This is a very unusually combination created from something very common.
This plant is very common in Hong Kong. It's a herbal plant that cures certain skin irratation with external application.
We see this plan almost everywhere in Hong Kong - a lot taller and bigger than this Pen Jing BUT the trunk not as thick. Perhaps it shows the time it took to shape this Pen Jing.
Also this is also the first time I see this plant used in Pen Jing.