Overview: A bulbous herb growing to about 60 cm tall.
Bulb: Rounded, composed of up to about 15 smaller bulblets known as cloves. Cloves and bulbs are covered by a whitish or pinkish tunic (papery coat).
Leaves: Four to twelve long, sword-shaped leaves attached to an underground stem.
Flowers: Borne in a dense, spherical cluster on a spike (flower stalk) up to 25 cm long. The young flower head is enclosed in a long-beaked pair of enclosing bracts, which become papery and split to reveal the flowers.
Individual flower stalks arise from a common point. Flowers are greenish-white or pinkish with six perianth segments (sepals and petals) about 3 mm long. Bulbils (asexual propagules), which resemble tiny cloves, are often interspersed among the flowers.
Fruits: Flowers usually abort before developing to a stage at which fertilisation could take place.
Seeds: Not usually produced in the wild but have been produced under laboratory conditions. With a black coat, similar to onion seeds, but approximately half the size.
Almost 10 million tons of garlic is produced each year. The world's largest producers include China, Korea, India, USA, Spain, Egypt and Turkey.
Garlic bulbs are sold fresh or processed to produce a dry powder or oil. Garlic is popular in French, Spanish, Portuguese and South Asian cuisine. The bulb is the most commonly used part but chopped leaves are sometimes also used.
Garlic is one of the most frequently used plants in many parts of India, Pakistan and Bangladesh, and there are many ways of using it. Garlic is used not only to flavour curries but can be used in drinks and savoury desserts.
To add a mild flavour to food the fresh cloves are cooked whole. If a stronger flavour is required, garlic cloves are crushed or ground and added to the dish. Garlic should not be cooked for too long as it can become bitter. Often garlic heads with small cloves have a stronger flavour than larger ones.
Oil is processed from garlic and used commercially as flavouring. It can be added to flavour otherwise bland vegetable oils.
Garlic is not popular with everyone. Members of certain religious groups in India, such as Jainism and Brahman Hinduism, are forbidden to eat onion-related plants like garlic. The reasons differ in each case. Jains consider use of garlic to be too damaging to the plant, while some Hindus consider garlic too stimulating.
Garlic is one of the oldest plants to be widely used as a medicine. In most corners of the world, it is regarded as an aphrodisiac. Its medical qualities have been recognised since ancient times and feature widely in traditional remedies.
The bulbs are the most frequently used part of the plant. In India they are prepared in several ways including extracting the juice or pulping the bulb to a paste. This has been taken to relieve problems such as coughs and fevers or applied externally to prevent greying of hair and to improve skin conditions such as eczema and scabies. It has even been applied to the noses of hysterical girls to calm them down!
Garlic bulbs from Madhya Pradesh (from Kew's Economic Botany Collection).
Warmed garlic juice or a mixture made with oil and boiled bulbs have been dropped into the ear to relieve earache and deafness. In Ayurvedic and Siddha medicine, garlic juice has been used to alleviate sinus problems. In Unani medicine, an extract is prepared from the dried bulb that is inhaled to promote abortion or taken to regulate menstruation. Unani physicians also use garlic to treat paralysis, forgetfulness, tremor, colic pains, internal ulcers and fevers.
Extracts of bulbs have been widely used in folk medicine. Whooping cough in children has been treated by administering a drink made with a hot water extract of the dried bulb mixed with honey or by wearing a necklace of bulbs. Hot water extracts are also taken to kill intestinal worms. In Pakistan, an extract is traditionally taken orally to settle the stomach, treat coughs and reduce fever.
Garlic bulbs have sometimes been combined with other plants to make medicines. Mixed with the leaves of the ivy gourd (Coccinia grandis) it is used as a treatment for rabies. An infusion of the entire plant has been combined with sugar and taken to treat fevers. Garlic has also been used in traditional Indian veterinary medicine to treat tetanus and inflammatory disorders of the lungs.
Garlic also features in traditional medicine in other parts of the world. In Nepal, East Asia and the Middle East it has been used to treat all manner of illnesses including fevers, diabetes, rheumatism, intestinal worms, colic, flatulence, dysentery, liver disorders, tuberculosis, facial paralysis, high blood pressure and bronchitis.
The medicinal properties of garlic are now scientifically recognised. It is widely available in different forms as over-the-counter supplements, particularly to treat blood conditions and as an anti-viral medicine.
Various sulphur-containing compounds occur in garlic. One such compound is called alliin. Crushing or chopping garlic may also promote enzyme reactions and allow other compounds to form. Studies show that these compounds may be effective in many ways including: pain relief; anti-worm, anti-bacterial, anti-fungal, anti-viral, antioxidant, and anti-cancer properties; lowering of blood glucose and blood pressure; and liver protection.
Other research shows that garlic may help lower cholesterol, prevent blood clots and spasms, act as an expectorant and alleviate swellings, sores and acne.
Garlic is sometimes deployed in gardens to deter pests. Some companies have taken its pest-repelling properties a step further by isolating its active compounds and marketing them in a spray-on formula.
Crate of Allium sativum 'Picardy Wight' harvested at Kew
Garlic is often grown among flowers or root vegetables as a companion plant, with the aim of protecting other plants from pests. In some small garden plots, rows of garlic are planted along the perimeter to act as a deterrent.
Garlic extracts have also been used as deterrents. In Europe these extracts are freeze-dried and marketed as garlic pellets, which are then dissolved in water and sprayed onto plants to deter aphids and caterpillars. A disadvantage of these extracts is that the active sulphurous compounds have a pungent smell that can mask the perfume of roses and other aromatic plants.