Tribulus is native to Kure and is abundant in open areas. Its leaf pattern and yellow flowers are unmistakable. Tribulus produces sharp thorny seeds that will get your attention. There is some die-back of Tribulus in winter, but otherwise, it is perennial.
Tribulus cotyledons are large and blunt-ended, giving them an almost rectangular shape, and have an obvious central nerve. The seeds are large so if in doubt you can always dig one up, though dig with care lest you get a thorn in the finger!
The true leaves grow out one at a time and are immediately recognizable by the many-branched leaf pattern (technically paripinnate, a word that doesn’t even occur in my dictionary of biology). Tribulus grows as a trailing vine with weak nodes, so if you try to pull up one vine it will generally separate from the rest of the plant.
Description: Prostrate trailing subshrub, branches subascending; leaves paripinnate, leaflets about 8 pairs, oblong; silky-pubescent, about 1 cm long; stipules falcate acuminate; flowers solitary, yellow, sepals 5, silky; petals 5, obovate; stamens 10, on base of annular 10-lobed disc, 5 longer ones opposite the petals, 5 shorter ones each with a dorsal gland; ovary sessile, hirsute, style short, stigmas 5; fruit of horned woody cocci, tuberculate, pubescent, partitioned within, compartments 1-seeded (Stone, 1970; p. 349).