Plants of
South Australia
Diuris sulphurea
Orchidaceae
Hornet Orchid
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Botanical art

Kath Alcock paintings: 7.

Etymology

Diuris from the Greek 'dis' meaning two and 'oura' meaning a tail, referring to the drooping lateral sepals resembling tails, on some species. Sulphurea from Greek meaning sulphur-coloured, referring to the colour of the flowers.

Distribution and status

Found in the lower South-east in South Australia, growing in damp sandy soils in open Eucalyptus baxteri forest and around swamp margins. Also found in Queensland, New South Wales, Victoria and Tasmania. Native. Rare in South Australia. Common in the other States.
Herbarium region: South Eastern
NRM region: South East
AVH map: SA distribution map (external link)

Plant description

Annual terrestrial orchid to 50 cm tall in flower. Leaves 1-3, linear, to 50 cm long, channelled, lax. Inflorescence on a slender stem with 1–7 bright-yellow flowers with prominent dark brown markings. Dorsal sepals obliquely erect, ovate, to 20 mm long, with a pair of large dark brown blotches near base. Lateral sepals deflexed, usually parallel, linear, to 25 mm long, green or green and brown. Petals erect or spreading to 26 mm long; claw short, brown; lamina ovate to elliptic, yellow. Labellum obliquely deflexed, yellow with transverse dark brown blotches near apex and other brown markings; to 15 mm long, 3-lobed with lateral lobes about half as long as mid-lobe; mid-lobe spade-shaped. Flowering between September and January. Fruits are brown papery ellipsoid capsule. Seeds are very small brown ellipsoid seed with an oval translucent brown mesh-like covering.

Seed collection and propagation

Collect seeds between December and March. 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 40 individuals in total were recorded from Binnim and Nangwarry areas. Approximately 89,000 seeds (0.04 g) were banked for these two observed populations. The seed viability was low for Nangwarry at 17%, the Binnum collection was higher however at 78%. Seed germination in Diuris species is difficult without the presence of compatible mycorrhizal fungi.

Seeds stored:
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LocationNo. of seeds
(weight grams)
Number
of plants
Date
collected
Collection number
Collection location
Date
stored
% ViabilityStorage
temperature
BGA30,000 (0.014 g)110-Dec-2013C. Dickson
South Eastern
1-Nov-201678%-80°C
BGA60,000 (0.027 g)211-Dec-2013DJD2776
South Eastern
1-Nov-201617%-80°C
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.