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Scotch Thistle

Onopordum acanthium

Description:

A flowering plant in the family Asteraceae. It is native to Europe and western Asia from Iberia east to Kazakhstan, and north to central Scandinavia, and widely naturalised elsewhere. It is a vigorous biennial plant with coarse, spiny leaves and conspicuous spiny-winged stems. It produces a large rosette of spiny leaves the first year. The plants typically germinate in the autumn after the first rains and exist as rosettes throughout the first year, forming a stout, fleshy taproot that may extend down 30 cm or more for a food reserve. In the second year, the plant grows (0.2–) 0.5–2.5 (–3) m tall and a width of 1.5 m. The leaves are 10–50 cm wide, are alternate and spiny, often covered with white woolly hairs and with the lower surface more densely covered than the upper. The leaves are deeply lobed with long, stiff spines along the margins. Fine hairs give the plant a greyish appearance. The massive main stem may be 10 cm wide at the base, and is branched in the upper part. Each stem shows a vertical row of broad, spiny wings (conspicuous ribbon-like leafy material), typically 2–3 cm wide, extending to the base of the flower head. The flowers are globe shaped, 2–6 cm in diameter, from dark pink to lavender, and are produced in the summer. The flower buds form first at the tip of the stem and later at the tip of the axillary branches. They appear singly or in groups of two or three on branch tips. The plants are androgynous, with both pistil and stamens, and sit above numerous, long, stiff, spine-tipped bracts, all pointing outwards, the lower ones wider apart and pointing downwards. After flowering, the ovary starts swelling and forms about 8,400 to 40,000 seeds per plant.

Habitat:

The plant prefers habitats with dry summers, such as the Mediterranean, growing best in sandy, sandy clay and calcareous soils which are rich in ammonium salts. It grows in ruderal places, as well as dry pastures and disturbed fields. It's preferred habitats are natural areas, disturbed sites, roadsides, fields, and especially sites with fertile soils, agricultural areas, range/grasslands, riparian zones, scrub/shrublands and water courses. Found in a Mediterranean Shrubland.

Notes:

his thistle reproduces only by seeds. Most seeds germinate in autumn after the first rains, but some seeds can germinate year round under favourable moisture and temperature conditions. Seeds that germinate in late autumn become biennials. But when they germinate earlier, they can behave as annuals. Buried seed can remain viable in the soil seed bank for at least seven years and possibly for up to twenty years or more. Yearly seed production and seed dormancy are highly variable depending on environmental conditions. The slender and smooth achenes are about 3 mm long and are brown with gray markings. They are tipped with a pappus of slender bristles. Mainly locally dispersed by wind, or more widely by humans, birds, wildlife, livestock or streams, the seeds are sensitive to light and only germinate when close to the surface. Seedlings will emerge from soil depths up to 4.5 cm, with 0.5 cm being optimal. The leaves of this thistle provide food for the caterpillars of some Lepidoptera, such as the Thistle Ermine (Myelois circumvoluta).

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Monda, Andalucía, Spain

Lat: 36.63, Long: -4.83

Spotted on May 10, 2010
Submitted on May 10, 2010

Spotted for mission

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