Senecio vulgaris, often known by the common name Common groundsel, a humble in appearance member of the Asteraceae family and Senecio genus, is a tenacious deciduous annual whose presence now encompasses the globe in a wide area of easy to somewhat difficult growing conditions.
The discussion of Common groundsel dates back to the 1st century and more recently, it is the subject of much contradictory and reactionary information about where it came from, how it got there, whether is it really hurting the crops, how to get rid of it, and how dangerous it is when ingested by various animals.
Standing only between 4 and 16 inches (10 to 41 cm) tall, bright florets mostly hidden by the characteristic bract giving it the appearance of never opening flowers and with a life span of 5–6 weeks, the self-fertilizing Senecio vulgaris lives humbly among and occasionally under the other weeds and is easy not to notice.
- Leaves and stems
Leaves of Senecio vulgaris grow directly from the stem, sessile or lacking their own stem (petiole), alternating in direction along the length of the plant, two rounded lobes at the base of the stem (auriculate) and sub-clasping above. Leaves are pinnately lobed and +2.4 inches (61 mm) long and 1 inch (25 mm) wide and get smaller as up the plant. Leaves are covered sparsely with soft, smooth, fine hairs. Lobes typically sharp to rounded saw-toothed.
Open clusters of 8 to 10 small cylinder shaped rayless yellow flower heads ¼ to ½ inch (6 to 13 mm) with a highly conspicuous ring of black tipped bracts at the base of the inflorescence as is characteristic of many members of the genus Senecio. There is a radiate form of Senecio Vulgaris, which is the result of cross pollination with the closely related Squalidus. 
The name for the genus Senecio is probably derived from Senex (an old man), in reference to its downy head of seeds; "the flower of this herb hath white hair and when the wind bloweth it away, then it appeareth like a bald-headed man" and like its family, flowers of Senecio vulgaris are succeeded by downy globed heads of seed. The seeds are achene, include a pappus and become sticky when wet. Laboratory tests have suggested maximum seed scattering distances of 2.1 and 3.2 yd (1.9 and 2.9 m) at wind speeds of 6.8 and 10.2 mph (10.9 and 16.4 km/h) respectively (affected by plant height) suggests that it was more than wind that spread these groundsel seeds throughout the world.
The average weight of 1000 seeds is 0.21 gram (2,200,000 seeds per pound) and experienced a 100% germination success before drying and storage and an 87% germination success after drying and 3 years of cool dry storage. In simple models for seed emergence prediction, soil thermal time did not predict the timing and extent of seedling emergence as well as hydrothermal time (warm rain).
The root system consists of a shallow taproot. This plant spreads by reseeding itself.
Groundsel acts as a host for the fungus that causes black root rot in peas, alfalfa, soybeans, carrots, tomatoes, red clover, peanuts, cucurbits, cotton, citrus, chickpeas, and several ornamental flowering plants; a list of flowering plants that can host their own fungus as well.
Senecio vulgaris is a frost resistant deciduous annual plant that grows willingly in disturbed sites, waste places, roadsides, gardens, nurseries, orchards, vineyards, landscaped areas, agricultural lands, at altitudes up to 1,600 feet (500 m) and is, additionally, self-pollinating producing 1,700 seeds per plant with three generations per year. Seeds are dispersed by wind and also cling to clothing and animal fur, and as contaminates of commercially exchanged seeds; the relocation of this plant throughout the planet has been difficult if not impossible to contain.
There is conflicting information about the native status of Senecio vulgaris in various locations. The United States Department of Agriculture (USDA), Natural Resources Conservation Service Plants Profile Database considers it to be native to all 50 of the United States of America, Canada, Greenland, Saint Pierre and Miquelon, the same USDA through the Germplasm Resources Information Network (GRIN) considers it to be native only to parts of Afro-Eurasia. The Integrated Taxonomic Information System Organization (ITIS), a partnership between many United States federal government departments and agencies states that the species has been introduced to the 50 United States, and the online journal Flora of North America calls it "probably introduced" to areas north of Mexico. Individual research groups claim it is not native to areas they oversee: Florida, Washington, Wisconsin, Saskatchewan, British Columbia, Missouri. The United States Geological Survey reports that Common Groundsel is exotic to all 50 states and all Canadian provinces with the exception of Georgia, Kentucky, Massachusetts, and Labrador.
- Senecio vulgaris is considered to be native to Algeria, Libya, Morocco, Tunisia, Georgia, Republic of Adygea, Karachay–Cherkess Republic, Kabardino-Balkaria Republic, Republic of North Ossetia–Alania, Republic of Ingushetia, Chechen Republic, Republic of Dagestan, Amur Oblast, Chukotka Autonomous Okrug, Jewish Autonomous Oblast, Kamchatka Oblast, Koryak Autonomous Okrug, Khabarovsk Krai, Magadan Oblast, Primorsky Krai, Sakha (Yakutia) Republic, Sakhalin Oblast, South Korea, North Korea, Denmark, Faroe Islands, Finland, Iceland, Ireland, Norway, Sweden, United Kingdom, Austria, Belgium, Czech Republic, Slovakia, Germany, Hungary, Netherlands, Poland, Switzerland, Belarus, Estonia, Latvia, Lithuania, Moldova, Russian Central Federal District, Russian Southern Federal District, Ukraine, Albania, Bulgaria, Greece, Italy, Romania, Bosnia and Herzegovina, Croatia, the Republic of Macedonia, Montenegro, Serbia, and Slovenia, France and Portugal.
