Caladenia – Spider orchid

Distribution:
Over 100 species, most of which are endemic to Australia. Some species are found in New Zealand, and one species is found in Indonesia, Malaysia, and New Caledonia.

Plant Description:
Flower spikes 5 to 90 cm tall, with only one leaf. Often the petals are very long, giving the flower the shape of a long-legged spider. Caladenia has an attractive glandular, movable labellum with a decorative callus. Many species are sex-deceptive flowers and are pollinated by male thynnoid wasps (spider orchids). The other species are nutrient-deceptive flowers (fairy orchids).

Caladenia_HarlequinXflava — Caladenia Harlequin x flava

Cultivation:
Spider orchids are a challenging plant for terrestrial orchid cultivation and are not recommended for inexperienced enthusiasts. Since they have very few roots, they rely entirely on mycorrhizal fungi for water and nutrient uptake. These fungi are found at the base of the stem, between the leaf and the tuber. However, some species and hybrids are somewhat easier to care for. All plants exhibit a summer dormancy and survive as small tubers, protected by a tough fibrous tissue. The single leaf appears in early or late autumn, and the plants flower in late winter, spring, or early summer. Cultivate in a sunny or partially shaded location.

Hardy down to -2°C. Regular watering during the growing season is essential. Reduce watering once flowers appear, and stop completely once the plants go dormant. Keep potted plants completely dry during their dormant period. However, small plants and seedlings should receive occasional watering during the summer to prevent them from drying out. In late summer, the plants should be temporarily moved outdoors. Cool nights and some rain will end their summer dormancy and stimulate new growth.

Caladenia_macrostylis — Caladenia macrostylis

Recommended soil mixtures:
80 to 90% mineral, depending on availability. Volcanic granules, volcanic stratification, pumice, Seramis, 10 to 20% acidic organic components. Rhodohum has proven effective. The potting soil must be well-draining, with a pH of 5 to 6. An organic substrate consisting of 90% Rhodohum with 10% mineral components also yields good results. The mycorrhizal fungi of Caladenia grow primarily in the topsoil. Therefore, a top layer of wood fibers or pine needles promotes growth. For mineral substrates, fertilize with slow-release fertilizer. Approximately 0.5g of Klanz autumn fertilizer per plant at the bottom of the pot. See also potting soil.

Caladenia_HarlequinXapplanata — Caladenia Harlequin x applanata

Caladenia_longicauda — Caladenia longicauda

Recommended reading:
Cultivation of Australian native orchids produced by the Australasian Native Orchid Society, Victorian group Inc. Helen Richards, Rick Wootton, Rick Datodi.
Orchids of Western Australia produced by the Western Australian Native Orchid Study and Conservation Group. Kingsley W. Dixon, Bevan J Buirchell, Margret T. Collins
Native orchids of Australia. David Jones, 1993. Reed, ISBN 0 7301 0189 4.
Orchids of south-west Australia. Noel Hoffmann and Andrew Brown, 1992. University of Western Australia Press, ISBN 1 875560 13 0.
The Orchids of Victoria. Gary Backhouse and Jeffrey Jeanes, 1996. Melbourne University Press, Carlton, Victoria. ISBN 584.1509945.
Field Guide to the Orchids of New South Wales and Victoria. Tony Bishop, 2000. Second edition. University of New South Wales Press. ISBN 0 86840 706 2.