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I know it as Spear Thistle. I have never heard of Bull Thistle...I would be interested to know if that is commonly used for the species?
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It's Spear Thistle in my neck of the woods. Bull Thistle is a new one for
'Bull thistle' is the North American name for it.
Lat/Lng: 51.8, -3.2
OS grid ref: SO1912