Two kinds of strangler fig grow along Ourimbah Creek: the small-leafed fig Ficus obliqua that grows on rocks and trees, and the rusty fig F. rubiginosa that is more usually confined to rocks. The problem is how to get them to regenerate into the big trees that support epiphytic orchids, ferns and interlacing lianas - how to revive their key role that they once had here as an ecosystem of mutually-dependent species.
Fig trees take a human lifetime to regenerate naturally, because they have to start life as seedlings high up in the canopy, often germinating in the debris accumulated by elkhorn ferns. Then it takes many years for their roots to creep down the trunk of the host tree to ground level. Only then can they start growing quickly, with their roots in the ground and their leaves collecting light high up in the canopy. However, we can speed things up.
The surviving trees that in our valley produce thousands of fruit, each one with hundreds of seeds. Possums love to eat these fruit. So, to harvest the seed, we just need to sweep up their droppings from under a mature tree. The droppings are not smelly, and consist mostly of fig seeds, nicely cleaned by the possum digestive system so that they are ready for sowing.
Raising fig seedlings is easy. Just sow them on the surface of seed compost and supply them with plenty of water and fertiliser. It will soon become apparent that their roots show a marked tendency to grow downwards, often attaching themselves to supports in much the same way as do the roots of epiphytic orchids. But, like orchids, they need a humid atmosphere so that these aerial roots are protected from drying out.
Here, fig seedlings have been tied to hardwood stakes and their roots protected with elkhorn fern. While growing like this they make a living screen for our balcony. The long roots are accommodated in pots at the base but, before they reach the pots, daily watering is needed.
Strangler fig seedlings usually germinate in trees. The one pictured below germinated in the rotten base of a branch which had broken from a Sydney blue gum (Eucalyptus saligna) about 20 m up. After existing several years as an epiphyte, it sent out aerial roots that eventually reached the ground. Once that happened, the seedling grew many more roots that encircled the tree. Already, these roots have begun to join up and will eventually form a solid trunk around the original tree. The stage shown here may be thirty or so years after the original seed germinated.
Years into the future, this fig tree will have a huge canopy that will be host to many other plants and animals. Not a tree for the average back garden, perhaps, but a great home for native fauna.
The main thing to bear in mind when strangler figs are grown in a nursery is that their long naked roots are vulnerable to drying out. However, if they are protected and surrounded by a humid atmosphere, these aerial roots keep growing steadily downwards. The longer they are allowed grow, the higher up in a host tree the plant can be attached. That enables the lower ends of the roots to access moisture and nutrients in the ground, and the plant can grow rapidly. Once they attain this stage, with roots in the ground, strangler figs are remarkably resistant to drought.
Here's a fig that was grown on a pole while gently coaxing its roots downwards. Drip irrigation with dilute hydroponic solution helped to keep the growing roots moist while supplying the nutrients needed for growth. The kind manufactured for growing hydroponic strawberries works well for this.
The photo was taken (November 2012) after attaching the plant to the trunk of Maiden's wattle (Acacia maidenii) and planting the lower root ball in a pile of leaf mulch. Now (May 2014) fig roots are growing around the supporting tree. How will it look in 10 year's time?