Stemless thistle, white thistle, flat thistle

O. acaulon is nearly stemless, with the stalks rarely exceeding 10 cm in length. The short-stalked leaves are 15-38 cm long and deeply dissected into spine-toothed lobes and are narrow and oblong, grey or white-hairy on both surfaces. The flower heads are white or purple, and form at the centre of the basal rosettes of foliage. Seeds are grey-brown and about 4 mm long. They are four-sided, pitted and ridged lengthwise, with a pappus of cream-coloured barbed hairs about 25 mm long. In Australia, stemless thistles germinate from seed mainly in the autumn. Plants develop during winter into small rosettes, which grow rapidly in spring. They flower from October to November dying in summer. Some seeds germinate during winter and spring, but most of the resulting plants do not develop sufficiently to flower before dying. Under favourable conditions, some of these plants do survive and flower in the second summer. Reproduction is by seeds only.