Milk thistle (Silybum marianum ... Milk thistles' large, spiny, dark-green leaves have white marbling, which is where the plant gets its common name from, explains Amy Enfield of ScottsMiracle ...

Canada thistle is a colony-forming perennial from deep and extensive horizontal roots. Stems are 1 to 4 feet tall, ridged, branching above. Leaves are alternate, lacking petioles, oblong or ...

European marsh thistle frequently invades fens, wetlands, and disturbed sites such as roadside ditches. Identifying features include: typically grows 2-7 feet tall leaves are alternate with deeply ...