Invasive Thistles

These three thistles have similar characteristics: purple-ish flowers with thorny stems and leaves. Below are a few key differences:

European Swamp Thistle: grows up to 7’ tall with multiple flowering heads. The flowers are larger than Canada thistle, but much smaller than Bull thistle.

Bull Thistle: grows a bit shorter than EST, with multiple flower heads. The flowers are much larger and are distinctly bulb shaped.

Canada Thistle: grows smaller and shorter than both Bull and European swamp thistle, with the smallest flowering heads between the two. Canada thistle is the only perennial of the bunch, the others are biennials.