- Western Asia: Iran, Israel with the Palestinian territories, Lebanon and Syria.
- Caucasus: Adygea, Azerbaijan, Chechnya, Dagestan, Georgia, Ingushetia, Kabardino-Balkaria, Kalmykia, Karachay–Cherkessia, North Ossetia–Alania
- Northwestern Asia: Arkhangelsk Oblast including Nenets Autonomous Okrug and Novaya Zemlya, Astrakhan Oblast, Bashkortostan, Belgorod Oblast, Bryansk Oblast, Chuvashia, Lipetsk Oblast, Kaliningrad Oblast, Kaluga Oblast, Novgorod Oblast, Republic of Karelia, Kirov Oblast, Komi Republic, Kursk Oblast, Mordovia, Murmansk Oblast, Orenburg Oblast, Penza Oblast, Perm Krai, Pskov Oblast, Rostov Oblast, Ryazan Oblast, Saint Petersburg, Samara Oblast, Saratov Oblast, Tambov Oblast, Tatarstan, Tula Oblast, Udmurtia, Volgograd Oblast, Vologda Oblast, Voronezh Oblast,
- Siberia: Altai Krai, Buryatia, Chelyabinsk Oblast, Chita Oblast, Irkutsk Oblast, Kemerovo Oblast, Krasnoyarsk Krai, parts of Kurgan Oblast, Novosibirsk Oblast, Omsk Oblast, Sverdlovsk Oblast, Tomsk Oblast, Tuva, Tyumen Oblast, Ulyanovsk Oblast, Yamal-Nenets,
- Soviet Far East: Amur Oblast, Chukotka Autonomous Okrug, Jewish Autonomous Oblast, Kamchatka Oblast, Koryak Autonomous Okrug, Khabarovsk Krai, Magadan Oblast, Primorsky Krai, Sakha (Yakutia) Republic, Sakhalin Oblast
- China: Inner Mongolia, Heilongjiang, Jilin, Liaoning, Hebei and Beijing
- Eastern Asia: South Korea, North Korea, Hokkaidō, Honshū, Shikoku, Kyūshū, Okinawa Island
- Northern Europe: Channel Islands, Denmark, Estonia, Faeroe Islands, Finland, Iceland, Ireland with Northern Ireland, Norway, Sweden, United Kingdom
- Middle Europe: Austria, Czech Republic, Germany, Poland, Slovakia, Slovenia,
- East Europe: Belarus, Hungary, Latvia, Lithuania, Moldavia, Ukraine
- Southeastern Europe: Bosnia and Herzegovina, Bulgaria, Croatia, Republic of Macedonia, Montenegro, Romania, Serbia
- Southwestern Europe: Andorra, Azores, Balearic Islands, Canary Islands, Gibraltar, Portugal, Spain
- West Europe: Belgium, France, Liechtenstein, Luxembourg, Netherlands, Switzerland,
- South Europe: Albania, Chios, Corsica, Crete, Cyprus, Dodecanese, Greece, Ikaria, Italy, Karpathos, Lesbos, Samos Island, San Marino, Sardinia, Sicily with Malta, Asiatic Turkey and Turkey-in-Europe, Vatican City
- North America: United States, Greenland, Saint Pierre and Miquelon
- Canada: Alberta, British Columbia, Manitoba, New Brunswick, Newfoundland and Labrador, Northwest Territories and Nunavut (not collected North of the Hudson Bay), Nova Scotia, Ontario, Prince Edward Island, Quebec, Saskatchewan, Yukon.
- Mexico: Aguascalientes, Baja California Norte, Chiapas, Coahuila, Distrito Federal, Hidalgo, Jalisco, Estado de México, Nuevo León, Puebla, Tlaxcala, Veracruz
- Oceania: New Zealand
- South America: Argentina, Bolivia, Chile, Ecuador, Peru
- Range maps for continents
Some Lepidoptera species eat many of the Senecio genus; additional studies via electrophysiological recordings have shown that the taste sensilla of the Cinnabar moth larvae respond (get excited) specifically to the pyrrolizidine alkaloids, which all Senecio are known to contain.
- Cinnabar moth (Tyria jacobaeae)
- Flame Shoulder (Ochropleura plecta)
- Ragwort plume moth (Platyptilia isodactyla)
- Ragwort flea beetle (Longitarsus jacobaeae)
- Longitarsus gracilis (family Coleoptera species Chrysomelidae)
- Seed flies (Diptera: Muscoidea)
- Gall flies (Diptera: Tephritidae):
and other insects that are not listed here.
