Ficus microcarpa (syn. Ficus retusa)
The Ficus microcarpa (syn. Ficus retusa) or Chinese Banyan is perhaps one of the biggest exports of Chinese bonsai after the Chinese Elm. While native to China and most of Topical Asia, it has naturalised in many parts of the world, where it is often regarded as an invasive species as it is saprophytic and a very tenacious species. The microcarpa has medium to dark green alternate oblanceolate leaves, about 5-6 cm. Its trunk is heavily butteresed, and it has a smooth, light-grey to reddish-brown bark with brown pronounced horizontal lenticels.
Styles: As bonsai, the large leaves do reduce considerably, but they can still be between 5-10 cm long, and as such the Moreton Bay Fig is best suited to medium or large bonsai. They are usually grown as upright style bonsai.
Position: In tropical regions, it is grown outdoors and requires a full sun aspect. In temperate parts of the world, it is grown indoors as it does not like temperatures below 6°C. In colder climates, it needs a heated conservatory or greenhouse where day temperatures are maintained at over 15°C temperature and night temperatures above 6°C.
Watering: Ficus like moist soil but hate a waterlogged soil. Water in the morning when it is needed the most and the bonsai will use the surplus water before the night.
Feeding: Use a low potency balanced organic feed. Using inorganic high potent fertilisers may increase growth rates, but it will also lead to larger leaves and coarser branching.
Repotting: These fast-growing trees love to be repotted every year. It is best to ensure that nighttime temperatures are well above 10°C to ensure a stress-free repotting. The Ficus can deal with a variety of methods of root pruning but to be on the safe side, do not bare root and do not reduce the root ball by more than a fifth especially if growing them as indoor bonsai in colder parts of the world. Use a rich well-draining soil, one part well-mulched bark, one part pumice, and 1 part Akadama will provide a right mix of air, water and nutrients.
Pruning: This is a continuously growing species so need to be frequently pruned. Let the growth extend to about 6 or 7 nodes and then pruning back to leave 3 active notes. The Moreton Bay Fig respond well to pruning and ramifies, slowly starting with somewhat coarse branching, but does eventually form a fair level of branching.
Wiring: While the Ficus branches can be wired at any time of the year, remember they are continuously growing species so will need constant vigilance to ensure that the bonsai wire does not scar the branches.