Sow Thistle is an erect, hairless, branched plant about 1000 mm tall with sprays of yellow, thistle type flowers at the ends of branches and large, soft, lobed leaves. Common Sowthistle is an erect, hairless, branched annual or biennial herb about 1 m tall with hollow stems which have a milky sap. The basal leaves are up to 30 cm long, form a rosette and are soft and lobed or toothed. The stem leaves are somewhat smaller and stem clasping. The yellow dandelion-like flower heads are clustered, each about 2 cm in diameter, with all the florets having a radiating petal-like blade.