Californian Thistle thrive in areas where sunlight intensity is moderate, temperatures are moderate, and ground water is plentiful. Given its adaptive nature, Californian Thistle is one of the worst invasive weeds worldwide. Through comparison of its genetic expressions, the plant evolves differently with respects to where it has established itself.
Californian Thistle is a sign of a critical state of soil health. It is often present in soils where anaerobic bacteria are dominant. Water and move poorly in the soil and beneficial microbes struggle to survive. Calcium and Potassium levels are low, while Iron levels are high.