Bull Thistle (Cirsium vulgare) Division - Magnoliaphyta Class - Magnoliopsida Subclass - Asteridae Order - Asterales Family - Asteraceae Genus - Cirsium Bull thistle has smaller heads than musk thistle. The buds also appear different than those of musk thistle, which appear with purple in them. Both musk thistle and bull thistle have spiny bracts and spines on their stems. Canada thistle does not have either. Weeds Taxonomic List List by Scientific Name List by Common Name