Pterostylis is a genus of about 70 species of terrestrial orchids, most of which are Australian but the genus extends to New Zealand, New Caledonia and New Guinea.
Pterostylis grandiflora is one of the most attractive species because of its large, striped flowers in which the dorsal (or top) sepal and the petals combine to form a hood around the central column (the fused stamens, style and stigma). The leafy flower stem is a separate shoot to the rosette of radical leaves and may be up to 35 cm high. The 25-40 mm diameter flowers occur singly and are seen in late autumn and winter. The plants become dormant in summer when they die back to an underground tuber.
Although P.grandiflora is a little easier to grow than many other terrestrial orchids, it is cultivated mainly by orchid enthusiasts. Generally the plants are grown in pots in a freely draining, sandy mix. They require good air circulation in a protected position of about 50% sun during the growing period from late summer. During this growing period the plants must not be allowed to dry out. After the leaves have turned brown in late spring to early summer the pots are allowed to dry out completely. Repotting of tubers can be carried out in summer.
Propagation of orchids requires specialised methods and is rarely attempted by the casual grower. The following references provide further information on growing terrestrial orchids from seed.
- Australian Terrestrial Orchids from Seed; D K McIntyre, G J Veitch and J W Wrigley
- A New Medium for Raising Australian Terrestrial Orchids from Seed; G J Veitch and D K McIntyre
Both articles appear in Australian Plants, journal of the Australian Native Plants Society (Australia), March 1973.
Photo: Jill Dark