1

Veteran tree risk management via reduction,

nutrition and exclusion

Part 1 – Background Edited by Karyn Szulc (QAA Executive Officer)

Introduction

This article coincides with the development of my most recent QAA Workshop

Advanced Pruning for Veteran trees (scheduled for Cleveland 26/6), which like

this article involves the consideration of reduction, exclusion and nutrition

acting as sustainable risk management strategies over whole tree removal.

In part 3 of this article I also consider the benefits of support as a means to risk

management and look at a solution to Australia’s general resistance to the

installation of fall arrest systems in trees.

Historically the collective tree profession has largely looked at tree removal as

being the only applicable risk management strategy to use for veteran trees (if a

veteran tree can not be pruned to standard it is cut down). Many amongst the

climbing arborist sector will gladly remove a tree with ‘defect’ symptoms using

that as reason for pulling out a chainsaw as a means to abate the risk.

In reality most of the kinds of trees that fail are those that are already falling

apart and are far from being safe to climb at all. In fact it is easier to safely retain

veteran trees at reduced financial cost and gain to the environment (that relies

on trees) by reduction, nutrition and exclusion.

Before we can get serious about managing veteran trees we must recognise how

they naturally adapt to the environment, to the mechanical failure of their

bodies. Veteran tree adaption or optimisation is a process predating the

evolution of people-kind, in our bid to manage trees we surmount tree time with

our time and forget this. We become lost in our perception of the ‘defective’, our

misunderstanding of the process of tree self-optimisation, whilst forgetting to

look at all the trees that have not failed.

2

Plant growth & Epicormic/Endocormic growth transition in Trees

A rudimentary glance at the growth of plants tells us that limbs are grown from

immature shoots or buds. Scientifically buds are categorised by location, status,

morphology and function.

Fig 1

Buds are located either at the end of a stem via a terminal bud or at the sides

(lateral or axillary bud) of a stem. Axillary buds are formed at nodes (the base of

leaf axils) and internodal locations on plant stems via adventitious buds.

Adventitious buds are buds (which likewise grow lateral to the parent limb) that

are formed on the trunks and roots of woody plants. When a leader or branch is

damaged or removed (e.g. by people or the environment) and the lateral branch

suppressant hormone auxin (is temporarily lost with the terminal growing

point) adventitious buds (dormant and newly formed) grow producing shoots,

which like axillary buds become woody limbs following incremental secondary

growth.

Fig 2

Epicormic shoots (Camphor laurel)

Axillary buds (which grow from leaf axils with a bud trace) are considered by

most in higher arboricultural education to produce stronger limbs than those

that have grown adventitiously (I would like to see a study explaining why).

Determining whether a limb has grown from an axillary or an adventitious bud is

seldom possible in an advanced age tree. However a limb, which has grown

sufficient increments of wood (into the parent stem) or has a sufficient diameter

in proportion to its height (H/D) is known (by the principles behind VTA) to be

stable in the same way that a limb grown from an axillary bud is stable (held in

place by multi laminations of wood).

3

If epicormic (a well established arboricultural term) limbs are born from

adventitious buds, then what do axillary buds grow into?

We have all grown up with the use of the term epicormic, Latin for Upon the

Stem (Epi – Upon, Cormic – Stem), we have all grown up with advice on the

defective nature of epicormic limbs.

So what is the name or term for the opposite of epicormic? This question is

something that has long bugged me since my initial Arboricultural UK (Merrist

Wood) education (90-92).

Following a major report that I prepared for Energex on the 2008 Brisbane Gap

Storm (and past AA article - Ref ETS/Energex 2008 Gap Storm Report –

Aug/Sept edition AA 2009) I invented a new term to both fill the void in (my)

arboricultural understanding and offer explanation for why so many of the

‘epicormic’ branches that I had condemned survived the storm. That term is

Endocormic – Latin for Within the Stem (Endo – Within).

