Seeds of South Australia
Tribulus terrestris (Zygophyllaceae)
Caltrop
List of species for Tribulus
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Seed collecting:
April to January
Herbarium regions:
North Western, Lake Eyre, Gairdner-Torrens, Flinders Ranges, Eastern, Eyre Peninsula, Northern Lofty, Murray, Southern Lofty, South Eastern
NRM regions:
Adelaide and Mount Lofty Ranges, Alinytjara Wilurara, Eyre Peninsula, Northern and Yorke, South Australian Arid Lands, South Australian Murray-Darling Basin, South East
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. Terrestris from the Latin 'terra' meaning earth and 'astris' meaning -ish; possibly referring to the species prostrate habit.
Distribution:
An introduced species native to Old World tropical and subtropical regions in Asia, Africa, Mediterranean Europe and northern Australia and recorded across South Australia, growing in disturbed sites and waste land. Introduced to Western Australia, New South Wales and Victoria. Considered native in Queensland. Status uncertain in the Northern Territory.
Status:
Introduced. Common in South Australia. Common in the other states.
Plant description:
Prostrate hairy annual herb. Leaves opposite, unequal, with 4-7 pairs of leaflets, leaflets obliquely oblong to 10 mm long. Flowers yellow to 15 mm diameter with 5 petals to 6 mm long and sepals to 3 mm long. Flowering between February and July.
Fruit type:
Woody fruit to 10 mm long, glabrous or lightly hairy, with 2 divergent spines to 8 mm long in the upper part and 2 shorter spines near the base pointing downwards and breaking into 5 segments. 
Seed type:
2-4 seeds in each woody segment.
Embryo type:
Spatulate fully developed.
Seed collecting:
Collect fruits that are hard and turning brown. Some fruits maybe split and laying on the ground. Be careful when collecting as fruits are spiny.
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 germination:
This species has physical dormancies that needs to be overcome for the seed to germinate.