Narrow-leaved cudweed produces tiny flowers (4) and has small, narrow, silvery-grey to green leaves. The seeds are known as achenes, which are single seeded fruits that separate from the plant in one piece (5). Two types of achene are produced, the first type is shed in the bracts, and the second type is blown away in the wind (4). The common name of the cudweeds arises from the practice dating from the 1600s of placing these plants in the mouth of cows that had 'lost their cud' (6).
Narrow-leaved cudweed tends to occur as a summer annual in the UK, but seeds can generally germinate at any time of the year, so it may occasionally occur as a winter annual. The flowers are thought to self-pollinate, and there have been no records of insects visiting the flowers (4). A seed bank can lie dormant until conditions become suitable for the plant to germinate (3). Although thought to be an introduced species in Britain for many years, recent work suggests that it is actually a native species (4).
In the UK this species reaches the northern extreme of its range (4). It is restricted to the south-east of England and Sark in the Channel Islands, and has always been rare (3). During the last 100 years this plant has suffered a serious decline (4), and was thought to be extinct on mainland Britain by 1955 (4). Elsewhere it occurs mainly in south and west Europe and North Africa (4) and is threatened in Eastern Europe (3).
Narrow-leaved cudweed has declined because of changes in agriculture, and the rabbit population crash after the introduction of myxomatosis, which led to a decrease in the level of disturbance (3). At one Essex site the cessation of military activity after the war is thought to have resulted in the loss of the species following scrub invasion and dense growth of grasses (4). Rubbish dumping and scrub invasion are currently the main threats on Sark (4).
In 1994 it was discovered that there was a source of native narrow-leaved cudweed in cultivation. A re-introduction programme was established by Plantlife, the wild plant conservation charity, and by 1998 the species had become established at the last known British site (4). A Biodiversity Action Plan has been formulated by Plantlife, and seed has been collected for the Millennium Seed Bank at Royal Botanic Gardens, Kew (4).
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