Seeds of South Australia
Tribulus astrocarpus (Zygophyllaceae)
Star-head (Walytjapiri)
List of species for Tribulus
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Seed collecting:
May to December
Herbarium regions:
North Western, Lake Eyre
NRM regions:
Alinytjara Wilurara, South Australian Arid Lands
IBRA regions
Kintore (GVD04)Great Victoria Desert
 Near Threatened
Breakaways (STP01)Stony Plains
 Near Threatened
Witjira (STP06) 
 Near Threatened   [edge of range]
Everard Block (CER03)Central Ranges
 Near Threatened
Pedirka (FIN04)Finke
 Least Concern
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 Tribulus]
Name derivation:
Tribulus from the Greek 'tribolos' meaning water-chestnut and translated into Latin as 'tribulos' which originally meant the caltrop, a 4-pointed military instrument, employed to lame advancing cavalry, and the name also applied to Tribulus terrestris. Astrocarpus from the Greek 'astron' meaning a star and 'karpos' meaning a fruit; alluding to the star-shaped fruit.
Found in the north and north-western parts of South Australia, growing on red sandy soil in river flats, drainage lines and flats. Also found Western Australia, Northern Territory and Queensland.
Native. Uncommon in South Australia. Common in the other states.
Plant description:
Prostrate hairy annual herb. Leaves alternate, with 3-6 pairs of leaflets, leaflets ovate-cuneate or oblong to 10 mm long. Flowers yellow to 8 mm diameter with 5 petals that slightly exceeding the calyx. Flowering between March and October.
Fruit type:
Woody star-shaped fruit to 25 mm across with 5 rigid horizontally spreading spines, splitting into 5 segments, each bearing 2 halves of the spines of 2 adjacent carpels.
Seed type:
2 seeds contain in the basal part of each woody fruit segment.
Embryo type:
Spatulate fully developed.
Seed collecting:
Collect fruits that are hard and brown. Some fruits maybe split and laying on the ground.
Seed cleaning:
No further cleaning is required if only fruits are collected. 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 one collection, the seed viability was high, at 90%.
Seed germination:
This species have physical and physiological dormancies that needs to be overcome for the seed to germinate.
Seeds stored:
LocationNo. of seeds
(weight grams)
of plants
Collection number
Collection location
% ViabilityStorage
1900 (65 g)
1900 (65 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.