Marsh fleabane – Tephfroseris palustris

Alaska Wildflowers | Yellow

The yellow flowers of the marsh fleabane (Tephroseris palustris), also known as the mastodon flower on Murphy Dome in Fairbanks, Alaska

Marsh fleabane

Tephroseris palustris

Common Names

clustered marsh ragwort
clustered marsh squaw-weed
marsh fleabane
marsh ragwort
mastodon flower


Senecio congestus
Senecio palustris
S. congestus ssp. tonsus
S. congestus var. palustris
S. congestus var. tonsus
Cineraria congesta


none – the synonym Senecio congestus had 3 listed subspecies (ssp. tonsus, var. palustris, and var. congestus) all of which are contained under T. palustris

Genus: Tephroseris
Family: Asteraceae
Order: Asterales
full classification

Duration – Growth Habit

Annual or Biennial – Forb/herb

Identification and Information

Marsh fleabane (also commonly called mastodon flower) is a yellow-flowering annual or biennial herb that grows from fibrous roots (no caudex or underground stems). The aerial stem is solitary, hollow, are covered in short white hairs, and often fairly thick.

It has both basal and cauline leaves that are often narrow with toothed margins (often coarsely dentate), although are highly variable and often heterophyllous (leaves can be different on the same plant). The basal leaves sometimes wither before the plant flowers. Leaf petioles may not be present or be poorly defined. The leaf blades are oblanceolate (rounded apex and a tapered base) to linear-oblanceolate or spatulate (broad apex and narrow base, like a spatula). Like the stem, the leaves are also often covered in fine white hair.

The inflorescence is composed of several flowering heads that may be either loose or crowdedly arranged in a corymbiform array. The flowers have involucral bracts typically with 21 lanceolate green or yellowish-green phyllaries. The flower heads are yellow, 8-20 mm deep and 12-20 mm wide, with both disk florets (30-50) and ray florets (13-21). The flowers have 5 yellow stamens with yellow anthers and an inferior ovary with 2 carpels, the single style is 7-8 mm long and has 2 stigmas.

Previously there were considered to be multiple species and subspecies of Tephroseris palustris, varying in stature, wool, and leaf shape. Currently, these are treated as a single polymorphic species.


For information only (typically historical) – I take no responsibility for adverse effects from the use of any plant.

The plant (especially the root) is considered poisonous by the Inuktitut. Porsild (1953) describes in Edible Plants of the Arctic that the “Eskimo of northwestern Alaska” (probably Inupiaq) ate the leaves and flowering stems as a salad or were made into sauerkraut. Most flowers in the genera Senecio and Tephroseris contain alkaloid senecionine which can lead to liver damage and/or cancer over time and is considered toxic in large quantities to humans and livestock.

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Distribution and Habitat

Marsh fleabane has a widespread circumboreal distribution across North America and Eurasia. In North America, it is found in Alaska, most of Canada, and some northern midwest states in the contiguous US. It is considered vulnerable in British Columbia and Iowa, and critically imperiled in Wisconsin and Newfoundland (it is not found in Labrador, but Newfoundland and Labrador are treated as a single unit in this mapping app).

This plant prefers wet habitats. It is frequently found in marshes, wet meadows, seashores, and mossy or wet tundra.


RankScientific Name (Common Name)
KingdomPlantae (plantes, Planta, Vegetal, plants)
   SubkingdomViridiplantae (green plants)
      InfrakingdomStreptophyta (land plants)
            DivisionTracheophyta (vascular plants, tracheophytes)
               SubdivisionSpermatophytina (spermatophytes, seed plants, phanérogames)
                           FamilyAsteraceae (sunflowers, tournesols)
                              GenusTephroseris (Rchb.) Rchb. (groundsel)
                                 SpeciesTephroseris palustris (L.) Reichenbach (marsh fleabane)

References and Further Reading


Field Guide to Alaskan Wildflowers, Pratt, Verna E. pg 43

Classification and Taxonomy

T. palustris (L.) Reichenbach Taxonomic Serial No.: 780534, ITIS Database

S. congestus (R. Br.) DC., USDA Database


S. congestus (R. Br.) DC., Native American Ethnobotany Database

Porsild, A.E., 1953, Edible Plants of the Arctic, Arctic 6:15-34, page 27

Map and Distribution

T. palustris (L.) Fourr. Published in: Fourr. In: Ann. Soc. L. Lyon, N. S. 16: 404. (1868)., GBIF Database

Description and Information

T. palustris (L.) Fourr. subsp. congesta (R. Br.) Holub, Flora of the Canadian Arctic Archipelago

T. palustris (Linnaeus) Reichenbach, Fl. Saxon. 146. 1842., Flora of North America


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