Centaurea melitensis aka Maltese Star Thistle

Centaurea melitensis is an annual plant. It belongs to Asteraceae, the daisy family. Its names include Maltese star thistle and tocalote. Kew gives Macaronesia and the Mediterranean as its native range. This spans parts of southern Europe and North Africa. PFAF lists Portugal, Spain, France, Italy, and Greece. It also lists several Balkan countries. In Africa, it lists Morocco, Algeria, Tunisia, and northwest Libya. The RHS says it is not native to Britain or Ireland.

This plant grows to about 1.6 feet (0.5 metres) tall. As an annual, it lives its whole life within one year. PFAF says it blooms from July through September. Its seeds then ripen from September into October. Each flower has both male and female organs. Bees and flies help pollinate the flowers. Moths and butterflies do so too. The plant is also self-fertile: its own pollen can form seeds. These traits mean it needs no pollen from another plant.

In the wild, it grows on roadsides and disturbed ground. PFAF also lists garden beds as a place to grow it. Its species account says it needs a site without shade. It can grow in sand, loam, or clay. The soil must drain well. Soil with few nutrients can suit it too. The soil can range from mildly acid to mildly alkaline. It accepts dry or moist ground and can withstand drought. PFAF gives its USDA hardiness range as zones 6–9. Kew links the species to a subtropical climate.

PFAF describes how to grow this plant from seed in spring. One way starts with sowing in April in a cold frame. Move young plants into their own pots when large enough to handle. Then plant them in their final outdoor site in summer. You may also sow straight into the ground in spring. PFAF suggests trying autumn sowing, but gives no firm advice to do so. The same source warns that the plant may become a weed. Bear this in mind when choosing it for a garden bed.

PFAF lists no known edible uses and gives no food value. It notes past use as a remedy for kidney complaints. This does not show that the treatment works or is safe. The source lists no known hazards. That does not prove the plant is safe. It lists no other practical uses. The supplied evidence for this species gives no specific pest or disease details.