Ficus: a rare Genus: part 1

Fig 1: Ficus macrophylla – Moreton Bay Fig – in Conondale National Park in SE Queensland. This ancient tree, estimated as being at least 400 years old, featured in an AAA arboricultural study and past article entitled The Body Language of an Ancient Sentinel, Part 2 in the April/May 2022 issue. The tree measures 50m x 57m, with a six-metre DBH. Based on its body language, it started life as a strangler fig on a host tree prior to forest clearing in the 1850s and subsequently engulfed the host, establishing itself as a field-pasture tree prior to the forest’s regeneration. This image is a testament to the genus in its natural forest environment. Image; Cassian Humphreys

Ficus offers a unique opportunity for land care, says Cassian Humphreys.

Arboriculture, as most of us know it, is founded on what we are taught. The experience of trees adds a far greater dimension. Our experience is usually driven by a specific genus most common to the geographical regions we work. Few of us in Australia can travel far without experience of Eucalyptus or Corymbia – although, currently being back in south-east Queensland, l’m focused on fig trees.

The subtropical and tropical genus of ficus is certainly king to many regions of the east coast and the far north of Australia.

Fig trees are specialists

Arboriculture as a service-based profession is best driven by what trees embody (as opposed to an industry prerogative) and how they interact with their environment.

When l look at ficus l see an underutilised opportunity for arboriculture and the land-care movement. The purpose of this article is to consider the body language of this genus, and how we can adapt arboriculture to accommodate the benefits of the many species of fig. Mainstream arb or land capacity of this genus.

With sufficient vitality, most trees as generating organisms have the potential to occlude and compartmentalise any other body, including their own. Bodily regeneration is the miracle of the world’s Phoenix trees, of which ficus as a strangler is legend.

Some trees will engulf whole buildings. Fig trees are specialists.

The Bohdi trees (Ficus religiosa) of Angkor Wat in the ancient temple complex of Cambodia are a classic example (a very worthy Google). Consider the natural regeneration of the forest in the city of Chernobyl, Ukraine. Following the nuclear disaster of 1986, nature gives us a glimpse of the far greater capacity for ficus in service to the tropics. The ancient Indonesian fig tree suspension bridges (fig trees spliced together by man to support ancient thoroughfares) are another marvel of the genus.

Fig 2: A typical root buttress associated with the ficus genus, the perfect example of a new tree over a long-entombed host. They’re the ideal means to replacing weed species like camphor laurel on creek systems. Image: Cassian Humphreys

Unique study

Based on nature, the best way to replace many east coast trees is via ficus species, particularly weed trees on creek systems. Rather than the costly financial and environmental removal of large trees like camphor laurels, opening up creek systems to erosion, how easy in comparison is it to install ficus species as stranglers.

Ficus as a genus is a unique arboricultural study. Made up of 850 different species in the family Moraceae with few species living outside of the tropical zone, Ficus carica (the cultivated edible) from Southeast Asia to the Mediterranean, is one of the few temperate trees of this genus. In Australia there are 11 well-known natives, eight of which have good capacity to entirely engulf host bodies as stranglers. The native or naturalised species of ficus in Queensland in order of commonality in my experience are:
• F. obliqua (Small-leaved Fig)
• F. macrophylla (Moreton Bay Fig)
• F. benjimina (Weeping Fig, naturalised in the far north)
• F. microphylla var hillii (Hills Fig)
• F. virens (White Fig)
• F. microcarpa (Curtain Fig)
• F. henneana (Deciduous Fig, formerly a variant of superba)
• F. coronata, fraserii, oppositifolia (smaller species, non-stranglers), and
• F. platypoda (Rock Fig).

As well as the natives, the exotics consistently found in Greater Brisbane are F. religiosa, F. lyrata, F. elastica, and Ficus benghalensis.

