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.
Flower heads can appear as a small clump or solitary at the apex of a stem. Blooms spring to early fall. Bull thistle seeds are numerous and straw-colored. The seeds are one tenth to two tenths of an ...
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 ...