Journal Number 95
May 2005

ORIGINAL PAPERS

Stegostyla "minor"
By Mark Moorhouse

Dec 1982 saw me involved in a Forest Service scrub cutting contract on the south side of the Big Bush State Forest not too far from the Nelson Lakes National Park.

At the time it was a serious clash of interests. The indiscriminate cutting of virgin kanuka forests and my interest in our native orchids were at loggerheads. I decided to do an intensive survey of the plants on the blocks we were working on in the hope of presenting to the Forest Service hierarchy some evidence of the idiocy of their slash and burn policy.

Perfect orchid growing environment was being destroyed at an unprecedented rate in an attempt to beat the time frame set for the closing down of native forest cutting by Govt policy.

Amongst the 20 odd species I located were a couple of plants of the Caladenia family I had never encountered before and which I feebly attempted to explain away in Newsletter no. 6 in June 1983 as a possible hybrid between what was then Caladenia lyallii and C. catenata (now Stegostyla lyallii agg and C. chlorostyla).

To all intents and purposes to the uninitiated, it appeared like a giant C. chlorostyla. What I had failed to observe at that time was that the two rows of calli which ran down the centre of the labellum actually extended onto the central lobe and gradually diminished in size as they approached the tip.

So by definition these plants fitted the new category of Stegostyla (or did it? Read on!). What had taken my eye initially was their size (18-23mm across) and the unusual intense covering of red glandular hairs on the outer sides of all tepals.

This habitat was duly destroyed by the scrub cutting and although there were a couple of small reserves left intact, it became evident that there were none of this rare plant within these areas.

It was to be 21 years before another encounter (with hoots of jubilation!) of these same plants was made on my niece's property in the Baton Valley area, in Nelson's Western Ranges. Three plants were located in 2003 and two in 2004, thanks to my niece, Mrs Georgiana Upson's persistence. (I managed to mistime visits to the location 3 times in 2004).

Because of their scarcity, to date no specimens have been offered for study and no cross sections taken. Plants have been tagged for next year's studies. However, sketches and detailed digital photographs have provided some material which needs to be shared in the hope that other, more prolific colonies will come to light, and professional studies can proceed.

Plants are robust, up to 25cm in height with a typical Caladenia type of leaf, very linear to about 12 cm in length but quite narrow compared to Stegostyla lyallii and S. aff. alpina, being usually only 4mm or less wide.

The typical "tip burn" of the leaves of S. lyallii was not evident in this species.  Some stems of plants recently located have a reddish suffusion (others without) and are covered in white glandular hairs with a tiny red gland at the tip of each hair. The floral bracts were all situated around 15mm below the ovary which is approximately 20mm long, hairy with red vein markings.

Four of the five plants had two flowers. One, this year was pale pink, the rest white, but close inspection indicated that the pink one had no physical differences that we could see, other than colour. The flowers are fertile and some set seed.

The dorsal sepal stands almost erect in fully open flowers and the tip recurves. On fully open flowers the edges also recurve. The tip is quite acute and over-reaches the column and labellum wings. It is covered in red tipped glandular hairs.

In white flowers the outer dorsal surface is quite greenish similar to Caladenia chlorostyla. The dorsal sepal is relatively narrow for the Stegostyla family, being only as wide as the labellum wings, and this feature distinguishes it from both  S. lyallii agg and S. aff. alpina, both of which in the Nelson area, have dorsal sepals wider than the labellum wings.

The other sepals and petals are narrow ovate with quite acute flattish tips that often turn down slightly rather than forming the cupped tips of the other larger Stegostyla. These tepals are also covered in glandular hairs in similar fashion to the dorsal sepal but in addition have sparse glandular hairs at their inner base as well.

The column sweeps in an even curve and is weakly marked in erratic red bars and dots. The column wing is quite broad and almost evenly curved in the opposite direction to the column, reaching from top almost to the bottom of the column.

This feature seems to be a distinguishing point from the local S. lyallii which has a broad wing only at he top of the column and waists down to very narrow half way down the column.

The anther cap is bright green on top but reddish pink on the front below the connective, which is prominent, apiculate and down-turned. This feature is one distinguishing it from S. lyallii and may place it in Caladenia. (Taxonomy is only mooted pending further studies by those more qualified than the humble observer.)

The labellum carries two rows of laminar calli, but has strays outside this toward the front of the central area.It is weakly marked with red bars and blotches only a few of which extend up the side wings. The laminar calli are red stalked with yellow clubbed heads that lean forwards toward the tip.

The two rows of these calli extend onto the midlobe where they gradually shorten, losing the red coloured stems, and reducing to small yellow bumps by the time they reach the recurved tip of the midlobe.

The midlobe is fringed by long stalked calli which tend to stand straight and are a pale creamy yellow. These extend the full length of the midlobe but reduce in length towards the tip to raised bumps.

The labellum wings are tall, evenly curved to match the column, and the front edge may display some small undulations.

The plant has been tagged Stegostyla "minor" as it is about the size of the small two row S. lyallii species of Nelson environs. The habitat is similar to the other S. lyallii agg.

It seems to prefer mature kanuka with very little broadleaf shrub association. Elevation 400 to 600 meters at Nelson latitude. Like others of the family it grows where there is at least some exposure to sun for a part of each day.

Caladenia nothofageti, C. chlorostyla, Stegostyla aff. alpina, S. lyallii and S. lyallii agg. have all been found in this plant's location along with 40 odd other orchid species including what appears to be a variant form of Caladenia bartlettii.

Dear reader, please find inspiration to revisit your favourite montane kanuka haunts. There must be more of these plants out there somewhere. I am sure the Editor would be delighted to hear about new finds of what could easily be mistaken for S. lyallii.

Comparison with Caladenia aff chlorostyla (right)