Plants of
South Australia
Caladenia tensa
Rigid Spider-orchid,
Inland Green-comb 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: 2

Prior names

Caladenia aff. dilatata R.Br., partly

Arachnorchis tensa

Common names

Rigid Spider-orchid

Inland Green-comb 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. Tensa from Latin meaning rigid or straight, referring to its straight, rigid lateral sepals.

Distribution and status

Found in the upper South-east in South Australia, growing in dry woodland and mallee on sandy loams. Also found in Victoria with four old record from the central west of New South Wales. Native. Uncommon in South Australia. Rare in Victoria. Presumed extinct in New South Wales. Endangered in Australia under the EPBC Act.
Herbarium regions: Murray, South Eastern
NRM regions: South Australian Murray-Darling Basin, South East
AVH map: SA distribution map (external link)

Plant description

Terrestrial orchid to 40 cm tall in flower with a single hairy leaf. Inflorescence on a slender hairy stem with one or two green flower with variable crimson striping, the large labellum is white with green lateral lobes, a maroon tip and small, sparse maroon calli. Most readily identified by the stiffly held sepals which are 45 mm long with short yellow clubs. Flowering between September and November. Fruits are brown papery ellipsoid capsule. Seeds are very small brown ellipsoid seed with a long 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 one population consisting of more than 40 individuals was recorded from the Mt Boothby Conservation Park. Approximately 38,000 seeds (0.02 g) were banked from this population. Seed viability for this collection was 61%. 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
BGA40,000 (0.019 g)6 pods3-Oct-2013DJD2764
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.