Journal Number 98
Caladenia alata at Rainbow Mountain - Dispelling a Myth
By Graeme Jane
Michael Pratt's photo of Caladenia alata prompted me to visit the area on 2 Nov 05 to seek it
out with some success. I noted several plants in flower, including one brilliant pink and several whites adjacent.
This started thoughts about why?
Then in the latest issue of the Journal the article by Eric Scanlen prompted further response, especially his surprise at records from south of the Bombay Hills (end of the earth??).
This he dismisses without further comment.
C. alata is by no means the only outlier present on Rainbow Mountain. Other "unexpected" plants found there are several kauri associates including the shrub: Corokia buddleioides, and the fern: Schizaea dichotoma. Also there from the Far North is the fern Dicranopteris linearis.
Then from the coastal areas there is warmth loving and very primitive land plant Psilotum nudum. Calochilus robertsonii is also seen there, but this is not so extraordinary as it seems, since it occurs also at several localities around Golden Bay and Nelson (but that is another story).
The explanation for these "anomalies" is quite simple. These are remnants from warmer climatic times when kauri and similar plants grew this far south.
There are in fact quite a number of species, especially ferns and their allies that occur in or near thermal areas around the Rotorua-Taupo area that only occur in the Far North. Rainbow Mountain perhaps hosts more of these species because it has some residual forest protected from recent volcanic eruptions and settler "improvements". These species can perhaps be regarded as refugees awaiting more favourable climatic changes in the surrounding landscape, maybe arriving in the next 1000 years or two.
Interestingly, the presence of Paracaleana minor - an Australian vagrant recorded from only one site near Rotorua over a very long period, probably has another more mundane explanation. It could have arrived during one of those periodic severe bushfire seasons in eastern Australia when smoke, ash and apparently orchid seed and insects are carried high into the atmosphere and brought eastwards in the jet stream in a few hours. More likely though (since it has occurred nowhere else), it arrived in soil on the shoes of a visitor to the thermal wonderland.