I have been using this term professionally ever since, though it was not until an

AA publication (2012) by Gail Bruce (Arboricultural Journalist) on Scott Hanley's

past QAA Advanced pruning workshop that I saw the term used by another

leading Qld Arboricultural professional.

Though regardless what we humans think, the trees are physically growing and

adapting to the environment via the growth of axillary, adventitious buds,

secondary growth (the laying down of wood increments) and

epicormic/endocormic type advancement.

Fig 3 Fig 4 Epicormic - Latin for ‘upon the stem’ Endocormic – Latin for ‘within the stem’

Fig 5 Fig 6

Fig 5 - Epicormic growth branch break out failure due to insufficient wood

laminations and Fig 6 - Endocormic growth tension failure with sufficient wood

laminations – Note failures caused by hand

Ref ETS/Energex 2008 Gap Storm Report – Aug/Sept edition AA 2009

4

Study of many urban-forested city environments will yield numerous examples

of trees that where veteranised by storms or tree loppers that have since

adapted and succeeded.

The pioneers in UK Veteran tree management (Neville Fay - Tree Work

Environmental Practice) have posed that storm damaged trees better adapt to

their veteranisation than flat topped trees (by chainsaw), this has lead to natural

fracture pruning practices being employed in UK conservation arboriculture.

Fig 7 Fig 8 Natural fracture pruning practice (courtesy of Andrew Cowan) now a part of

Conservation Arboriculture UK

We know that topping trees is destructive, that topped trees (by storm or

lopper) are certainly compromised, though do we recognise that many veteran

trees adapt damaged crowns into stable functioning replacements - via the

growth of buds and laminations of wood? Many experienced arborists in

arboriculture agree that there are more veteran trees that adapt and succeed

(for years) following veteranisation than those that fail.

Arboricultural experience shows us that those trees that best adapt to crown

failure are those that lose smaller diameter branches as a means to mitigate

wind force (assuming that crown harmonics – the trees natural ability to diffuse

force flow is overcome). Though there are also numerous trees that lose large

diameter branches and make subsequent crown adaptions that keep them alive

for many years.

Regardless of a trees age its success is driven by vitality, which is driven by its

ability to successfully photosynthesise, draw nutrients (elements) and water.

Where we witness excellent signs of adaption involving the generation of

replacement crowns, wound occlusion, reaction wood development and

compartmentalisation then we know that we either have a healthy tree (health

or vitality is driven by a compatible growing environment) or a vigorous tree

(which is driven by a strong genetic code) to quote Shigo (or both).

5

The fact is that the shedding of small diameter branches (25mm<) or even just

leaves, as a means to dissipate wind force is a part of the trees natural success

story. Though we fail to notice the leaf litter, the downed small diameter

branches and the still standing trees after a storm event (favoring observation of

the dramatic – the big and the broken).

The reason that trees easily adapt to light crown failures is simple – 1) due to the

numerous dormant and adventitious buds that are located all over the stems of

young limbs. And 2) because of the ease of adaption that epicormic shoots have

on small diameter branches (subject to some tree species variation – i.e.

Camphor laurel trees produce better epicormic growth from larger diameter

branch stubs) – with the growth of wood laminations they become endocormic

very quickly.

Fig 9

Fig 9 – Refers to a study of any of Britain’s famous 1000 year+ ancient oak trees

(as with this one from Meetings with Remarkable Trees by Thomas Pakenham)

which Illustrates self-optimisation and crown ‘re-configuration’ (via growth of

dormant buds and wood increments) following historical loss perfectly.

In the natural environment trees are generally regarded to have 3 phases to their

lifespan – upward/outward growth, a sustained functional rest (without

significant growth expansion), then a slow downward decline (or retrenchment)

with subsequent generation of a lower/internal crown. However in the urban

forest due to our non-sustainable interaction with the environment (largely

caused by a hard landscape foot-print) and demands for space trees seldom live

beyond the first phase. Yet with arboricultural management (reduction, nutrition

and exclusion) there is no reason why old aged and veteranised trees can’t be

sustainably retained and managed into the final chapter of their lifespans.

