Journal Number 97
November 2005

AUSTRALIAN NOTES

Basalt Plains Greenhood Monitoring
By Dick Thomson
(From ANOS (Vic) Bulletin Vol 38:4 October 2005)

Out on the basalt plains where the wind blows and the sun rarely shines in winter; "Pleurisy Plains" as the locals know it, four Pterostylis species grow - one named and three to be named. They choose to grow more or less together, on the rocky basalt knolls where farmers have retained native grassland vegetation.

Our challenge today was to identify these orchids and indicate what proportion of the four species made up the approximately 4000 plants over about a dozen sites.

Prior to the day, and to help with identification, we had all undertaken detailed study of photographs of the leaves of each species, leaving us confused and with a belief that the task was impossible. After much discussion and peering at plants it was agreed that we could tell one species with about a 70% certainly and the others looked the same until they were in flower.

Our task was made a little easier when we found some of the Pterostylis sp. aff. mucida in flower. The consequence of the day's play was lots of plants marked for further monitoring as their flowers open.

You may ask why monitor now? Why not wait until they are in flower? A jolly good question!
This is partly answered by noting that when the grass and herbiage grows the plants are hidden. We cannot find them without a lot of difficulty and high risk of damage by trampling.

We also left with a further question. If the flowering periods of the four species overlap, might there also be hybrids present? And what of Pleurisy Plains? It was a beautiful, sunny day without a breath of breeze. Fantastic!