| Emex, Emex spinosa, Polygonaceae, Arctotheca calendula, Urochloa panicoides|
Emex australis, commonly known in English as Three corner jack, devil's thorn, or double gee (also doublegee, from the old Afrikaner name dubbeltge-doorn - 'devil's thorn'), is a herbaceous plant of the Polygonaceae. It occurs indigenously in South Africa and is also an invasive species in Australia & Texas in the USA.
Removal The most common and most effective method of removing the thorns from ones garden is by burning (find out about the relevant laws regarding burning of lawns in your area). There's also been tale of gluing carpet to a PVC pipe connected to the end of an extended paint roller, perhaps just a mohair roller.
Emex australis Wikipedia