Orchid Season

brown-veined shell orchid

Over 300 species and subspecies of terrestrial orchids (of the family Orchidaceae) are found in the south-west of Western Australia, the largest number of terrestrial orchids in Australia [1]. My friends at Nuts about Natives have 18 species of orchids growing in the bush on their property (another species hasn’t yet flowered, but when it does it will be the 19th). I was lucky enough to see four of the early flowering ones in all their glory at the beginning of July.

The terrestrial orchids (of which Australia has many species) form mycorrhizas and need fungal partners in order for seedlings to survive beyond the germination stage. In at least some species the orchid needs the fungus throughout the orchid’s life. In these associations the orchid gets the better deal and in effect harvests the fungus. [2]

Terrestrial orchids have a symbiotic relationship between the underground mycelium of mycorrhizal fungi and the orchid’s roots [1]. The mycorrhiza* is not parasitizing the plant, the association is commonly mutually beneficial, but often the orchid is getting the better deal [2]. Orchid seeds are so tiny that they don’t contain all the nutrients necessary for their development, so they conscript mycorrhizae to provide starches for the plant [1].

brown-veined shell orchid

Pterostylis aspera (Brown-veined shell orchid, above) was found flowering for the first time this year, with a colony of three plants. One of the plants has been protected with a wire enclosure (the rabbits will massacre anything) to ensure its return next season.

short-eared snail orchid buds

Pterostylis brevisepala (Short-eared snail orchid) had not yet opened. Maybe next time I visit I will get to see it.

inside a helmet orchid

A colony of Corybas recurvus (Helmet orchids) grows under some dead and rotting woolly bushes (Adenanthos cygnorum). The location meant I had to crawl in under the branches and it was hard to get a good shot. I’m just glad it hadn’t rained for a few days and the ground wasn’t squelchy. My friends were going to burn this area because the woolly bushes were old and dying and needed a fire to provide space for the next generation of seeds to germinate. Despite some orchids germinating after fire, C. recurvus is killed by fire. Luckily, before the burning happened, the orchids were found and their home among the rotting woolly bushes was saved. A favoured habitat of this orchid is on leaf litter and rotting wood [1], which is why it popped up here.

Corybas recurvus is widely distributed throughout the lower south-west of WA from just north of Bunbury to the east of Albany, with a disjunct occurrence near Gingin. [1]

helmet orchids growing on rotting wood and leaf litter

Florabase agrees with Hoffman and Brown’s distribution, and Ben from Nuts about Natives said this population is slightly outside the published known distribution, but only just.

As they are known to occur both north (Gingin) and south (Bunbury and beyond) of us I think it is very likely there will be populations in between in suitable habitat and our population is perhaps just one of many. Excessive clearing and disturbance (eg. from grazing) between Bunbury and Gingin (i.e. metro Perth) especially around their preferred habitat along rivers, etc. probably accounts for why they may not have been reported, not to mention that they could easily be overlooked. I expect that other populations nearer to Perth are now known tucked away on private property or the like.

coastal banded greenhood

A couple of months ago when I visited in May, some Pterostylis vittata (Banded Greenhood) had buds that weren’t quite open. I was annoyed that I would miss them, but another patch waited to flower when I was visiting this time, so I was happy. These plants were tentatively identified by an orchid expert as P. vittata, but the characteristics were not clear. The plants have brown rather than green bands, so they could be the Coastal Banded Greenhood (Pterostylis aff. sanguinea), which hasn’t yet been scientifically identified [1]. (There are many native orchids which haven’t yet been scientifically named.)

=^.^=

*Mycorrhizal fungi are what cause fairy rings around trees. The biology class when fairy rings were mentioned was my favourite. Maybe if they had talked about magic more often I would have stuck with it :)

You demi-puppets that
By moonshine do the green sour ringlets make,
Whereof the ewe not bites, and you whose pastime
Is to make midnight mushrooms.

said Prospero in The Tempest (act V, scene I)

References

  1. Hoffman & Brown (1998) Orchids of south-west Australia (rev 2nd ed) Nedlands, WA: UWA Press.
  2. Lepp, Heino (2008) Mycorrhizas. Canberra: Australian National Botanic Gardens.

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