Alkali Marsh Butterweed, Alkali Marsh Ragwort, Great Swamp Groundsel, Water Groundsel, Water Ragwort: Senecio hydrophilus (Synonym: Senecio hydrophilus var. pacifica)

The photo above shows a close-up of one cluster of flower heads of great swamp groundsel as seen near French Glen, OR (southeastern Oregon)..........July 30, 2004. Note the narrow disks and the several short ray flowers.

Great swamp groundsel is hollow-stemmed, fibrous-rooted perennial arising from 40-200 cm in height. The herbage is smooth and often glaucous or bluish tinged. The succulent leaves are thick and firm with entire to serrate margins. The lower leaves are long-petioled with a long, narrowly elliptic blade from 10-20 cm long and 2-5 cm wide. The stem leaves are reduced in size and become sessile (as seen in the photo at right) upwards on the stem.

The flower heads are numerous and crowded. The flower heads may be entirely disk flowers, or may consist of both ray and disk flowers. When present, the rays are yellow and 4-8 mm long. The disk is narrow. The involucre is 5-8 mm tall with black-tipped bracts.

Great swamp groundsel is found in wet, swampy places at low elevations. It is tolerant of alkali conditions.

Great swamp groundsel is found from British Columbia to California, and east to Montana, South Dakota, and Colorado.

The photo above shows a cluster of great swamp groundsel as seen near French Glen, OR (southeastern Oregon)........July 30, 2004. Note the glaucous cast to the leaves and the long petioles and broadly elliptical blades of the lower leaves.

The photo above shows several of the lower leaves of great swamp groundsel as seen near French Glen, OR (southeastern Oregon)........July 30, 2004. Note the glaucous cast to the leaves and the long petioles and broadly elliptical blades of the lower leaves. The lightly toothed margins can also be seen.

The photo above shows a stem leaf of great swamp groundsel as seen near French Glen, OR (southeastern Oregon).........July 30, 2004. Note the sessile base, minutely toothed margin, and that the blades are widest at the base, tapering gradually to the tip.

The two photos above show views of the upper stem leaves and inflorescence of great swamp groundsel as seen in moist meadows along Forest Road #40 at Forest Road #277 in the Umatilla National Forest of southeastern Washington.........June 25. 2007.

Additional close-up views of great swamp groundsel as seen in wetlands at the northeastern base of Steptoe Butte in eastern Washington.........June 22, 2009.