Lysimachia thyrsiflora, commonly known as tufted loosestrife, is a plant in the genus Lysimachia. It is native to large sections of the northern Northern Hemisphere, including Eurasia and North America. It often grows in marshes, shorelines of lakes and ponds and occasionally along streams. It is an erect perennial herb growing up to 80 centimeters tall and bearing yellow flowers, sometimes dotted with purple. It may be confused with purple loosestrife when not blooming but can be easily distinguished because purple loosestrife has a square stem. Tufted loosestrife has been used medicinally in Asia to combat high blood pressure.