All broomrapes are said to resemble 'withered orchids' (4); they are parasitic, and lack the green pigment chlorophyll. Thistle broomrape is a stocky plant, and has yellow stems often with a purple tinge. The leaves are scale-like and the flowers, which have two lips, are yellowish-white or purple in colour (2).
Thistle broomrape is a parasite of the roots of thistle, particularly of creeping thistle, Cirsium arvense and seems to prefer small, young host plants (3). It is a perennial species (lives for more than one year) but can also occur as an annual or a biennial, depending on the situation (3). It first appears in July and produces many small seeds, which have good powers of dispersal and seem able to remain dormant for a number of years (3).
In the UK, this species occurs only in Yorkshire in about 70 populations (3). It also occurs throughout much of Europe reaching into North Africa and western Asia. The status of the species in Britain is not clear; some authorities believe that it is a separate species to the form that occurs on the continent, and is therefore endemic to our shores (3).
Thistle broomrape receives full protection under the Wildlife and Countryside Act 1981, it is therefore illegal to cut, uproot, destroy or sell this species. As the species cannot survive in dense vegetation, disturbing the soil and opening up the sward is beneficial, and has increased the population at a few sites (3).
A plant that lives for two years and typically flowers only in the second year.
A group of green pigments found in photosynthetic organisms (photosynthesis is a metabolic process characteristic of plants in which carbon dioxide is reduced, using energy absorbed by the green pigment chlorophyll. Organic compounds are made and oxygen is given off as a by-product).
A species or taxonomic group that is only found in one particular country or geographic area.
In plants, petal or petals that form a lobe.
An organism that derives its food from, and lives in or on, another living organism at the host's expense.
Plants that live for at least three seasons; after an initial period they produce flowers once a year.
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