Appearance
Like all members of the family Asteraceae, ''Senecio squalidus'' has a composite flower head known as a capitulum. What look like single flowers are actually a cluster of florets, each petal or ligule being a flower, or floret, possessing its own stamen and capable of producing the specialized seed of the family Asteraceae, the parachute-like achene.Oxford ragwort is a short-lived perennial, a biennial, or a winter annual and grows in a branched straggling form to between 1.5 feet and 3.3 feet depending on conditions. ''S. squalidus'' prefers dry, disturbed places, cultivated and waste ground, walls and railway banks. It flowers from March to December
and reproduces from seed.
Leaves and stems: ''S. squalidus'' leaves are alternate, glossy, almost hairless and variable in form from deeply pinnately lobed to undivided with only the lower leaves being stalked. Stems and leaves resemble those of the common groundsel with the exception that their lobes are more widely spaced.
Inflorescence: ''S. squalidus'' has larger capitula than ''Senecio jacobaea'' and a more spreading habit. Yellow capitula of 10-14 petals in loose clusters. They are pollinated by insects. Ray corollas .3 inches to .6 inches long, .08 inches to .16 inches wide.
Oxford ragwort is self-incompatible and needs pollen from other plants with different self-incompatibility alleles. Its own flower possess a stigma with characteristics of both the “dry” and “wet” types.
The fruiting heads are often nodding.
Seeds: Each pollinated Oxford ragwort floret matures into a bell to cylindrical shaped indehiscent achene, the shallowly ribbed fruit is light brown in colour and .06 inches to .12 inche long. Each plant can produce approximately 10,000 fruits during the year.
As a ''Senecio'' and a diploid ''Senecio squalidus'' is part of a species group along with ''S. flavus'', ''S. gallicus'', ''S. glaucus'' and ''S. vernalis'', which are widespread geographically and interesting for the study of genetic differences in relation to the environment and plant evolution.
Naming
*''Jacobaea incisa'' C. Presl⤷ ''Senecio glaber'' Ucria
⤷ ''Senecio incisus'' C. Presl
⤷ ''Senecio laciniatus'' Bertol.
⤷ ''Senecio nebrodensis'' auct., non L.
⤷ ''Senecio rupestris'' Waldst. & Kit.
⤷ ''Senecio squalidus'' d'Urv.
⤷ ''Senecio squalidus'' Willd.
⤷ ''Senecio squalidus'' M.Bieb.
⤷ ''Senecio nebrodensis'' L. subsp. ''rupestris'' Fiori
⤷ ''Senecio leucanthemifolius'' subsp. ''vernalis'' Greuter
⤷ ''Senecio squalidus'' subsp. ''aethnensis'' Greuter
⤷ ''Senecio squalidus'' subsp. ''araneosus'' Alexander
⤷ ''Senecio squalidus'' subsp. ''aurasicus'' Alexander
⤷ ''Senecio squalidus'' subsp. ''aurasiacus'' Alexander
⤷ ''Senecio squalidus'' subsp. ''chrysanthemifolius'' Greuter
⤷ ''Senecio squalidus'' subsp. ''eurasiacus'' Alexander
⤷ ''Senecio squalidus'' subsp. ''microglossus'' Arcang.
⤷ ''Senecio squalidus'' subsp. ''rupestris'' Greuter
⤷ ''Senecio squalidus'' subsp. ''sardous'' Greuter
⤷ ''Senecio squalidus'' subsp. ''squalidus''
⤷ ''Senecio squalidus'' var. ''glaber'' FIORI
;Misapplied names:
⟶ *''Senecio nebrodensis'' sec. Fiori, A
References:
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