Fig 3: F. benghalensis – a Banyan Fig – in Roma Street parkland. Most fig trees are stranglers without prompting, spreading vegetally via aerial root props. Planted figs grown as field-pasture trees do not always produce aerial roots as part of their generation (this, for some, seems to be a greater trait in the wild). The Indian Banyan Fig is a testament to such production. This tree well illustrates how we can help induce such growth. Inducing prop generation is now a horticultural practice in Roma Street Parkland. Graft and prop inducement should be mainstream arboricultural training. Image: Cassian Humphreys

Distinctive traits

Off the top of my head, the attributes that set this genus apart are:

1. They’re exceptional performers subject to good vigour* – meaning a genetic predisposition for longevity, especially when subject to good vitality, with health based on optimal environmental conditions
2. They have the exceptional capacity of natural graft unions involving aerial prop roots between trunks, branches, and leaders, as well as prop roots to ground (rocks and soils), and they’re masters of vegetative propagation
3. They are exceptional producers of tree-muscle or reactive wood adapted to load, also known as ‘flexure wood’. Where most broad-leaved trees tend to produce tension wood, figs are adept at generating both tension and compression wood, creating horseshoe-type growth formations above and below branches and roots – or figure eights in their body language. The optimisation of long, lateral limbs in ficus is legendary, where compression and tension wood combined create I-beams, an exceptional form of optimisation (ref: Fig 4).
4. Ficus creates a very strong boundary zone or Wall 4 separating new wood from old, and
5. They have an excellent capacity to transition from forest trees into fieldpasture trees.

Weaknesses

The ‘weaknesses’ in this genus as compared to other genera are perhaps weak resistance zones (Walls 1-3), which enable cylindrical decay. Though the strong boundary zone (4) coupled with aerial root production and natural graft formation more than makes up for outer wall optimisation, it can be well argued that losing internal ballast serves figs perfectly. Subject to stress and poor vitality, fig trees can be prone to failure at the root crown via Phellinus noxious and Ganoderma fungal-decay species. Though in healthy friable soils subject to high species diverse forest microbiology (where below ground the good guys compartmentalise the bad guys), with good vitality the figs outgrow the fungal decay pockets and columns, benefiting from the associated trunk hollows. At an advanced age they generate roots back into open cavities.

Fig 4: F. virens is another ancient tree from AAA, December/January 2021, The Body Language of an Ancient Sentinel, Part 1. This fig tree was one of the most interesting VTA studies of my career. The heavily muscled, 22m horizontal limb with pronounced tension and compression wood (classic I-beam or figure 8) had these vast ropes of reaction wood acting as giant star-wheel braces situated either side of the branch. I have never seen examples of such optimisation on younger figs before or since. Image Cassian Humphreys

Ficus future

Already a horticulturist, I started my early career with the awareness of bonsai. Back in the very early 1990s I had the pleasure of knowing a British Merrist Wood arboriculturist and bonsai specialist, Noddy Knott. At the time I didn’t realise that art as being a solid foundation to the culture of trees regardless of size. A lifetime in arb has bought me full circle. Between treating the top end of the pump, or pinching out the tips (buds) for crown subordination, to treating the bottom end for a healthy, nutrient-absorbing interface, bonsai is the perfect illustration for arboriculture.

Talking of horticulture, the old practice of the inducement of natural grafts fits bonsai as well as advanced, aged trees, and particularly fits the ficus genus.

In a future article I’ll have a closer look at this practice as a means to illustrate arboricultural service adapting to better accommodate the genus. It’s a practice with similar parallels to assisting young, professionally installed fig trees to grow on and strangle trees we designate as hosts, mirroring nature’s strategy.

One thing is for certain, with scientific talk of Earth’s predicted next mass extinction event (there have been five already on the scientific record), as with the reforestation of Chernobyl, a city like Brisbane will certainly play host to ficus species. Here is praying we arborists get to be part of the solution that facilitates the new Earth, by mass planting ficus in our cities to prevent such an event from ever happening.

Fig 5: In ficus species, the development of fungal decay cavities and columns (ref: fruiting body at centre) targeting the ‘past’ tree are well optimised by the generation of flexure wood and the cascade of aerial root ropes and props. Making up the ‘now’ tree, such growth continues to gain great ground in tree structure, far outgrowing any losses to decay. Image: Cassian Humphreys

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