'Clover' ('''Trifolium''') is a
genus of about 300
species of
plants in the pea family
Fabaceae. The genus has a
cosmopolitan distribution; the highest diversity is found in the temperate
Northern Hemisphere, but many species also occur in
South America and
Africa, including at high altitudes on mountains in the tropics.
They are small
annual,
biennial, or short-lived
perennial herbaceous plants. The leaves are trifoliate (rarely 5- or 7-foliate), with stipules adnate to the leaf-stalk, and heads or dense spikes of small red, purple, white, or yellow flowers; the small, few-seeded pods are enclosed in the
calyx.
Other closely related genera often called clovers include ''
Melilotus'' (
sweet clover) and ''
Medicago'' (
alfalfa or 'calvary clover'). The "
shamrock" of popular iconography is sometimes considered to be young clover.
The scientific name derives from the
Latin ''tres'', "three", and ''folium'', "leaf", so called from the characteristic form of the leaf, which has three
leaflets (trifoliate); hence the popular name '
trefoil'. Clovers are used as food plants by the
larvae of some
Lepidoptera species; see
list of Lepidoptera which feed on Clovers.
Red clover (''Trifolium pratense'')
;Selected species
Cultivation
White Clover flower-head and leaves
Several species are extensively cultivated as fodder-plants. The most widely cultivated clovers are
White clover ''Trifolium repens'' and
Red clover ''Trifolium pratense''. Clover, either sown alone or in mixture with
ryegrass, has for a long time formed a staple crop for soiling, for several reasons; it grows freely, shooting up again after repeated mowings; it produces an abundant crop; it is palatable to and nutritious for
livestock; it grows in a great range of
soils and
climates; and it is appropriate either for pasturage or green composting.
In many areas, particularly on acidic soils, clover is short-lived due a combination of insect pests, diseases and nutrient balance; this is known as "clover-sickness". When
crop rotations are managed so that clover does not recur at shorter intervals than eight years, it grows with much of its pristine vigour.
"Clover sickness" in more recent times may also be linked to
pollinator decline; clovers are most efficiently pollinated by
bumblebees, which have declined as a result of agricultural intensification.
Honeybees can also pollinate clover, and
beekeepers are often in heavy demand from farmers with clover pastures. Farmers enjoy the benefits of increased reseeding that occurs with increased bee activity, which means that future clover yields remain abundant. Beekeepers benefit from the clover bloom as clover is one of the main
nectar sources for honeybees.
Red Clover flowers
''T. repens'', White or Dutch clover, is a perennial abundant in meadows and good pastures. The flowers are white or pinkish, becoming brown and deflexed as the corolla fades. ''T. hybridum'', Alsike or Swedish clover, is a perennial which was introduced early in the
19th century and has now become naturalized in Britain. The flowers are white or rosy, and resemble those of the last species. ''T. medium'', meadow or zigzag clover, a perennial with straggling flexuous stems and rose-purple flowers, is of little agricultural value.
White Clover flower
Other British species are: ''T. arvense'', Hare's-foot trefoil; found in fields and dry pastures, a soft hairy plant with minute white or pale pink flowers and feathery sepals; ''T. fragiferum'', Strawberry clover, with densely-flowered, globose, rose-purple heads and swollen calyxes; ''T. procumbens'', Hop trefoil, on dry pastures and roadsides, the heads of pale yellow flowers suggesting miniature hops; and the somewhat similar ''T. minus'', common in pastures and roadsides, with smaller heads and small yellow flowers turning dark brown. The last named is often called
Shamrock.
Clovers are a valuable survival food, as they are high in
protein, widespread, and abundant. They are not easy to digest raw, but this can be easily fixed by boiling for 5-10 minutes. Dried flowerheads and seedpods can also be ground up into a nutritious flour and mixed with other foods. Dried flowerheads can also be steeped in hot water for a healthy, tasty tea.
Symbolism and mythology
A four-leaf clover
, the traditional
Irish symbol coined by
Saint Patrick for the
Holy Trinity, is commonly associated with clover, though also sometimes with ''
Oxalis'' species, which also have trifoliate leaves.
Clovers occasionally have leaves with four leaflets, instead of the usual three. These
four-leaf clovers, like other rarities, are considered lucky.
A common
idiom is "to be in clover", meaning to be living a carefree life of ease, comfort, or prosperity.
The
cloverleaf interchange is named for the resemblance to the leaves of a (four-leafed) clover when viewed from the air.
References
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