THE GENUS Drakaea and MISS DRAKE by Brian Milligan

Drakaea is a genus of terrestrial orchids found only in southwestern Western Australia. Commonly called Hammer Orchids, each of the nine species in the genus has a single, ovate or heart-shaped leaf, and a single flower carried on a tall, wiry stem. Hammer orchids grow in sandy soil, and flower during spring. The most conspicuous features of the flower are the prominent column bearing the sexual organs, and a warty labellum attached by a hinged strap. Whereas the column and labellum are held above the flower, the narrow, rather insignificant petals and sepals dangle downwards.

Although hammer orchids are difficult to find in the wild, they are well documented in the orchid literature because of their unusual method of reproduction. The flowers are pollinated by male thynnine wasps, each of the nine Drakaea species being pollinated by a different species of wasp – this specificity avoids contamination of the gene pool by hybrids.

Like most wasps, male thynnine wasps have wings but the females are wingless and spend much of their lives in burrows. Only when sexually mature does the female thynnine wasp emerge from her burrow to climb a nearby grass stalk. She then releases a pheromone (sex attractant) that lures male wasps, often from a considerable distance downwind. Firmly grasping her body in his legs, the male takes the female wasp on a nuptial flight before returning her to the burrow (or possibly dropping her from a great height after he has had his wicked way!).

Returning to the hammer orchids …. The labellum of a hammer orchid also emits the same (or a very similar) cocktail of odours as the female thynnine wasp. Thus the male wasp is attracted to the flower’s labellum, (which by no coincidence has a similar shape to that of the female wasp), grasps it firmly, and then attempts to embark on his ‘joy flight’. Because the labellum is firmly attached to the flower, all that happens is that the ‘hinge’ swings shut, causing the wasp to plummet headfirst onto the column. In the process his head or back is liberally smeared with pollen.

Learning nothing from the experience, the male wasp picks himself up and heads off in search of another ‘mate’. Finding another flower, he repeats the exercise, this time transferring the pollen from his head to the stigma on the column. Thus the flower is pollinated, and eventually a seedpod develops.

The genus Drakaea was named by the famous British botanist John Lindley in 1839. He named it after Miss Sarah Anne Drake, the botanical artist who drew, painted, and made lithographs of many of the orchids and other plants that Lindley described. She lived with the Lindley family (who called her ‘Ducky’) between 1830 and 1847, and retired to Norfolk only after Lindley’s Botanical Register ceased publication in 1847.