Seeds of South Australia
Swainsona extrajacens (Leguminosae)
Flood-plain Swainson-pwa
List of species for Swainsona
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Seed collecting:
September to November
Herbarium regions:
Lake Eyre, Eastern
NRM region:
South Australian Arid Lands
IBRA regions
Strzelecki Desert (SSD05)Simpson Strzelecki Dunefields
 Rare   (IUCN: RA d(ii))
Murnpeowie (STP03)Stony Plains
 Rare   (IUCN: RA d(ii))
Coongie (CHC06)Channel Country
 Rare   (IUCN: RA d(i,ii))
Lake Pure (CHC07) 
 Rare   (IUCN: RA d(i,ii))
RSCA map:
Regional Species Conservation Assessments per IBRA subregion. Please click the thumbnail map.
AVH map:
Australian distribution map (external link)
SA Census:
Census of South Australian plants (external link)     [genus Swainsona]
Name derivation:
Swainsona named after Isaac Swainson (1746-1812), an English scientist and horticulturalist who had a private botanic garden near London. Extrajacens refers to the remote location of the populated areas.
Found in the northern-east corner of South Australia, growing on clay-loam floodplain . Also found in New South Wales. 
Native. Rare in South Australia. Rare in New South Wales.
Plant description:
Erect annual herb to 30cm high with several stems arising from a taproot. Leaves ovate to ovate-elliptic, to 35 cm long with 9-25 leaflets, hairs on the margins on the upper surface, apex recurved with a short point. Inflorescence a spike to 15 cm long with 5-10 purple pea flowers. Flowering in spring and summer.
Fruit type:
Bladder or balloon-like pod to 20 mm long turning black or dark brown at maturity.
Seed type:
Orange-yellow, semi-flat reniform seeds to 5mm long.
Embryo type:
Seed collecting:
Collect mature pods, those turning brown and contain hard seeds. Mature pods can be found lying on the ground next to the plant.
Seed cleaning:
Place the pods in a tray and leave to dry for a week. When dried the pods can become hard and difficult to open. Use a rubber bung to rub the pods or break the pods open with your fingers to dislodge the seeds. Use a sieve to separate the unwanted material. 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.
Seed viability:
From two collections, the seed viability were high, ranging from 90% to 100%.
Seed germination:
This species has physical dormancy that need to be overcome for the seed to germinate (e.g. nicking or softening the seed coat).
Seeds stored:
LocationNo. of seeds
(weight grams)
of plants
Collection number
Collection location
% ViabilityStorage
14800 (281.81 g)
14800 (281.81 g)
Lake Eyre
21900 (263.4 g)
15500 (186.23 g)
Lake Eyre
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.