Senecio congestus

Like many of the Senecio genus S. congestus can be an annual or biennial and perhaps rarely perennial, depending on the conditions.[2] A villous broad leafed plant with a single[7] hollow stem and favoring mud flats like Marsh Groundsel (Senecio hydrophilus) but not alike in that marsh ragwort cannot tolerate alkaline sites nor standing water.[8]

In the early stages of growth, the leaves, stem, and flower heads are all covered with translucent hairs, producing a "greenhouse effect" close to the surface of the plant, essentially extending the growing season by a few vital days by allowing the sun to warm the tissues, and preventing the heat from escaping.[9]

Leaves and stems: An erect plant [7] standing 6 to 60 inches (15 to 150 cm) tall, S. congestus varies as much in stature as it does in the distribution and the persistence of its tomentum (the closely matted or fine hairs on plant leaves).[2] Sparse to dense villous stems are more hollow towards the base;[8] hairs that are white, light yellowish, or reddish brown.[2] Basal and cauline[2] leaf edges mostly toothless or with a few coarse teeth[7] that sometimes wither before flowering.[2] The leaves all basically similar in shape, oblong with the lower ones often spatulate, 1.6 to 8 inches (4 to 20 cm) long, 0.2 to 2.5 in (0.5 to 6 cm) wide, with the basal leaves occasionally larger, glabrous or villous in patches, rounded at the tips, toothed, often deciduous with clasping bases.[8]

Flowers: "Congested" clusters of several to many pale yellow flower heads[8] that sometimes appear tubular and incompletely opened.[2] a branched inflorescence,[7] with 13 to more than 21 flower heads per stalk. Each flower head is ¼ to ½ inch (6 to 13 mm) across and 0.16 to 0.4 inch (0.4 to 10 mm) in length,[2] with small but obvious rays[7] in a corolla laminae surrounded by (usually) 21 green or yellowish green, pink tipped bracts[2] which can be scarious toward the tips.[8]

Seeds: Typical of the genus Senecio, S. congestus produces strongly accrescent[8] one-seeded, one-celled,[2] 1.5 to 2.5 millimetres long[8] dry achenes[7] on very fine & numerous,[8] white or dirty white,[2] fluffy,[7] pappus bristles.[8] The seeds have been shown to survive in the soil for more than a year but less than 5 years, the maximum longevity unknown.[10]

Roots: Fibrous and without a tap root.[8]

Senecio congestus plants itself in areas that have freezing winters[1] and in moist to wet soils, such as damp meadows, swamps, sandy pond edges[7] and roadside ditches[11] at altitudes of 0 to 3,300 feet (1,000 m)[2] It is the most common annual plant species in the eastern Canadian Arctic.[9]

Native[1][12]

America

North America: Alaska, Iowa, Michigan, Minnesota, North Dakota, South Dakota, Wisconsin, British Columbia, Alberta, Saskatchewan, Manitoba, Ontario, Quebec, New Brunswick, Nova Scotia, Prince Edward Island, Newfoundland and Labrador, Yukon, Northwest Territories, Nunavut

Asia

Northwestern Asia: Astrakhan Oblast, Bashkortostan, Belgorod Oblast, Bryansk Oblast, Chuvashia, Franz Josef Land, Kalmykia, Kaluga Oblast, Kirov Oblast or Vyatka, Kursk Oblast, Lipetsk Oblast, Mordovia, Novgorod Oblast, Novaya Zemlya, Orenburg Oblast, Penza Oblast, Perm Krai, Pskov Oblast, Rostov Oblast, Ryazan Oblast, Saint Petersburg, Samara Oblast, Saratov Oblast, Tambov Oblast, Tatarstan, Tula Oblast, Ulyanovsk Oblast, Udmurtia, Volgograd Oblast, Voronezh Oblast

Europe

Northern Europe: Denmark, Estonia, Latvia, Sweden

Middle Europe: Czech Republic, Poland

East Europe: Belarus, Kaliningrad Oblast, Lithuania, Ukraine

West Europe: France, Luxembourg, Netherlands

Southeastern Europe: Croatia

Current[1][12]

America

North America: Alaska, Iowa, Michigan, Minnesota, North Dakota, South Dakota, Wisconsin, British Columbia, Alberta, Saskatchewan, Manitoba, Ontario, Quebec, New Brunswick, Nova Scotia, Prince Edward Island, Newfoundland and Labrador, Yukon, Northwest Territories, Nunavut

Asia

Northwestern Asia: Astrakhan Oblast, Bashkortostan, Belgorod Oblast, Bryansk Oblast, Chuvashia, Franz Joseph Land, Kalmykia, Kaluga Oblast, Kirov Oblast or Vyatka, Kursk Oblast, Lipetsk Oblast, Mordovia, Novgorod Oblast, Novaya Zemlya, Orenburg Oblast, Penza Oblast, Perm Krai, Pskov Oblast, Rostov Oblast, Ryazan Oblast, Saint Petersburg, Samara Oblast, Saratov Oblast, Tambov Oblast, Tatarstan, Tula Oblast, Ulyanovsk Oblast, Udmurtia, Volgograd Oblast, Voronezh Oblast

Europe

Northern Europe: Denmark, Estonia (decreasing), Latvia, Sweden

Middle Europe: Czech Republic, Poland, Slovakia

East Europe: Belarus, Kaliningrad Oblast, Lithuania, Ukraine

West Europe: Belgium, France, Luxembourg, Netherlands

Southeastern Europe: Croatia

Southwestern Europe: Andorra, Gibraltar, Spain

Range maps

• 
  North America
• 
  Europe
• 
  Russia

Toxicity: Unlike many in the Senecio genus, marsh ragwort is considered a vegetable and safe for human consumption;[13] the young leaves and flowering stems of Senecio congestus can be eaten raw as salad, cooked as a potherb or made into a "sauerkraut",[14]

Noxiousness: Senecio congestus does appear on a list of North Dakota plants to be monitored,[6] however, it tends to be more of a plant the presence of which indicates severe disturbance such as over-foraging and hyper-salinity, as is the case of the habitats of arctic geese where the forage plants are disappearing. Two locations are mentioned by United States Fish and Wildlife Service (USFWS) having problems from the ever-expanding populations of arctic geese[15] and one from the Arctic Institute of North America of the University of Calgary[16] or from an unpublished report from the Canadian Wildlife Service made available by the USFWS:[17]

• Akimiski Island in the Canadian Northwest Territories where swards of Puccinellia phryganodes and Carex subspathacea have been replaced with dead willow stands and mudflats growing non-forage plant species, including Glaux maritima and Senecio congestus
• Cape Churchill Region and La Pérouse Bay, Manitoba where the expanding population of lesser snow geese has resulted in substantial changes to all intertidal habitats. In the vicinity of the coast extensive moss carpets are present and Senecio congestus and Salicornia borealis are widespread.
• Karrak Lake,[18] Nunavut where growth in populations of Ross's geese (Chen rossii) and lesser snow geese (Chen caerulescens) has led to a decline in vegetative cover and areas with a 10-year or longer history of goose nesting than in areas with less than 10 years of nesting had more instance of exposed mineral substrate, exposed peat, and Senecio congestus.

Senecio congestus is reported to be extirpated in Michigan.[1]

• Media related to Tephroseris palustris at Wikimedia Commons
• Data related to Senecio congestus at Wikispecies