- Rust fungus Uredinales
- White rust Peronosporales
- Sac fungus Ascochyta, Pezizomycetes
- Groundsel Mildew Erysiphales
- Powdery Mildew Erysiphales
- Black root rot Microascales
- some of the family Incertae sedis
and other fungus that are not listed here.
Reputation for being noxious and toxic
Senecio vulgaris has been listed as a noxious weed, being both non-indigenous to most if not all of the Americas and having a reputation for being hepatotoxic to livestock and to humans.
Toxic versus medicinal
As a plant that is reported to be both poisonous for human ingestion and also medicinal; much of the contradiction can be found by closely reviewing the words that are used and the dose (amount) of the poisonous substance that is ingested to prove either claim. All species of the genus Senecio contain pyrrolizidine alkaloids (e.g., senecionine) a substance that when a human has chronic exposure can cause irreversible liver damage.
Common groundsel as a medicinal herb does not seem to be recommended very often since 1931, when it was recommended as a diaphoretic, an antiscorbutic, a purgative, a diuretic and an anthelmintic, which was a demotion as it was previously suggested for the expelling of gravel of the kidneys and reins by Pedanius Dioscorides in the 70s-90s, for use as poultices by John Gerard in the late 16th century and as a cure for epilepsy by Nicholas Culpeper in the 17th century. More current information is contradictory about the dangers of the ingestion of Groundsel. A heavily referenced paper from 1989 suggests that the response is immediate and gives pre-ambulatory care recommendations. A Canadian poisonous plants information database references a paper from 1990 in presenting this prenatal warning: "In a case of prenatal exposure, a mother ingested tea containing an estimated 0.343 milligram of senecionine, resulting in fatal veno-occlusive disease in a newborn infant." Information about the pyrrolizidine alkaloids, the substance present in Senecio vulgaris is much less contradictory and all warn of accumulation of the alkaloid.
Linnaeus is cited to have claimed that "goats and swine eat this common plant freely, cows being not partial to it and horses and sheep declining to touch it, but not only are caged birds fond of it (the seeds), but its leaves and seeds afford food for many of our wild species (rabbits were given as an example)." More recent studies claim that the lethal amount that cattle or horses need to consume is 7% of their body weight (example: 50 pounds (23 kg) would need to be consumed by a cow weighing 700 pounds (318 kg)). Lesser amounts cause the liver to lose function but is not apparent until the animal is stressed (by new feed or location, pregnancy, a different toxin, etc.). Sheep and goats have rumen bacteria that detoxify the alkaloids and are able to consume twice their body weight of this and other species of genus Senecio. The alkaloids responsible are not destroyed by drying or by fermentation in silage.
Introduced versus invasive
Introduced species become invasive when they compete with natives or with crops. Senecio vulgaris is not known to be a strong competitor but it has been known to reduce mint production. There is evidence that it is not a strong invasive and sometimes protective of critically endangered native plants.
The approximately 22 millimetres (0.87 in) long pappus seeds of Senecio vulgaris, each plant capable of producing 25,000 or more seeds (1,700 seeds per plant are more likely) with three generations of the plant per year; seeds that are widely dispersed by the wind, have been identified as a contaminant of cereal and vegetable seeds and a poison to some livestock; there is some inspiration to understand the growth stages and determine some control methods.
- Cultivation: Cultivation with the hand or tiller is a recommended method of controlling Senecio vulgaris from growing in gardens and planting fields; cultivate to a depth of 2 inches (51 mm). The plant does prefer to take root in disturbed soils, so cultivation rids new plants but also buries and stirs up new seeds so the cultivation needs to be repeated at 14-day intervals. Seeds can still mature even when the plant has been killed; seed from plants cut in flower had germination levels of 35%. Groundsel seed numbers increased in soil during a 2-year set-aside left fallow but not when there was a sown grass cover. The weed cannot live on grazed, trampled or mowed sites.
- Biological: The pathogen rust fungus or Puccinia lagenophorae and the Cinnabar moth Tyria jacobaeae have both been used and studied in an attempt to control infestation of Senecio vulgaris. One study showed that rust fungus infected Senecio vulgaris survived and actually used more of the available soil nutrients. The cinnabar moth eats groundsel between June and August, but the seeds germinate and the plant grows as soon as the ground is warm enough (and after a warm rain), making this an insufficient control almost everywhere groundsel can be found.
- Chemical: Herbicides designed to control broadleaf plants are affective for controlling Senecio vulgaris in cereals and forage grasses but also will "control" broadleaf crops, such as mint, forage legumes, strawberries, carrots and all other non-grass crops. There is also evidence that the plant develops an immunity to the chemical control.
- Other: Groundsel seedlings with 2-6 leaves are tolerant of flame weeding but the seeds are susceptible to soil solarization.
- Senecio vulgaris subsp. denticulatus (O.F. Muell.) P.D. Sell
- Senecio vulgaris var. dubius (Ledeb.) Franch., 1883
- Senecio vulgaris var. dubius Trautv., 1866
- Senecio vulgaris var. hibernicus Syme
- Senecio vulgaris var. vulgaris
- Senecio vulgaris-humilis Batt. & Trab.
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