Soliva sessilis (Onehunga weed)

Kingdom: Plantae
Clade: Angiosperms
Clade: Eudicots
Clade: Asterids
Order: Asterales
Family: Asteraceae
Genus: Soliva
Species: S. sessilis
Binomial name: Soliva sessilis
Synonyms: Soliva daucifolia, Soliva pterosperma
Common names: Onehunga-weed, Burrweed, Lawn burrweed, Lawnweed, Common soliva. It is one of several plants known as Field burrweed, Bindi weed, Bindii, or Bindi-eye.

Soliva sessilis is a low-growing, herbaceous, annual weed known for its tiny sharp-needled seeds. Originally native to South America, the plant is now well established in many places around the world, including New Zealand where it is an invasive species in lawns and turf areas.

The seeds germinate in the bare patches of a lawn or turf in the autumn. Over the winter it grows into a small flat rosette with many-branched stems. The branched stems may root at the nodes and form additional rosettes. The plant has small, and finely divided feathery leaves reminiscent of yarrow. Soliva sessilis has a shallow fibrous root system rather than creeping rhizomes. In the late spring and early summer small bright flowers appear and if the plant is allowed to develop it produces a number of upward-pointing rosettes of seed pods nestled at the branch junctions, right at ground level. As summer intensifies the plant dies off and these fruits harden, usually with their spines pointed right into the air. These are the spined fruits that can't be walked on when one is barefooted. They will also penetrate the pads of dogs and cats. Because this plant is very small in size it usually passes beneath the mower blades without being touched each time the lawn is mowed.

Having Soliva sessilis can be a sign of sour soil with a low pH.
Soliva sessilis can be manually removed by pulling it out at the roots, usually when it's grown big, and started to flower, and before seeding - especially after rain when the ground is softer.

Thanks to Wikipedia for text and information: https://creativecommons.org/licenses/by-sa/3.0