Galium aparine (cleavers)
Cleavers is a botanical hitchhiker with a medicinal past, present and future.
About this species
This climber is well known by children for its 'stickiness', owing to its covering of hooked hairs. There is a rather cruel Scottish children's game involving this plant. The trick is to persuade somebody to allow a piece of it to be put in their mouth - then pull it out fast. The hooks being rather sharp, the game is called 'bleedy tongues'! Galium aparine is also well known by herbalists for its medicinal properties.
Geography & Distribution
Galium aparine is naturally widespread throughout Europe, North America and some parts of Asia, and occurs as far north as Alaska and Greenland. It has been introduced as far south as Australia, New Zealand, and the sub-Antarctic Islands. It can be a troublesome weed of cereal crops (especially in Europe and North America). Heavy infestation can cause significant yield losses, and its seeds can be difficult to separate mechanically from those of crops such as oilseed rape (canola). It is found throughout the British Isles (except in some places in the far north) and appears to be increasing in abundance in recent years despite the use of species-specific agricultural herbicides. Galium aparine can be found growing naturally on scree slopes and shingle banks.
This species is a straggling climber, growing up to 3 m long, with slender 4-angled stems. Its narrow leaves can reach 7 cm long and are arranged in groups (whorls) of 6-8 (rarely 4) around the stem. The whole plant is covered in minute hooked hairs, and can cling to skin, fur and clothing. The flowers are tiny, white, 4-petalled tubes, developing into small round fruits, often borne in clusters of two or three. These fruits are also covered in hooked hairs which catch in the fur of passing animals or the clothes of humans. This is an efficient distribution mechanism that has contributed to the plant’s wide geographical range.
The whole plant is edible, though not particularly tasty, and in China, for example, it is eaten as a vegetable. Its seeds can be roasted to prepare a sort of coffee substitute. It is also reputed to have a number of medicinal properties, having been used in traditional medicine (usually as an infusion) to treat kidney problems, skin disorders and high blood pressure among other ailments. Archaeological evidence suggests that it may have been used in this way for hundreds, if not thousands, of years. Cleavers is still used by medical herbalists today, although scientific evidence regarding its effectiveness is still lacking.
Britain's wild harvest
Kew’s Sustainable Uses of Plants Group undertook a survey of commercial uses of wild and traditionally managed plants in England and Scotland for the Countryside Agency, English Nature and Scottish Natural Heritage to determine the economic role of wild plants and to assist in their sustainable use. Despite the revival of interest in herbal remedies in UK most plant material used in herbal products is imported. However, there are exceptions. In Norfolk, for example, cleavers is gathered from hedgerows and used in herbal products.
Millennium Seed Bank: Seed storage
Kew's Millennium Seed Bank partnership aims to save plant life world wide, focusing on plants under threat and those of most use in the future. Seeds are dried, packaged and stored at a sub-zero temperature in our seed bank vault.
Number of seed collections stored in the Millennium Seed Bank: 8
Seed storage behaviour: Orthodox (the seeds of this plant survive drying without significant reduction in their viability, and are therefore amenable to long-term frozen storage, such as at the MSB)
Germination testing: Successful
Composition values: Oil content 3.1%, Protein 12.7%
Galium aparine (Image: William Milliken)
This weedy species is an annual that can be grown in temperate regions, in parts of the garden managed for wildlife, as either a summer or winter annual (or occasionally as a biennial). The seed is thought to be viable for around 2-6 years unless frozen. Seeds should be sown in moist soil, preferably a rich loam, with above-average fertility and pH of 5.5-8.0. Seeds must be buried to germinate, ideally at a depth of 2-10 mm. Seeds that have passed through the gut of a herbivore are thought to have a higher germination rate. Development is rapid with flowers appearing as soon as eight weeks after germination. Ripe seeds develop from summer through to autumn, depending on the region in which plants are grown. Supports such as pea sticks can be provided, as this plant likes to scramble. Plants will die down after the fruits are released at which point seeds must be collected for next year’s plants.
Note that this plant can be invasive. In some parts of the world it is a serious weed of crops and native vegetation, where it can out-compete indigenous species. For this reason, if cultivating cleavers, care should be taken to prevent its spread into farmland or sensitive areas of conservation importance.
Download the Great Plant Hunt Identikit for Galium aparine here
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