Cassian Humphreys follows up from his thoughts in the December/January 2024 issue: ficus offers a unique opportunity for land care.
Since 2021, and after a number of publications on fig trees, I still find my attention on the genus ficus.
In 2022, I, as part of a small team from the Tree Climbers Brotherhood carried out three advanced arboricultural assessments on ancient fig trees. The study included associate understorey and epiphytic plants, though perhaps the most notable plants observed were up to five different species of other young fig trees growing as stranglers.
These past studies were fully recorded in The Australian Arbor Age under the titles The Body Language of an Ancient Sentinel parts 1 and 2 in the Dec/Jan 2021 and April/May 2022 issues. Though I have had a career working on fig trees and observing the genus growing as stranglers on a range of gum trees, I had not seen ficus species growing on Ficus before.
I’ve been planning this article for over a decade, although I was waiting for the right project to document. The prelude to Part 1 involved a past client and the managers of a Brisbane tree company I have long had connections to – Evergreen Tree Care.
Support and nurture
Ficus installation projects have been close to my heart for two decades, although finding clients to support proactive arboriculture is not always easy.
Nature always sets the precedent for we humans, and the growth of Ficus as stranglers spans Queensland and NSW. A past-colleague of mine some years ago predicted arboriculture of the future would become species-specific, specialised to the species of given bio-regions. I can see that this is true of Ficus for much of the central coast and north-east coast of Australia. The capacity for the species of this genus to propagate and generate over existing bodies from buildings to other trees is unique and highly significant. We have no other genera as capable of such feats. As discussed in Part 1, the capacity for the genus to form natural grafts and aerial prop-roots directs us to use the nature of the species to outgrow its own structural limitations. By inducing graft-unions between bifurcations, props on elongated limbs and around decay pockets and columns, we can enable such trees to lay down sufficient wood to outgrow structural constraint, dysfunction and even disease. With Phellinus noxius or Kretzschmaria deusta being common in citified environments we owe it to the fig trees to support them to outgrow their limits – especially when doing so saves money with enduring environmental benefits. Ficus regularly grow aerial roots in association with storm-damage, assisting transition from epicormic to endocormic crown-structure.
Walls
Ficus is known for having a strong Wall 4 – or ‘barrier zone’ to quote Shigo. This the zone which separates new wood from old, and a study of the distinct outer boundary between the creamy healthy wood and the discolored and decaying wood in Figure 2 supports this.
This genus, however, has weaker walls 1 to 3, or resistance-zones, hence the spread of dysfunction up down and across the grain within the barrier zone. Professor Claus Mattheck’s early reference to the 70/30 rule – 70% sound-wood to 30% decayed wood – as a reference to tree retention has fueled decades of misthinking by arborists, many of which still see any less than 30% wall thickness as being the criteria for tree removal. In light of experience with post tree-risk management systems such as QTRA and VALID, many tree-managers globally have redefined that model to 90/10. In the case of Figure 2, healthy wood buttressing in proportion to the decay map, we have 75/25 or 75% decay verses 25% soundwood. Decay which abuts outer-bark between buttresses is a lesser concern, especially when a fig tree lays down aerial-roots outside of that (refer to the red-arrows in Figure 2).
Between such healthy buttressing and the inducement of the prop root I would say this tree with Brittle cinder fungus (Kretzschmaria deusta) was engineered well enough to stand for decades. The tree had already grown an aerial root over a face of diminished wall thickness by its own prompting. I documented the same evidence of aerial-root optimisation in association with Ficus benjamina and Phellinus noxious in the 2012 AAA article Lest We Neglect.
Salute
Imagine if inducing aerial-prop roots to assist fig trees to gain woody ground was mainstream teaching. Such work, along with soil decompaction, mulching and revegetation and Trichoderma inoculation (to help counter aggressive fungi), is, I hope, the future of arboriculture.
The use of round-ended chisels combined with hormonal treatment, as well as sphagnum-moss patching to facilitate graft and aerial-prop-root formation, is likewise arboriculture true to its definition.
Based on discussion posed in this series of articles we have the perfect recipe for sustainable tree management in subtropical and tropical bioregions of Australia and beyond. To my old friend who foresaw the future of arboriculture being driven by bio-region and species, I salute you.
Fast action and a good result
I have a great appreciation of the horticultural works being employed in Roma Street Parkland.
The horticultural strategies of assisted-prop inducement pictured in Part 1 have long needed to be included in the arboricultural repertoire. This, including graft inducement, is a practice of mine going back to my first sphagnum-moss patch on a vandalized Weeping Fig in a Keperra park, Brisbane, in 1995. This was following a lower limb being torn out, leaving a branch breakout injury and a nasty trunk-tear on a tree I had planted myself. The injury I treated via abrading the periphery of the tear with steel wool, dusting the surface with root-hormone powder (I use topgrade honey now), before plugging the injury with sphagnum moss and binding it with grafting tape. This I learnt to do as a horticultural student in the mid 1980s.
Within five weeks the 4cm by 15cm injury site and trunk hole were completely covered by fine aerial roots. Three months later I removed the tape, then another few weeks later I returned to observe the aerial roots desiccated. When I rubbed them vigorously by hand they sloughed off to reveal the wound completely closed by wound wood.
What would have taken between three and five years to close left to its own devices was occluded in less than five months.
Natural progression
Following my getting involved with consulting and report-writing projects with long-serving associates Henk Morgans and Nick Smith, I coincidentally realised their company – Evergreen Tree Care – was the preferred contractor to Roma Street Parkland.
With like minds coming together in association with leading Roma-Street horticulturist Robert Paksec, our first Ficus installation project was supported into creation. We now have a camphor laurel Ficus installation to do.
Initially we established an advanced grown Green leaf Moreton Bay fig (F. watkinsiana) via cage and coir burlaps into a wide fork 10m up the tree. Then we ran a slotted 100mm cellulose/compost/probiotic filled Agline pipe with irrigation line running from ground to the base of the basket, returning to install another pipe running 20m up the tree with a Weeping Fig in a 1.5m compost-filled sock of hessian. All installed by climbers, the pipes were filled at ground-level and hydrated/ activated by immersion in the parkland dam.
The tail of the second pipe was fixed to the ground, providing irrigation to a weeping fig already at ground level. We found a further three native small-leaved figs, (F. obliqua) growing on and in buttress roots. Nature was already showing us the way.
Eye on the future
With the desire to use non-plastic resources I am keen to see the use of coir tubing instead of Agline, the trick being to find a manufacturer to create that. I also recognise the need at intervals along the Agline pipe to make holes, and to tie hessian-bands to help encourage the generation of lateral strangler-roots to help engulf the trunk (we are already booked in to return and do that in July).
The next step with this tree-cultural operation is to promote it to creekland weed-tree managers, to awaken them to the opportunity to use Ficus for such projects. The current practice of removing weed trees, destabilising creek banks, is a very poor strategy.
With Queensland, northern-NSW and sustainable land care in mind, praise be to Ficus and the future of sustainable arboricultural initiatives.