Annual buttonweed

Cotula australis, the annual buttonweed or southern water-buttons, is a small annual herb of the daisy family (Asteraceae) native to Australia and New Zealand and widely naturalised on disturbed ground in temperate regions worldwide. It grows close to the ground in a thin, prostrate mat, sending up a few slightly erect, spindly flowering stems from a slender taproot. The soft, finely divided leaves are bipinnatifid into narrow, fringe-like lobes and have a faintly aromatic scent when crushed. The flower heads are tiny button-like discs only a few millimetres across, borne singly on slender peduncles; they consist of minute yellow disc florets surrounded by greenish-brown bracts, with the ray florets reduced to fertile pistils that lack petals and stamens. The fruit is a flattened, narrowly winged achene about a millimetre wide. The species occurs on lawns, paths, gardens, footpaths and other open, frequently trodden habitats.