Soliva pterosperma (bindii, jo-jo, onehunga) PP is a low, mat-forming annual with deeply divided leaves and inconspicuous heads where the stems branch. It flowers in spring and then each seed develops a short, sharp spine. A serious weed of lawns and roadsides between Perth and Albany. Native to South America.

Soliva pterosperma , GK

Sonchus (sowthistles) are annuals or short-lived perennials with erect, sparsely branched hollow stems producing latex when cut. The flower heads are composed of yellow ray florets, opening in the morning, closing in the afternoon. They can produce flowers all year round, but principally in spring and early summer. S. asper (prickly sowthistle) is a stout upright annual to 1.5m, with hollow stems and large, leathery leaves with very prickly margins. It is found on fertile, damp soils in disturbed areas from Geraldton to Esperance.

Sonchus asper , PH

S. oleraceus (sowthistle) is widespread on roadsides, gardens, market gardens and wasteland from Wittenoom to the Nullarbor. It is an annual or short-lived perennial, less robust than the previous species; the leaves are generally flaccid and are weakly prickly or have no prickles at all. Both are native to Eurasia and North Africa. S. tenerrimus (clammy sowthistle) is a scattered weed of islands and woodlands in the south-west of Western Australia. Similar in appearance to S. oleraceus, it can be distinguished by its deeply-lobed leaves with very narrow terminal segments. Native to the Mediterranean and south-west Asia. A native species, S. hydrophilus, is superficially similar to S. asper, but can be distinguished by its longer, undulate or shallowly-lobed leaves that are only slightly prickly.

S. oleraceus , RC

Taraxacum officinale (dandelion) is an occasional weed of lawns from Tom Price to Esperance. It is a perennial with a strong taproot and a rosette of toothed leaves. Unlike flatweeds, Hypochaeris species, the stems are hollow, with only ever one flowerhead per stem. The classic "dandelion" flowering heads can be produced throughout the year. They are up to 3cm across, contain yellow ray florets and are followed by a sphere of plumed parachute seeds. The plant exudes milky latex if cut. Native to Europe.

Taraxacum officinale , PH

Tolpis barbata (tolpis) is an annual with a basal rosette of leaves and spindly, widely-branched stems producing flowers in summer. The heads have ray florets only, sometimes all pale yellow or sometimes the outer florets are yellow and the inner ones brown. The bracts surrounding the heads are slender and curved downwards. Found in disturbed areas from Perth to Albany. Native to southern Europe.

Tolpis barbata , PH

Tragopogon porrifolius (salsify, oyster plant) is an erect annual or short-lived perennial to 1.3m, with a fleshy taproot sometimes cultivated as a vegetable. It has narrowly triangular leaves and solitary, lilac-coloured heads on swollen, hollow stalks. A garden escape, noted near settlements at Norseman, Albany and Bridgetown. Native to Europe and northern Africa.

Tragopogon porrifolius , GK

Tridax procumbens (tridax) is a low perennial, often rooting at the nodes. It has ovate, lobed, stiffly hairy leaves and solitary, erect flower heads. They are produced throughout the year and have cream ray florets and yellow disc florets. A native of central America, it is naturalised in disturbed areas around settlements in the Kimberley.

Tridax procumbens , GK

Urospermum picroides (false hawkbit) is an annual with slightly rough, hollow stems, a milky latex and irregularly toothed leaves. The distinctive urn-shaped, yellow heads are produced in spring. It grows on roadsides and other disturbed areas, often in moist situations, from Shark Bay through to Perth and inland to Perenjori. Native to the Mediterranean.

Urospermum picroides , PH