Journal Number 109
August 2008

ORIGINAL PAPERS

Pterostylis Oddities
By Gordon Sylvester

On a recent foray into Arthurs Pass National Park at Kelly's Stream, it was noted the confusion that the genus Pterostylis appears to display.

At one end of the Cockayne Nature walk Pterostylis oliverii is very prevalent, while at the other end of the same track less than a kilometre away there is a "confusion of species". All show elements possibly of P. irsoniana, P. australis, and P. oliverii. The early flowers display an affinity to P. cardiostigma, which is not present in the area - or I should say has not been identified in the area. Another trait seen is the twisted labellum of P. montana agg.

Both ends of the track in question are about the same height above sea level - about 360m. rising to about 380m in the middle of the track. There have not been any Pterostylis species noted in this elevated area of the track. Hopefully there will be further investigation next spring.

It is interesting to note some comments in the Proceedings of the Royal Society 1935; 64: 1-10 where RM Laing and HW Gourlay recorded the confusion of Pterostylis species in the Bealey river basin, later recording that "None of these species is typical of their representatives elsewhere. They occur in a great variety of forms impossible to classify satisfactorily. Intermediates between P. oliverii, P. banksii and P. graminea are all to be found".

It appears that nothing has been done since 1962. The only other record I have of any visits to the area are all by members of our Group. Bruce Irwin 1949, Brian Molloy 1998, and Eric Scanlen 2004 passed through on his South Island Odyssey.

What do we know? Historically...

Leonard Cockayne had a bach (crib) in the Kelly's Stream area and spent time there. The nature walk is named after him. It is not known if he carried out any investigations in this area.

RM Laing and WRB Oliver explored the Upper Bealey in 1929 and noted P. areolata, P. oliverii, RM Laing and HW Gourlay explored the Bealey River in 1935 and noted Pterostylis banksii, P. australis, and P. graminea. CJ Burrows explored the Waimakariri Basin in 1962 and noted in addition to Laing's records P. irsoniana, P. mutica (tristis), P. venosa, P. cycnocephala (tanypoda).

There are no public records of any other visits. Conversations with DoC staff at the Arthurs Pass field and visitor center indicate little or no knowledge of any of the orchid populations.

There is a lot of variation in floral characteristics, including leaves and method of display.
P. oliveri and its intermediates display both erect and recumbent habit. Some flowers display the twisted labellum of montana and the rolled labellum of irsoniana. The galea is just as confused showing the australis trait, the montana trait as well as the banksii trait.

Leaves run the range of shapes from montana to graminea to oliveri: anywhere between 3 to 6 leaves overtopping or not dependent on the parentage.

A visit to the Taipo River, a tributary of the Taramakau River some three years ago revealed what I thought was an immature P. cardiostigma, because of its coloration and the habit of the sepals in the immature bud. When I went back to look at the plant it had been disturbed and uprooted on the roadside. I had put a query around the identification due to the location in deep forest on a damp road side and the month (October). I have not noted any other specimens in this location since. Reason suggests they are still present. Having seen the Kelly's stream site, I am convinced this is so.

The questions now include, what are the strange Pterostylis species I had noted from the Mid Taramakau River flats, Callagans Water Race Track, Sandstone Road, Mahinapuna Forest, trackside Franz Josef Track as well as other sites intimated to me by others. All of them with a common trait; damp ground.

This leaves the question of whether the plants are naturally fertile or are extended by daughter bulbs.

1. What are the chromosome counts?
2. Are they primary or secondary hybrids?
3. What is the area of distribution of the plants?
4. Is there consistency in the population?
5. What is the primary stock and its distribution?