Plants of
South Australia
Swainsona extrajacens
Fabaceae
Flood-plain Swainson-pwa
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Regional Species Conservation Assessments per IBRA subregion.
Least concern
Near threatened
Rare
Vulnerable
Endangered
Critically endangered
Extinct
Data deficient
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Botanical art

Kath Alcock paintings: 2

Etymology

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.

Distribution and status

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.
Herbarium regions: Lake Eyre, Eastern
NRM region: South Australian Arid Lands
AVH map: SA distribution map (external link)

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. Fruits are bladder or balloon-like pod to 20 mm long turning black or dark brown at maturity. Seeds are orange-yellow, semi-flat reniform seeds to 5mm long. Seed embryo type is bent.

Seed collection and propagation

Collect seeds between September and November. Collect mature pods, those turning brown and contain hard seeds. Mature pods can be found lying on the ground next to the plant. 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. From two collections, the seed viability were high, ranging from 90% to 100%. 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:
  Hide
LocationNo. of seeds
(weight grams)
Number
of plants
Date
collected
Collection number
Collection location
Date
stored
% ViabilityStorage
temperature
BGA 
MSB
14,800 (281.81 g)
14,800 (281.81 g)
100+26-Oct-2007MJT152
Lake Eyre
19-Sep-200890%-18°C
BGA 
MSB
21,900 (263.44 g)
15,500 (186.23 g)
100+26-Sep-2008DJD1123
Lake Eyre
20-Jul-2009100%-18°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.