Kingdom Plantae Tribe Senecioneae Scientific name Senecio vulgaris Rank Species | Order Asterales Genus Senecio Higher classification Ragworts | |
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Similar Ragworts, Common Chickenweed, Sonchus oleraceus, Stinking willie, Daisy family | ||
Common groundsel senecio vulgaris 2012 04 29
Senecio vulgaris, often known by the common names groundsel and old-man-in-the-Spring, is a flowering plant in the daisy family Asteraceae. It is an annual herb, native to Europe and widely naturalised as a ruderal species in suitable disturbed habitats worldwide.
Contents
Description
Senecio vulgaris is an erect herbaceous annual growing up to 16 inches (45 cm) tall. The inflorescences usually lack ray florets, the yellow disc florets mostly hidden by the bracts giving the flowers an inconspicuous appearance. Senecio vulgaris is very similar to Senecio viscosus but S. vulgaris does not have the glandular hairs and ray florets found in S. viscosus.
Upper leaves of Senecio vulgaris lack petioles and are sessile, 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, smaller towards the top of the plant. Leaves are sparsely covered with soft, smooth, fine hairs. Lobes typically sharp to rounded saw-toothed.
The hollow stems branch at the tops and from the base. Stems and leaves can both host the Cineraria leaf rust.
Open clusters of 10 to 22 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 Oxford ragwort, Senecio 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 4.2 and 4.6 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.
Common names
Vernacular names for S. vulgaris in English include old-man-in-the-spring, common groundsel, groundsel, ragwort, grimsel, grinsel, grundsel, simson, birdseed, chickenweed, old-man-of-the-spring, squaw weed, grundy swallow, ground glutton and common butterweed.
Distribution
Senecio vulgaris is considered to be native to Europe, northern Asia, and parts of North Africa. Its further distribution is less clear. 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.
Ecology
Senecio vulgaris is a frost-resistant deciduous annual plant that grows 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 distribution of this plant throughout the world has been difficult if not impossible to contain.
Herbivores
The seed of common groundsel is a good green food for canaries and finches and it is available all year round.
Senecio vulgaris seed has been found in the droppings of sparrows, and seedlings have been raised from the excreta of various birds. Seed has also been found in cow manure.
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.
Moths and caterpillars
The Senecio genus also are host to other insects:
Beetles
Flies
Seed flies (Diptera: Muscoidea)and other insects that are not listed here.
The ragwort flea beetle and ragwort seed fly have been approved and released for Senecio control in California, Australia and elsewhere.
Fungus Most Senecio, including S. squalidus are susceptible to rust and other fungus and mildews:
Rust fungus Uredinalesand other fungus that are not listed here.
Toxicity
In the U.S.A., 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.
Certain pyrrolizidine alkaloids are non-toxic precursors that are converted to toxic metabolites in the body in a process called toxification
Carl 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 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 two-year set-aside left fallow but not when there was a sown grass cover. The weed cannot live on grazed, trampled or mowed sites.
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.
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.
Groundsel seedlings with 2–6 leaves are tolerant of flame weeding but the seeds are susceptible to soil solarization.