Bull thistle starts out life as a prickly ground-hugging rosette that, in the summer, puts out tall, equally spiny stalks topped with purple flowers. Later, fluffy white seed heads form.

Like many other biennial invasives, bull thistle is able to produce a large seed bank that can remain viable for up to 10 years! As a result, the plant can easily spread and form dense stands in ...

They reproduce via seeds only. If you see one, take immediate action to get rid of it. “Bull thistle is considered noxious in ...