Distinguishing sow thistle from other yellow-flowered plants involves observing key characteristics. The plant typically grows 30 cm to 2 meters tall, with hollow stems that exude milky sap when broken1. Its yellow flowers resemble dandelions but appear in clusters on branched stems, unlike dandelions which have single flowers per stalk1. The leaves are deeply lobed with a bluish-green hue, and the upper leaves clasp the stem2. Three species are common in Australia: Sonchus oleraceus (annual sowthistle), Sonchus asper (prickly sowthistle), and the native Sonchus hydrophilus, each with slight variations in leaf shape and prickliness1.

Classified as a weed in many regions, sow thistle can produce up to 25,000 seeds per plant with a 90% germination rate, making it highly invasive1. Its ability to thrive in various conditions, from tropical to arid environments, and in both agricultural and urban settings, contributes to its widespread distribution. The plant's adaptability and rapid growth can pose challenges for farmers and gardeners, as it competes with crops for resources and can harbor pests economically important to vegetable and fruit production, such as lettuce aphids and nematodes2.

Control methods for sow thistle include hand pulling, ensuring removal of as much root as possible to prevent regrowth. Regular mowing can help prevent seed production, though it must be done frequently due to the plant's long flowering period. For larger infestations, broadleaf herbicides may be effective when used according to local guidelines and safety instructions1. Letting the soil surface dry between irrigations can reduce establishment, while spring tillage significantly decreases sow thistle populations in agricultural settings2.

Despite its reputation as a weed, sow thistle offers several ecological and culinary benefits. The plant attracts pollinators like bees and provides food for various insects, contributing to local biodiversity1. Its deep roots can improve soil health by aerating compacted earth. Nutritionally, sow thistle leaves are rich in vitamin C, protein, and minerals, making them a valuable addition to salads or cooked dishes2. The young leaves are less bitter and better suited for raw consumption, while steaming can reduce the bitterness of older leaves2. Some cultures, including Greek and Māori, have long-standing traditions of incorporating sow thistle into their cuisine3.