Bum-shaped leaves but rose-scented wood

What's rosewood when it's at home? By home I mean not French-polished in a sideboard but in, for example, Argentina, Bolivia, Brazil or Uruguay. That's where Tipuana tipu, just one of the world's rosewoods, lives and breathes.

And what a melodious botanical name. I gather both the genus and species name come from the local Peruvian name for the tree, tipa. A tipu is also a small bird or chicken.

So what is this tree, whether in its home in South America or planted in Melbourne Gardens (as photographed here in late December 2017)? Well it's a pea. Or if you like, a pea plant, or pea tree.

Look at these flowers and apart from a little frilliness they look like any other pea or bean flower. Also the leaves made up of small 'leaflets', typical of the rather large (with some 19,000 species) family Fabaceae.

There is only one species of Tipuana, commonly planted as a street tree in the tropics but doing very nicely in our temperate botanic garden here in Melbourne, Australia. It does even more nicely further north, where it has become an invasive weed in northern New South Wales and Queensland.

As noted in a fact sheet about its potential weediness, the tip of each leaflet the leaves in 'buttock-shaped'. In more polite circles we might describe this as emarginate (with a notch). Elsewhere, shaped like a bum.

There are quite a few trees and timbers with the common name Rosewood, most or all belonging to the pea family. The Convention of International Trade of Endangered Species of Flora and Fauna - better known as CITES - restricts trade in (rose)wood from all 300 species of the genus Dalbergia as well as what is called African Rosewood, Pterocarpus erinaceus. Unlisted is the New Guinea Rosewood, Pterocarpus indicus, found naturally from northern Australia through to Asia.

Then there are so-called Scentless Rosewoods, species of Synoum, in a different plant family, Meliaceae. That family is also where you'll find Dysoxylum fraserianum, the (Australian) Rosewood or Australian Rose Mahogany.  In fact Rosewood is a term used for a wide variety of tropical species, all of which share 'a dark red hue and high quality timber'.

Our Melbourne Gardens' Rosewood has one extra feature, a winged fruit. This is very unusual in the pea family and looks more like what you'd expect on a maple (Acer), although split in half.

So our rosewood, also called Pride of Bolivia, is variously masquerading as a Dalbergia, an Acer and, if you must, lots of tiny bums.

The images were taken in the Melbourne Gardens, late December and early January 2017, and the red flowered 'subshrub' in the last pictures is of course a Brachychiton