Description
Like all members of the large Asteraceae family, Senecio squalidus has a flower head. Where this is joined to the plant stem there are bracts and what look like single flowers are actually a cluster or inflorescence, known as a capitulum, with each petal or corolla being its own 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 (0.5 m) and 3.3 feet (1 m) depending on conditions. S. squalidus prefers dry, disturbed places, cultivated and waste ground, walls and railway banks, flowering from March to December and reproduces from seed.
- Leaves and stems
- S. squalidus have herbaceous plants whose alternate, glossy and varying from deeply pinnately lobed to undivided leaves are almost hairless with only the lower ones being stalked. Stems and leaves resemble those of the Common Groundsel (Senecio vulgaris) with the exception that their lobes are more widely spaced.
- Inflorescence
- S. squalidus has larger more attractive capitula than Senecio jacobaea and a more spreading habit. Yellow capitula of 10-14 petals in loose clusters at the stem. The tips are pollinated by insects. Ray corollas .3 inches (8 mm) to .6 inches (15 mm) long, .08 inches (2 mm) to .16 inches (4 mm) 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 corolla matures into a bell to cylindrical shaped indehiscent achene, the shallowly ribbed fruit is light brown in colour and .06 inches (1.5 mm) to .12 inches (3 mm) long. Each plant can produce approximately 10,000 fruits during the year.
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Mature Capitulum
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S. squalidus developing capitula.
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Leaves and stalks of S. squalidus.
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Capitula at different stages of development
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 who are widespread geographically and interesting for the study of genetic differences in relation to the environment and plant evolution.
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