Fringed willowherb is native to Eastern Europe, Asia, South America and North America. The plant also grows as an introduced species in several European countries, mainland Malaysia, and New Zealand. Despite not being classed as an invasive species, this plant has a weedy nature and grows in many habitats outside its preferred wetlands.

Fringed willowherb hails from North America. Known as a weed, this plant raises concern due to its swiftly multiplying nature. It possesses a unique ability to reproduce via seeds and spreads aggressively, making it difficult for other species to grow. Similarly, in gardens, this property of fringed willowherb proves detrimental as it tends to take over space rapidly and deprives native vegetation of necessary nutrients, sunlight, and water. It poses a threat to the garden's biodiversity. Its primary mode of spread is through its tiny, lightweight seeds which are numerous and can be easily carried away by wind or water currents. Notably, each plant is capable of producing up to several thousand seeds. It is this characteristic that enables fringed willowherb to invade and colonize new areas so rapidly, wreaking havoc on the local ecosystem and proving particularly problematic in gardens.

The best season to take control of the fringed willowherb plant is the late spring to early summer period. It is most effective to remove the plant during this time, ideally before it gets a chance to start flowering.