Wednesday 25 January 2012

Blue quandong: tree of many colours


Not that you would know from the way I've been avoiding the subject, but the blue quandongs (Elaeocarpus angustifolia, syn. E. grandis) are flowering at the moment.

1 January 2012


24 January 2012


25 January 2012


They are magnificent trees, although not really suitable for small gardens. Not only do they grow rapidly, but they also spread out. Mature trees are buttressed (I'm sure we can all identify with that) and have extensive crowns. They also do this.

Still, if you've got the space, they are stunning to look at. Leaves are light green, turning scarlet before they fall. As with most vine forest trees, leaves drop throughout the year, so there is always a decorative highlight or two.

1 January 2012


The fruit has pale green flesh enclosed in an iridescent blue skin. Botanist David Lee uncovered the source of the blue colour — it is not a pigment, as is the case with many other fruit, but a property of the microscopic structure of the skin. It is produced by multi-layer interference in a similar way to the iridescent blue of bird feathers and butterfly wings. [Some of the links are dead in that post. I will have to write an updated version.]

In Nature's Palette, Lee writes:
This tree is sacred in India, where the stony inner fruit is highly ornamented and used for bracelets and necklaces (malas) for reciting prayers and sacred sounds. The sadhus (spiritual seekers) wandering the countryside frequently carry malas of rudraksha [local name for the tree] beads...I discovered that the interference color of the rudraksha fruits is indeed produced by a structure whose cellulose layers are of the predicted thickness to produce blue. This structure, which I have called an "iridosome", is different from those seen in leaves; it is secreted by the epidermal cells of the fruit and is located outside the cell membrane but inside the cell wall.

20 November 2011


Despite their attractive appearance, the fruit are not much favoured by the pademelons. They take a bite and then move on, so forest floor is littered with barely nibbled ripe quandongs. Wompoo and topknot pigeons, spotted catbirds and tooth-billed bowerbirds, on the other hand, make the most of the all you can eat buffet.

20 November 2011

The seeds are enclosed in a wrinkled endocarp that looks a bit like a brain after a night without sleep because of an owl. They are also plentiful on the forest floor. (Better pictures here.) It's a wonder that everything isn't coming up quandongs.

25 January 2012

Reference
Lee, D. (2007). Nature's Palette: The Science of Plant Color. University of Chicago Press.