An uncommon plant today, I suppose; there's not a single image in Google's image search for this species!
Andy Hill, one of the garden's horticulturists, walked into my office as I was prepping this photograph for BPotD and exclaimed, “Oh, Zanthoxylum. That's fun to prune...not.” This climbing shrub gets my vote as the most “vicious-looking” plant in the Asian Garden, and from what I understand from Andy, doesn't just look vicious – it is vicious. To give an idea of scale, this section of the stem near the base of the shrub is about as thick as a baseball bat (a little below 7 cm in diameter).
Zanthoxylum is a member of the citrus family, the Rutaceae, so its relations include oranges, lemons and limes. However, instead of a hesperidium, the fruit of Zanthoxylum is a small, single-seeded capsule. I like to pinch these between the tips of my fingers and then enjoy the scent, which certainly has elements of citrus in it.
This particular plant was grown from seed collected by Keith Rushforth, plant explorer and author. Keith obtained the seed near the village of Chendebji in Bhutan at 2500m / 8200'. If you are interested in seeing the landscape of the area, perhaps the film “Travellers and Magicians” might appeal – I haven't seen the movie, but most of the villagers of Chendebji appear in it!
A few more photographs of it on the garden forums: Zanthoxylum oxyphyllum.
Science / conservation resource link: Mangroves, Fishponds, and the Quest for Sustainability, an essay by scientist Dr. Jurgenne H. Primavera of the Phillippines. “We scientists in developing countries need to come down from the Ivory Tower and disseminate results not only in peer-reviewed journals but also through advocacy and the popular media. We must not forget our hearts even as we apply our minds. We do science not in a vacuum but against the grinding poverty and environment-unfriendly character of modern times, and we can use our scientific knowledge to reduce suffering and make life more full for fellow humans and creatures.”. Discovered via Science Matters, an article by Dr. David Suzuki.