Policeman’s helmet forms dense patches that begin in open, disturbed areas, especially streams. Once established, policeman’s helmet easily moves into undisturbed, high-value habitat. These dense patches reduce plant and animal diversity as they choke out other species. They also increase stream bank erosion and increase the possibility of landslides.

Policeman’s helmet spreads primarily by seed, but it is also capable of rooting wherever the stem touches soil. Management is relatively easy, though it requires extra attention to detail. Missing a few plants sometimes means returning to square one.