Despite its name, Canada thistle is not a plant native to Canada ... including native thistles that are not invasive, have spiny stems. This invasive thistle grows purple, puffball flowers ...

However stem elongation ("bolting") occurs when the plant produces flowers ... As with most thistles, Scotch thistle decreases animal production by reducing the amount of pasture that livestock are ...

is an invasive plant that prefers moist soils. European marsh thistle frequently invades fens, wetlands, and disturbed sites such as roadside ditches. Identifying features include: typically grows 2-7 ...