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. Our 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.
They take a human lifetime to regenerate naturally, because they can't grow under the shade of existing trees. Rather, 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 higher up in the host tree. This page suggests how we can speed things up a bit.
They are rare trees in our valley, but the strangler figs that remain produce thousands of fruit, each one with hundreds of seeds. Possums love to eat these fruit and their dropping scattered under the tree are often made up of 90% fig seeds, nicely cleaned and ready for sowing.
Here, fig seedlings have been tied to hardwood stakes and their roots protected with elkhorn fern. Grown in they make a living screen for a west-facing 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 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.
When strangler figs are grown in a nursery, their long roots are vulnerable to drying out. However, if they are protected and surrounded by a humid atmosphere, aerial roots are sent downwards. The longer these grow, the higher up in a host tree the plant can be attached. As soon as the lower ends of the roots begin to access moisture and nutrients in the ground, the plant will grow rapidly. Once they attain this stage, strangler figs become 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. I find 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. By May 2013, fig roots were already starting to grow around the supporting tree. How will it look in 10 year's time?