Plants of
South Australia
Caladenia dilatata
Late Spider-orchid
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Regional Species Conservation Assessments per IBRA subregion.
Least concern
Near threatened
Critically endangered
Data deficient
Coober Pedy
Mount Gambier
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Botanical art

Kath Alcock paintings: 4

Prior names

Arachnorchis dilatata

Common names

Late Spider-orchid


Caladenia from the Greek 'callos' meaning beauty and 'aden' meaning a gland, referring to the colourful labellum and the glistening glands at the base of the column that adorn many of the species. Dilatata from the Latin 'dilatare' meaning widen, dilated or expanded, referring to the spreading segments of the sepals which have expanded glandular tips.

Distribution and status

Found in the South-east in South Australia, growing in heathlands and coastal scrublands, often in areas of high rainfall or in dry exposed environments in a variety of soil types. Also found in Victoria and Tasmania. Native. Very rare in South Australia. Common in the other States.
Herbarium region: South Eastern
AVH map: SA distribution map (external link)

Plant description

Annual terrestrial orchid growing from an underground tuber to 40 cm tall, with a single flower (rarely two). It has a single basal leaf to 6 cm long, oblong to elliptical or lanceolate and hairy. The flower is 20-80 mm mostly green with variable crimson median stripes on the sepals, the labellum is white with green lateral lobes, a maroon tip and calli. This is part of a complex of similar species but can be distinguished by its late flowering time, moderately large flowers and flattened clubs on both the petals and sepals. Flowering between October and November. Fruits are brown papery ellipsoid capsule. Seeds are very small brown ellipsoid seed with a long cylindrical translucent brown mesh-like covering.

Seed collection and propagation

Collect seeds between December and February. Collect fat capsules as they start to dry and turn brown. Pods will split and release the seeds quickly and will require monitoring. To increase the chances of collecting mature pods, it is recommended that a small breathable bag (ie. Organza bags) be used to enclose the developing capsules. Place the capsules in a container that will hold fine seeds and leave to dry for a few weeks or until the capsule split. Then carefully hold the capsule and tap it gently to release the seeds. Store the seeds with a desiccant such as dried silica beads or dry rice, in an air tight container in a cool and dry place, refrigerator or in liquid nitrogen. For the NVC South East Orchid Project two populations consisting of more than 200 individuals in total were recorded from the Geegeela and Big Heath Conservation Parks. Approximately 328,000 seeds (0.22 g) were banked from these populations. Seed viability ranged from 60% to 75%. Seed germination in Caladenia species is difficult without compatible mycorrhizal fungi.

Seeds stored:
LocationNo. of seeds
(weight grams)
of plants
Collection number
Collection location
% ViabilityStorage
BGA250,000 (0.171 g)10+12-Oct-2013KHB774
South Eastern
BGA70,000 (0.053 g)4 pods13-Jan-2014DJD2805
South Eastern
Location: BGA — the seeds are stored at the Adelaide Botanic Gardens, MSB — the seeds are stored at the Millennium Seed Bank, Kew, England.
Number of plants: This is the number of plants from which the seeds were collected.
Collection location: The Herbarium of South Australia's region name.
% Viability: Percentage of filled healthy seeds determined by a cut test or x-ray.