Centaurea benedicta aka Blessed Thistle

Centaurea benedicta is an annual in the daisy family, Asteraceae. Many references list it under its synonym, Cnicus benedictus. Its common names include blessed thistle and St Benedict's thistle. Kew gives its native range as Europe east to Xinjiang. It grows in temperate regions and is not native to Britain or Ireland. Wild plants occupy dry, sunny sites, including stony ground and fields.

Plants reach about 2 feet [0.6 metres] in height. Their annual life cycle suits beds renewed from seed each year. Flowers appear from May to September. Seeds then ripen between July and October. Each flower has both male and female organs. Insects pollinate the flowers. The plant has ornamental value as well as a long history of use. European growers have raised it for herbal use and seed oil.

Choose a sunny site with soil that drains well. The plant cannot grow in shade. It accepts sandy soil, loam, and clay where drainage suits it. Soil may be mildly acid, neutral, or mildly alkaline. It prefers dry conditions but also grows in moist soil. Ordinary garden soil supports growth, while well-manured soil gives better results. Plants For A Future lists USDA zones 7–10. Sow seed where plants will grow in spring or early autumn. At 50°F [10°C], germination takes about two to six weeks. The same source flags some weed potential.

Several parts have recorded food uses. Young leaves can be eaten raw. Unopened flower heads have served as a substitute for artichokes. Their small size makes this use awkward. Boiled roots have been used as a cooked green. The herb also serves as a flavouring, though the part is unspecified. Seeds yield oil that people have used when other oils were scarce. Historical herbal practice used the plant for many ailments. It still appears in herbal tonics, but this does not establish medical benefit.

Food use does not mean the plant is free of hazards. It may trigger allergies in people sensitive to the daisy family. Contact may also irritate the eyes. Strong preparations can irritate the stomach and cause vomiting. Increased stomach acid may worsen ulcers or heartburn. Possible effects on bleeding warrant caution with blood-thinning medicines.