the base of a branch that work as a mechanism to protect the tree from the spread of pathogens into the trunk.
Ideally a tree should have a central trunk (leader) with a balanced canopy (crown), in instances where co-dominant trunks form the canopy, they compete and can result in the canopy becoming over-crowded and unbalanced.
Formative or selective pruning while a tree is juvenile, or when the issue is noted, would be recommended to remove or reduce the co-dominant branch to better enable the main trunk to develop.
A Compression fork is a fork formed where two stems with an acute branch crotch grow pressing against each other with included bark which becomes enclosed bark, where the stems flatten at their interface under increasing compression from each successive growth increment, forming a weak graft as a welded fork which remains susceptible to tensile stress (Mattheck & Breloar 1994, pg60).
In the image shown the trunk bifurcates with the main trunk and co-dominant trunk growing with an acute crotch. Included bark is noted, you can see the swelling towards the lower region of the union. This swelling is referred to as ‘Elephant Ears’ and is suggestive of the tree attempting to stabilise itself. A compression fork is prone to failure as the trunks grow pressing or pushing against one another, the region of included bark developing internal decay exposes the tree to stresses, particularly in storm events, resulting in the failure of one of the branches/ trunks.
Formative or Selective pruning practices at a juvenile age, or when identified, could have eliminated the risk of failure by removing the codominant. The wound would have been minimal in size, compared to the wound size in its current situation, and the tree would have compartmentalised the wound with occluding tissue enclosing the wound face, concealing the wound and restoring the growing surface.
is defined as branches or roots forming a point of contact where they grow over each other. Such contacts may form a graft, or may form a mechanical abrasion wound in branches subject to movement. (Danny B. Draper & Peter A. Richards - Dictionary for Managing Trees in Urban Environments).
The image shown is of a large Corymbia citriodora (Lemon Scented Gum) that we assessed for our client. The branches were noted as crossing over, the rubbing of the branches creates a wound that exposes the tree to pests or diseases being able to infect the tree. Additionally, the structural integrity of the branches are compromised predisposing the tree to limb failure. In some species the cross-over branches can become ‘grafted’, this union develops into a permanent union sharing vascular functions and structural loading. In this instance, the grafted unions would be retained and not removed through selective pruning practices.
Selective pruning practices to remove cross over branches where it is evident that mechanical abrasions have caused structural damage to the branches, ecan eliminate the risk both with the structural integrity and with pests/ diseases.
is defined as the process of wood degradation by micro-organisms (Australian Standard AS4373-2007) and fungus.
Decaying is the process whereby there are active pathogens in the wood. Decayed is the result of the wood changed by the pathogens.
The process of decaying commences immediately after the tree has been wounded. The highly ordered wood and processes in the wood are suddenly disrupted as a force from outside the tree begins to affect the processes of the inside of the tree. (Alex Shigo - A New Tree Biology, pg 33).
The image shown is of a tree we assessed for our client. The region highlighted as decay resulted from a branch removed several years previous. The tree was not able to occlude the wound due to the size of the branch removed and this resulted in the formation of internal decay within the branch stub, evidence of compartmentalising of the wound was noted but the internal structure of the branch had decayed developing the hollow visible in the image. The tree will need to be assessed as it grows to monitor the progression of the decay into the trunk and the impact on the structural integrity of the tree.
is defined as the death of some areas of the crown. Symptoms are leaf drop, bare twigs, dead branches and tree death, respectively. This can be caused by root damage, root disease, bacterial or fungal canker, severe bark damage, intensive grazing by insects, abrupt changes in growth conditions, drought, water-logging or over-maturity. Dieback often implies reduced resistance, stress or decline which may be temporary.
The image shown is of a tree inspected for a client. Significant dieback was noted throughout the canopy. Foliage loss, twiggy branches and larger wood dieback was observed.
In instances of a healthy tree, selective pruning to remove larger deadwood is undertaken to reduce the risk of limb failure that could damage property or injure people in close proximity to the tree.
also referred to as Round-edged Rib. The definition is: adaptive wood formed over a crack, i.e. branch-bark inclusion or included bark, where the cracking is arrested or slowed by the addition of each new growth increment forming a broad convex swelling. Such ribs may be straight or helical.
The image shown is of a tree inspected for our client, the swelling noted was adjacent to a region of included bark resulting from an acute bifurcation at the lower trunk. The adaptive wood shown in the image developed over many years to reduce the risk of failure.
In this instance, failure would result in the shearing of one trunk effectively splitting the tree in half. No selective pruning could rectify the issues noted and removal of the tree would be the only recourse.
The image to the left shows epicormic regrowth that had developed following the lopping damage sustained by the tree.
Epicormic (Epi - upon) (cormic - stem) (Alex Shigo - A New Tree Biology, pg 43-44) regrowth shown in the image is defined as the development of juvenile shoots from dormant adventitious buds located beneath the bark of a tree. The development of these buds is the trees survival mechanism to the wounding sustained and indicates that the tree is under stress.
The epicormic regrowth in this image is a concern as the shoots that develop are weakly attached to the outer bark and prone to failure as they grow.
Other instances of epicormic regrowth are noted in some species of Eucalypt trees that when exposed to traumatic episodes, such as fire, will develop shoots from latent buds located in epicormic strands that extend from the pith to the outer bark. These are again a survival mechanism of the tree to regenerate the crown. This epicormic regrowth is viewed differently from the shoots detailed in the photo shown, whilst all epicormic regrowth needs to be monitored, the epicormic regrowth extending from lopping damage is more concerning due to the high risk of limb failure and the impact to the health and survival of the tree, sometimes resulting in the premature death or decline in a tree.
is defined as the growth of a root that is not radial away from the trunk or root/s and curves to encircle the trunk or root/s constricting phloem or vascular cambium causing dysfunction.
