Monday, December 26, 2016

Hieracium pilosella

Hieracium pilosella (syn. Pilosella officinarum), known as mouse-ear hawkweed, is a yellow-flowered species of flowering plant in the daisy family Asteraceae, native to Europe and northern Asia. It produces single, lemon-coloured inflorescences. It is an allelopathic plant. Like most hawkweed species, it is highly variable and is a member of a species complex of several dozens of subspecies and hundreds of varieties and forms.


It is a hispid (hairy) perennial plant, with a basal rosette of leaves. The whole plant, with the exception of the flower parts, is covered in glandular hairs, usually whitish, sometimes reddish on the stem. The rosette leaves are entire, acute to blunt, and range from 1–12 centimetres (0.39–4.72 in) long and 0.5–2 centimetres (0.20–0.79 in) broad. Their underside is tomentose (covered with hair). The flowering stem (scape) is generally between 5–50 centimetres (2.0–19.7 in) tall, and sprouts from the centre of the basal rosette. The flowerheads are borne singly on the scape and are a pale lemon-yellow colour, with the outermost ligules having a reddish underside. It flowers from May until August and the flowers are visited by various groups of insects, especially flies.


The plant favours dry, sunny areas. It grows well on sandy and similarly less fertile ground types. It produces stolons are which generate a new rosette at their extremity, each rosette has the possibility of developing into a new clone forming dense mats in open space. It also propagates by seeds.

It is a known allelopathic plant, whose roots secrete several substances inhibiting root growth, including its own. It can be controlled through rotation with clover and grasses where possible.

Recent research claims that Hieracium pilosella exhibits an atavism by the reemergence of sexual reproduction.

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