When it comes to common weeds, few are as problematic as Canada thistle. This plant has a tenacious and fast-growing root system. A single seed is all it takes for an entire patch to spring up and ...

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, a terrestrial and wetland herbaceous biennial in the Asteraceae family, is an invasive plant that prefers moist soils. European marsh thistle frequently invades fens, wetlands, ...

Sow thistle is commonly found in crops, gardens and waste areas. As with many members of the Asteraceae family, it starts life as a rosette, and then bolts to form an upright flower stem. Sow thistle ...

Californian thistle is one of the most common thistle species in New Zealand. It is very troublesome in pastures because it is so difficult to control. Once a plant is established in pasture, it forms ...