Arachnorchis tentaculata – King Spider Orchid
A hairy leaf of the spider orchid
The king spider orchid is one of the largest orchids, and the most common spider orchid that grows in the Adelaide Hills. It can stand nearly a foot high, with the flowers nearly ten cm across. Generally, they have one flower per plant, but sometimes there can be up to three flowers on one stalk. This species is distinguished by having clubs on the end of its three sepals, as there are other orchids such as Arachnorchis stricta, which are very similar, but don’t have any clubs.
The orchid has a hairy bluish-green coloured leaf, with a slightly purple base. The leaf is generally fairly rigid and can be four to five cm long. On one occasion, I saw a leaf that was nearly 10cm high. The plant had put a lot of energy into the leaf, and would not flower that year.
These spider orchids are pollinated by a native wasp. The flower tricks the male wasp into believing it is a wasp, by giving of the scent of the female wasp, and through its deceptive (but beautiful) labellum or lip. Once the male wasp lands on the labellum, or the lip of the flower, it dislocates the pollen on to its head. After realizing that it has been tricked, it flies away from that flower with the pollen. After picking up the scent of another spider orchid, the same story happens again, and the second spider orchid is successfully pollinated. Sometimes the wasps can damage the labellum of the orchid, and this can be seen by it hanging lower than normal.
This is an albino form of Arachnorchis tentaculata. I have only seen this once, several years ago, even though I’ve returned to that site more recently. This is a rare form.
Several growers in Adelaide have been able to successfully grow these orchids. One grower told me that the young seedlings tend to require an adult plant to be present, for survival. This helps ensure that there is fungi there. From seed, the spider orchids take about five years to mature and be able to flower. The plant can live for up to nine years, and should put up a leaf each year, but it may not flower each year.
Personally, this is one of the more delightful orchids, as it has pretty colouring, and is one of the larger orchids.