6

Thanks to the contribution of UK Veteran tree management

researchers/practitioners (Neville Fay, Ted Green, Jill Butler & Andrew Cowan)

we have records such as the 99-year-old photographic history of the Arthur

Clough Oak.

Fig 10

This historic trees adaption (courtesy – Andrew Cowan Arbor Ecology UK) from

a forest to field pasture tree via crown loss - crown retrenchment - dieback and

transition from an epicormic to endocormic crown is well recorded in 5

photographs spanning 1910 to 2009.

Since the 2008 ISAAC Brisbane seminars on Veteran trees (Ted Green, Jill Butler,

David Lonsdale & Andrew Cowan) I have been looking for and finding the same

traits of transition in our Australian veteran trees.

My well-travelled VTA course (VTA an Australian Perspective) covers a large

amount of local photographic data supporting the transition of epicormic to

endocormic (a small sample of them feature in this article).

It sadly is to often that the case of one limb failure that leads to human tragedy

will fuel the felling of hundreds of trees that have no past history or imminent

likelihood of limb failure. Limb failures occur based on stressors in the internal

and external tree environment, naturally the outside environment influences the

trees internal environment. Figs 11 & 12 are photographs of limbs, which have

made the transition.

Fig 11 Fig 12

7

Fig 13

Fig 13 is a classic example of a veteran Gum (E. crebra) that has generated a

substitute crown of epicormic branches (already transitioning and restoring

crown harmonics) following a historic crown failure.

Based on my 5.5 years (2007-12) of assessing large Gum tree populations

extending south to north from Central West Brisbane to Tin Can Bay and west to

east from Esk to Bribie Island (the Energex VTA Program) my experience of

epi/endo crowns and limb failure has validated my hypothesis (that trees

transition). The Gums by measure of population, time duration (of appraisal) and

record of electrical outage are considerably more prone to succeeding than they

are failing. Of the Gums that had the most major crown failures in S.E. Qld (with

mechanical constraints or defects) E. grandis and E. signata where the most

common (but still not significant in number).

Fig 14 Fig 15

As with all trees where there is sufficient vitality (resources to grow) and

sufficient diameter (foundation) in proportion to height (stable structure) trees

succeed. Considering the amount of resources that the epicormic branch in Fig

14 (E. tereticornis) must use to generate a sufficiently stable footprint (to

occlude/compartmentalise the severed codominant limb and then to generate

sufficient increments of wood around that limb) then this would be a major feat

on behalf of the tree (though with sufficient vitality not impossible).

Whereas considering the resources and diameter growth necessary for the

epicormic branches in Fig 15 (Cinnamomum camphora) to succeed then failure

is not much of a consideration (unrecorded on Camphor laurel in Toowoomba by

Toowoomba Regional Council).

8

Epicormic limb failure is mostly based on branch breakout failure (as with Fig 5)

or failure akin to bifurcation failure, though other factors may influence (fungi

induced wood embrittlement or fungi induced wood softening) but failure is

always based on a lack of diameter to support height or length.

Another major career learning opportunity for me has involved working on the

Camphor laurel lined street Trees of Toowoomba (a small rural City West of

Brisbane), between 1996 to 2001 as a contractor I pruned at least 3 thousand

Street and Park trees. Then in 2003 I was commissioned to prepare a vegetation

management review and report (as a part of a MOU between the Council and the

Utility managers Ergon) on a sustainable approach to managing Toowoomba’s

historic avenues of Camphor laurels.

These trees had been topped at least 5 times in their lifespans going back to the

1930’s, though this as a practice had stopped by the early 90’s, all the Camphor

lined streets are made up of veteranised trees (as with the Brisbane historic

avenues of Camphor laurel). The camphors being vigorous large woody trees

growing in highly fertile volcanic soils (in a cold winter climate) have adapted to

topping and root severence/butress root grinding (due to footpath lifting/trip

hazards) in ways better than any species of tree I have witnessed (bar the

Australian Red Cedar). It was learning from these trees that I first recognised

epicormic to endocormic type crown adaptions.

