- HPRWA SCORE 17
- FAMILY Asteraceae
- CATEGORY Grasses & Groundcovers
milk thistle, Mary's thistle (Silybum marianum)
Milk thistle is a spiny medicinal herb capable of forming dense, impenetrable thickets in pastures and grasslands.
- A stout herb with glabrous to slightly pubescent stems of 20-250 cm (7-100 inches) height
- With spiny-dentate leaves
- Stem leaves are sessile, smaller and less deeply divided, with yellowish white spines up to 8 mm (0.3 inch) long
- A native of the Mediterranean region that has been used medicinally for at least 2000 years
- Reproduces by wind-dispersed seeds
- A priority pest controlled by the Maui Invasive Species Committee
- Produces copious amounts of seeds (6,000 per plant) and has large leaves which will shade out other plants
- Contains high levels of nitrate which are poisonous to ruminant animals such as cattle and sheep
- Seeds remain viable in the soil for up to 9 years and the plant thrives in disturbance, making eradication difficult
- Thistle seeds have tiny tufts of hair (like dandelion seeds) which aid in wind dispersal
- It can be spread accidentally in cattle feed, water, mud, vehicles, machinery, erosion and by animals.