Description
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.
The hollow succulent stems branch at the tops and from the base. Stems and leaves can both host the Cinerarea leaf rust.
- Flowers
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 Senecio Squalidus.
- Seeds
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).
- Roots
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.
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