Sturt's Desert Pea; a desert glory

I've been running an intermittent series on favourite trees for some time now, and was going to offer another today, but decided on a whim to instead introduce my favourite flower - so without further verbage, if you don't know it already, please meet....

.... Sturt's Desert Pea Swainsona formosa, growing here near Broken Hill, far western New South Wales.
This stunning sprawling creeper grows in desert country from the north-west coast
of Australia across to central New South Wales.

Driving through vast outback landscapes at 100kph, the glowing red and black flowers beam from the roadside and grab your attention from the periphery of your vision. They've been doing that for a long time, and surely since long before European settlement of the continent, but they're also associated with several prominent European explorers, beginning in 1699. That was when the remarkable pirate-cum-naturalist William Dampier in the Roebuck (provided by the British government) landed at what is now the Dampier Archipelago in the far north-west, having spent four days at Shark Bay. Here he described in his Voyage to New Holland, &c. (the title goes on for three paragraphs, as was standard) "a sort of creeping vine that runs along the ground.... and the blossom like a bean blossom, but much larger, and of a deep red colour, looking very beautiful". (I've dispensed with his randomly scattered capitals. For more on Dampier, I'd recommend Diana and Michael Preston's A Pirate of Exquisite Mind.)

In the same area (apparently King Bay) the great botanist-explorer Allan Cunningham also collected the plant again in March 1818, in his circumnavigational exploration with Philip Parker King in the Mermaid, though curiously his journal doesn't refer to it; I am relying on Ida Lee's excellent account.

However it is Charles Sturt with whom we always associate the plant, through its common name. It was he who brought it to public attention in his 1848 book Narrative of an Expedition into Central Australia, where he came upon it near the Darling River in western New South Wales. My understanding that he then between what is now Kinchega National Park and Broken Hill. "... we saw that beautiful flower the Clianthus formosa, in splendid blossom on the plains. It was growing amidst barrenness and decay, but its long runners were covered with flowers that gave a crimson tint to the ground." The first recorded use of the name Sturt's Pea that I can find is in the South Australian Register in March 1858, in a report of the Auburn Show.

Arid Lands Botanic Gardens, Port Augusta, South Australia.
The harshness of its habitat is pretty evident here!

Which brings us to the name, and this is not the only plant to have a vexed and tangled taxonomic history. I'm not entirely satisfied that I've fully understood it, but this is an attempt to summarise, without incorporating all the options used over the years. In 1832 the Don brothers George and David, Scottish botanists, rather cheekily coined the genus Donia for it, calling it Donia formosa; it's definitely Not Done to name something for yourself, but they claimed they were honouring their father. There seems to have been little furore, as the name disappeared just three years later when Allan Cunningham described it (presumably unaware of the Dons' work) as Clianthus dampieri. It was generally agreed that he was correct in including it in the New Zealand genus Clianthus, where it remained until 1990, but incorrect in not using Don's species name, formosus. (For a reason well beyond my ken, the species name is attributed to George alone.) Other names were used and discarded, until in 1990 Sydney botanist Joy Thompson asserted that it wasn't after all closely related to the New Zealand species and moved it to the largely Australian genus Swainsona. 

I have to say that it doesn't look like other Swainsona, but that is neither here nor there when it comes to relationships.

Swainsona galegifolia, near Merriwa, New South Wales.

In 1999 the great Western Australian botanist and iconoclast Alex George agreed that the desert pea is one of a kind and coined the lovely name Willdampia for it. Over in the east taxonomists were aghast - I heard one declaim that the name would be used "over her dead body". Fortunately it didn't come to that, and perhaps unfortunately George's creativity was consigned to history.

To be honest the flower doesn't initially even resemble a pea very much, so the question of whether it looks like a Swainsona is probably rather moot.

The flowers rise in clusters, several to a stalk, vertically from the spreading stems with grey furry
pinnate leaves. The most striking feature is the black-blue glossy 'boss' which grows from the standard,
the big single petal which looms over most pea flowers (see the previous photo).
In the desert pea though, the standard has effectively turned inside out, with the boss projecting forward.

Presumably this is to increase its visibility to pollinating birds. And here's another oddity... I can find not a single reference to anyone observing a bird visiting a wild Sturt's Desert Pea, though all agree it happens. The only pollinating reference I have is to New Holland Honeyeaters (which would not encounter the pea in the wild) visiting flowers in an open-sided greenhouse, where they received pollen on their bellies. A similar desert pea flower - in being red and growing at ground level - is the Upside Down Plant Leptosema chambersii. In the Great Sandy Desert in Western Australia recently I repeatedly found the flowering plants surrounded by bird footprints - honeyeaters and woodswallows were the most likely sources, but neither I nor any of my companions on the expedition ever saw the birds responsible. The tracks only appeared around this species in flower.

Upside Down Plants surrounded by numerous bird tracks, Great Sandy Desert.

Often Sturt's Desert Pea occurs in small patches, but after good rains it can spread across the sandy countryside, or cover rocky hillsides.

Roadside wildflowers in far northern South Australia in September 2016.

Although Sturt's Desert Pea grows naturally in every mainland state and territory except Victoria and the Australian Capital Territory, it was South Australia which in 1961 adopted the species as its official state floral emblem. 

As for me, it's always an exciting day when we come across this superb flower while driving or walking in the outback.

And if you come knocking on our door - and if you're in the area, please do so! - this is what will greet you.

NEXT POSTING THURSDAY.

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