Figs 16-19 show varying stages of Epicormic to Endocormic transition on

Camphor laurel trees (Anzac Street New Town)

Fig 16 Fig 17

Fig 18 Fig 19

The photographed stages of growth (akin to wood growth associated with lapsed

pollards in the UK) range from 5 to 25 years of the generation of wood

increments over the original epicormic shoots linking into the trees parent

stems.

9

Photographs (Figs) 20 – 23 show leaders/limbs which where cut internodally

and grew subsequent epicormic shoots, which generated into replacement limbs.

Fig 20 Fig 21 Fig 22 In Fig 20 we can clearly see the incremental circles of wound wood via the bark

pattern around the end of the occluding remnant (hollow) parent limb. In Figs

21, 22 and 23 we can likewise clearly see the ends of the occluded parent limbs

through the bark of the adapted endocormic branches/replacement leaders.

These epi/endo crown adaption samples are all of Camphor laurel, bar Fig 22

which is Grey Gum (E. propinqua) and are all excellent examples of significant

vigour and vitality.

Fig 23

A study of any one of the hundreds of Toowoomba’s veteran Camphor laurel

trees validates these observations. Contained with-in my VTA presentation I

have numerous other examples of this and similar traits that are unique to

Australia.

10

Conclusion

Part 1 of this article sets the stage as the background to the Reduction

component to a 3-part piece, which is a study of the risk management options

that are available to us for veteran trees. The current Australia standard for the

pruning of amenity trees does not cover sustainable veteran tree management

via pruning. In Part 2 of this article I will be posing a well considered, supported

(US, CAN, UK) and trailed approach to advanced pruning for veteran trees. It

must be stated at this point that my promotion of veteran tree management (and

the recognition of transition from Epicormic to Endocormic) does nothing to

take away anything from AS/4373 but adds to it.

Of the Genus and species of tree that I have consistently observed that have

successfully made the transition from Epicormic to Endocormic (without failure

to minimal failure) throughout S.E. Qld – those are Camphor Laurel -

Cinnamomum camphora, Jacaranda - Jacaranda mimosifolia, Chinese elm – Celtis

sinensis, Grey gums - Eucalyptus major, propinqua & biturbinata, Corymbia -

Corymbia citriodora maculata, C. henryi, C. tessallaris, Blood woods – C.

intermedia, C. trachypholia, Brush box - Lophostemon confurtus, Forest red Gum -

Eucalyptus tereticornis, Blue Gum - E. saligna, Iron Barks - E. crebra, E. fibrosa,

White maghogany – E. carnea, E. umbra & E. acmenoides. Perhaps one of the most

dynamic examples I have observed of the transition is with examples of the

Genus Ficus where aerial roots are employed to graft epi/endo crowns to the

parent crown (more epi/endo examples to come in Part 3).

These are off the top of my head, the list goes on. Regardless of tree Genus or

species the reciepe of success for trees that succed in general is vitality. This is

especially so to enable trees the transition of epicormic to stable endocormic

crown structure, it is the arborists job to inspect those unions to determine

stability as part of a risk management plan (the UK - ITMP is covered in part 3).

While I accept that tree species with weaker vigour (gene codes) and poor

vitality will not make the transition (without sucumbing to death or structural

failure), those tree species and trees that do need to be recognised by us as

veteran trees worthy of retention and risk management.

In part 2 of Veteran tree risk management via reduction, nutrition and exclusion

we will explore a financially and environmentally sustainable means to achieving

veteran tree risk management via Reduction. This strategy is by no means a new

one to arboriculture though historically the practice has done more to reduce

tree lifespans than promote them. In my last Arbor Age article I made reference

to the 5/30 rule as a directive to sustainably reduce the crowns of trees. This is

to be explained based on a veteran tree management project and report that I

developed in my last senior arborist role. Knowing the hands on approach that

most arborists have (including me) I generally like to use an actual job to

illustrate the reason behind my articles.

Thanks, with regards to all in arboriculture – Cassian.