What does lithe lianas mean?

This is obviously a reference to the line in Dorothea Mackellar's poem about Australia, entitled "My Country". The section reads:

Green tangle of the brushes,

Where lithe lianas coil,

And orchids deck the tree-tops

And ferns the warm dark soil

This part of the stanza refers to the rainforests. Lianas are a type of rainforest vine, which coil upwards towards the sun through the thick tree canopy. "Lithe" means limber and flexible and so "lithe lianas" refers to the way these vines climb nimbly up the trees, curling around other plant parts.