Flower:

Loose to dense flattish clusters of bright yellow flowers, ½ to ¾ inch across with large center disks and up to 20 small rays (petals). The irregular clusters are on branched stalks at tip of main stem and upper leaf axils. Bracts and stalks are covered in short, bristly hairs.

Leaves and stems:

Leaves are 1 to 7½ inches long, ½ to 1½ inch wide, early growth leaves stalked, double lobed but soon wither away (deciduous). Stem leaves are mostly stalkless to somewhat clasping, roughly lance shaped but with wavy edges and irregular lobes, becoming smaller as they ascend the stem. Stems are hollow and crisp with strong vertical ridges and short bristly hairs, becoming more hairless with age, unbranched except for the flower clusters.

Fruit:

Seedheads mature quickly producing masses of downy bright white plumes.

Notes:

In spite of being a species of swamp, wetland and lake edges with a wide distribution of herbarium collections across Minnesota, Marsh Ragwort is not often encountered in this landscape of 10,000 water bodies. But overall distribution in North America suggests it has a strong preference for northern latitudes and may not be very tolerant of warming climate regimes. Ourselves came across a small population on the shore of Long Lake in New Brighton a few years back in a droughty spring when the lake's water level was quite low, and not seen since. Perhaps somewhat weedy in appearance, should you chance upon it, enjoy it for its own sake whilst you can! Once known as Senecio congestus it is now included with several other Thephroseris species - all with high arctic or high elevation ranges.