About Senecio rupestris Waldst. & Kit.
This entry refers to Senecio rupestris Waldst. & Kit., and the description below covers Senecio squalidus, commonly known as Oxford ragwort. Like all members of the Asteraceae family, Senecio squalidus produces composite flower heads called capitula. Structures that appear to be single flowers are actually clusters of florets; each petal or ligule is an individual floret that has its own stamen and can produce the family's characteristic specialized seed, a parachute-shaped achene. Oxford ragwort can be a short-lived perennial, a biennial, or a winter annual. It grows in a branched, straggling form, reaching between 0.5 m (1.5 feet) and 1 m (3.3 feet) tall depending on growing conditions. S. squalidus prefers dry, disturbed sites, including cultivated ground, waste ground, walls, and railway banks. It flowers from March to December and reproduces by seed. The leaves of S. squalidus are alternate, glossy, and almost hairless. They vary in form from deeply pinnately lobed to undivided, and only lower leaves have stalks. Stems and leaves of S. squalidus resemble those of common groundsel (Senecio vulgaris), except the leaf lobes are more widely spaced. S. squalidus has larger capitula than Senecio jacobaea and a more spreading growth habit. Its yellow capitula, each holding 10 to 14 florets, are arranged in loose clusters, and they are pollinated by insects. Ray corollas measure 8 mm (0.3 inches) to 15 mm (0.6 inches) long, and 2 mm (0.08 inches) to 4 mm (0.16 inches) wide. Oxford ragwort is self-incompatible, meaning it requires pollen from other plants that carry different self-incompatibility alleles to reproduce. Its stigmas have traits of both 'dry' and 'wet' stigma types. Fruiting heads are often nodding. Each pollinated floret of Oxford ragwort matures into a bell- to cylindrical-shaped indehiscent achene. This shallowly ribbed fruit is light brown, and measures 1.5 mm (0.06 inches) to 3 mm (0.12 inches) long. A single plant can produce roughly 10,000 fruits in one year. As a diploid member of the genus Senecio, S. squalidus is part of a species group that also includes S. flavus, S. gallicus, S. glaucus, and S. vernalis. This group is geographically widespread, and is of interest for studying genetic differences related to environment and plant evolution. In its native range, Senecio squalidus grows on scree in mountainous areas. It got its common name Oxford ragwort due to its ability to readily grow in similar rocky, disturbed habitats across the world. There are conflicting accounts of its native origin from USDA resources: the USDA Natural Resources Conservation Service lists it as native to New Brunswick and Nova Scotia, Canada, while the USDA Germplasm Resources Information Network lists it as native to Austria, Czech Republic, Slovakia, Germany, Switzerland, Albania, Bulgaria, Greece, Crete, Italy, Sardinia, Sicily, Romania, Bosnia and Herzegovina, Croatia, Montenegro, North Macedonia, Serbia, and Slovenia. Its current distribution is as follows: Africa: Northern Africa (Morocco); America: North America (New Brunswick, Nova Scotia, British Columbia, California); Europe: Northern Europe (Denmark, Germany, Republic of Ireland, Netherlands, Norway, Sweden, United Kingdom); Middle Europe (Austria, Czech Republic, Hungary, Slovakia, Switzerland); East Europe (Poland); Southeastern Europe (Albania, Bosnia and Herzegovina, Bulgaria); Southwestern Europe (France, Spain); South Europe (Croatia, Crete, Greece, Italy, North Macedonia, Romania, Sardinia, Serbia, Sicily, Slovenia). This entry includes range maps.
