Senecio hydrophiloides, commonly known as tall groundsel or sweet marsh ragwort, is a biennial or perennial herb that is native to riparian zones, wet meadows, and marshy areas in western North America, ranging from British Columbia and Alberta down to northern California and Utah. It can exceed one meter in height and features lance-shaped to oval leaves along its erect stem. From late spring to early fall, it produces dense clusters of small, bright yellow flower heads that are attractive to a variety of pollinators. The flowers are modest in size but can be quite showy due to their profusion.

Tall groundsel is valued for its ability to thrive in wet conditions and is often used in restoration projects and naturalized plantings where moisture is abundant. It is also suitable for rain gardens and as a border plant in water-wise landscaping. In cultivation, it requires consistently moist soils and can tolerate a range of light conditions from full sun to partial shade. While it is generally low-maintenance, it is important to note that Senecio hydrophiloides contains pyrrolizidine alkaloids and can cause dermatitis in some individuals upon contact. It should be handled with care, and its placement should be considered to avoid high-traffic areas where skin contact is likely.CC BY-SA 4.0