The image shown is of a tree inspected for our client. When roots are circled such as in the image, as the tree grows and the roots grow they can effectively ‘strangle’ the tree whereby energy from the roots cannot be transported through the phloem to the canopy. Gradually over time the tree will effectively be squeezed to death.
Roots provide mechanical support, they absorb water and essential elements from the soil to store as energy. When girdling roots restrict the flow of energy the tree slowly dies.
Girdling roots can also result in whole tree failure as a result of the inability of the structural root plate to develop and anchor the tree into the surrounding landscape. In storm or high wind events, a tree is exposed to several forces. The tree will bend and twist as a result of these forces and if the structural root plate has anchored the tree into the landscape the tree can withstand these forces. In instances of girdling roots, when exposed to these forces, trees may not be able to withstand the bending and twisting forces and whole tree failure can result.
Hollows form when wood-digesting microorganisms digest all the wood within the boundaries set by the reaction or barrier zone. After a tree is wounded or a branch or root dies, the vertical spread of pathogens proceeds inwards.
The image shown is of a remnant Eucalyptus tree inspected for a tree assessment report for our client. The Goanna identified within the hollow is evidence of the purpose of hollows for fauna and birdlife. This hollow was approximately ten metres from the base of the tree. Through the branch shedding collar, the microorganisms that inhabit dead branches will progress down the branch until they reach the protection zone. Hollows form as the branch shedding collar forms and the pathogens digest the wood.
is related to tree stability, defined as the lifting of one side of a wind rocked root plate or the lifting of pavements and other structures by radial expansion. This can result from the severance of roots, poor root structure or where the soil is too wet. In shrinkable clay soil when it is excessively wet the soil expands and loses its anchoring in the landscape.
The image shows a tree we inspected for our client, the tree was in the process of failing following a wind storm. The surrounding soil was excessively wet and we identified issues with the root structure that suggested there were issues with circling and girdling roots. The combination of excessively wet soil and high winds together with poor anchoring of the root system into the landscape resulted in the failure of the tree.
Have a look at your trees, particularly if there has been consistent rain and the soil is extremely wet. Also anytime we have storm events or high winds, inspect your trees around the base of the tree looking for cracking in the soil or, as in this instance, to see if the tree has a distinctive lean.
(Otherwise referred to as Bark Inclusion) is defined as the accumulation of bark on the inner side of the branch union or within a concave crotch, such as the compression fork in the photo, that overtime result in the formation of internal decay.
As a tree grows it ‘knits’ a new layer of bark over the existing layer, when you have branches that are acute as the one in the photo, the bark cannot knit over the area between the branches and results in the formation of internal decay. The union is weakened and prone to failure as a result. Formative and Selective pruning practices when the tree was a juvenile would have eliminated the structural issue and enabled the tree to be retained. Whilst pruning one co-dominant is an option, the stress and wounding that would result could result in the premature decline or death of the tree.
The image shown is of a tree that was in the process of being ‘lopped’ several years ago. The whole tree was cut to the heights of the branches shown (not by our business). This tree subsequently died.
Lopping is defined as the removal of a top portion of a leader stem (Alex Shigo - A New Tree Biology, pg 114). Lopping involves cutting between branch unions or at internodes on smaller trees with a stub resulting from the final cut. The term ‘lopped’ or ‘lopping’ refers to poor pruning practices that are not in accordance with the Australian Standards AS 4373-2007.
Trees are unable to compartmentalise a lopping wound resulting in the exposure of the tree to pests/ diseases or fungal infestation, further placing the health of the tree at risk.
In the photo shown, the energy reserves held in the branches of the canopy were lost placing significant stress on the health of the tree. The tree used the reserves in its roots to develop epicormic regrowth in an attempt to survive but due to the severity of the damage sustained and the depletion of the trees energy reserves, the tree sadly died.
Lopping irrevocably changes the structure of a tree, increasing the future maintenance costs to maintain any epicormic regrowth and minimise the risk of limb failure resulting in damage to people or property in close proximity to the tree. Under no circumstances are ‘lopping’ practices considered acceptable for pruning a tree.
is defined as Atypical stem growth subsequently influenced and modified by tropisms, i.e. gravitropism and phototropism, where reaction wood attempts to return it to a more typical habit or form.
In the image shown, the growth form of the tree at a juvenile age was modified with the result being that the tree was growing in one direction and then reverted to a more upright direction.
If you have any trees with a self-correcting lean other aspects that should be assessed with the tree include the structural root plate, the trunk for wounding or evidence of adaptive wood growth or internal decay, including fungal fruiting bodies. Trees with a self correcting lean but deemed structurally sound otherwise do not need to be removed, only when structural issues are identified that are likely to result in tree failure would a tree be considered to be removed.
is defined as damage inflicted upon a tree through injury to its living cells where vascular cambium has been damaged by branch breakage, impact or insect attack. Some wounds decay and cause structural deterioration or defects.
The image shown is of a tree inspected for our client. the wounding noted was reported as mechanical damage extending from the two limbs pictured and travelling down the trunk to the base of the tree. Incorrect pruning practices were noted during our inspection which could have contributed to the damage observed.
Compartmentalising of the wound was noted but unfortunately the structural integrity of the tree was compromised resulting in the tree needing to be removed.