An introductive definition

Morphological description

Crop aspects

Phytopathology

Taxonomical definition

Nutritional value



An introductive definition

Garlic (Allium sativum) is a perennial plant in the family Alliaceae and genus Allium, closely related to the onion, shallot, and leek. It does not grow in the wild, and is thought to have arisen in cultivation, probably descended from the species Allium longicuspis, which grows wild in south-western Asia.

The portion of the plant most often consumed is an underground storage structure called head. A head of garlic is composed of a dozen or more discrete cloves, each of which is a botanical bulb, an underground structure comprised of thickened leaf bases.

Each garlic clove may often be composed of just one leaf base, unlike onions, which almost always have multiple layers. The above-ground portions of the garlic plant are also sometimes consumed, particularly while immature and tender.

Like other members of the onion family, garlic actually creates the chemicals that give it its sharp flavour. Although people have come to enjoy the taste of garlic, these compounds are believed to have evolved as a defensive mechanism, deterring animals like birds, insects, and worms from eating the plant. 1

Back to the index



Morphological description

Garlic flower cluster

A garlic head is generally four to eight centimeters in diameter, white to pinkish or purple, and is composed of numerous (8 - 25) discrete bulbs. The foliage comprises a central stem 25 - 100 cm tall, with flat or keeled (but not tubular) leaves 30 - 60 cm long and 2 - 3 cm broad. The flowers are produced in a small cluster at the top of the stem, often together with several bulblets, and surrounded by a papery basal spathe; each flower is white, pink or purple, with six tepals 3 - 5 millimetres long. The flowers are commonly abortive and rarely produce any seeds.

The garlic plant has long, narrow, flat, obscurely keeled leaves. The head (compound bulb) has a flaky, mostly white outer layers of skin like that of an onion. Inside are 8-25 cloves, or smaller bulbs. From these, new bulbs can be procured by planting out in late winter or early spring. The percentage composition of the bulbs is given as water 84.09 %, organic matter 13.38 %, and inorganic matter 1.53 % - that of the leaves being water 87.14 %, organic matter 11.27 % and inorganic matter 1.59 %. 2

Back to the index



Crop aspects

Soil Preparation Garlic will tolerate a wide range of soils but prefers a free-draining loam high in organic matter. If well-rotted manure is not available then a generous application of a general purpose fertiliser should be raked in immediately prior to planting. This should be followed by two further applications of nitrogen (as ammonium nitrate, ammonium sulphate, urea, etc.) in April and May, applied between the rows at a rate equivalent to 15-20 grams of nitrogen per square metre.

Planting Ideally, garlic should be planted between mid-September through to early November although planting can be left until spring if you are prepared to accept a lower yield. Separate the bulbs into individual cloves just prior to planting and space them at 10 cm in rows about 30 cm apart. Plant them base down so that there is about 50 - 70 mm soil over the top of the cloves and lightly firm the soil with the back of a spade. In milder districts no winter protection is necessary but those areas exposed to heavy frosts will benefit from a winter mulch of straw or fleece. If you do plant in spring remember that garlic requires a month or so of low temperatures in order to bulb up properly so store bulbs in a frost-free shed.

Irrigation During the growing season it is important that the plants have adequate moisture. From March onwards the soil should be checked regularly and watered as necessary. Always water in the morning to allow foliage to dry out before nightfall in order to reduce the likelihood of disease. If drought occurs during the bulbing period yields will suffer and remember to stop watering once bulbing has finished to prevent bulb rot.

Cultivation All hardneck and some softneck plants will produce a false seedstalk topped by an umbel containing numerous small bulbils. Although opinions differ about seedstalk removal, it is generally believed that bulb yields are higher from plants that have had seedstalks removed than from those left intact. Stalks should not be removed too soon, it is best to wait until the seedhead begins to coil before cutting it off cleanly with a knife as low down the plant as possible. Of course plants can be left intact and bulbils left to form. The bulbils look and taste just like miniature garlic cloves and if planted will germinate and form a `round' or single clove bulb in their first year. The following year these 'rounds' will develop into normal, segmented bulbs which can be harvested in the normal way. Some varieties have a tendency to produce bulbils in the neck of the flower stalk but the bulbils will still mature and can be used in the same way. Simply plant whatever you have in a dense seedbed and keep well watered. 3

Back to the index



Phytopathology

Diseases Botrytis Neck Rot, Blue Mould (Penicillium) and Fusarium Base Rot can cause significant losses in both growing and stored bulbs. Land infected by White Rot - a potentially devastating disease of garlic - can take over twenty years to clear, so a five year cycle of crop rotation with unrelated vegetables such as beans, peas, carrots, cabbage or potatoes should, wherever possible, be used. Avoid rotating with related crops such as onions, shallots or leeks. Take care with watering - avoid over-watering particularly late in the day and stop watering once bulbing has finished. Leaf Rust is another disease, typically associated with leeks, that can cause significant losses in garlic. Rust infection is promoted by low light and high moisture levels so avoid shade and maintain close attention to watering. Infected plants should be treated immediately either by removal and burning or by spraying with an appropriate fungicide.

Pests All pests that attack onions will affect garlic crops. The most significant pest is likely to be nematodes (eelworms) which attack the roots and bulbs. Bulbs should be inspected before planting to ensure cloves are nematode-free and if possible dusted with nematicidal powder immediately prior to planting. Thrips and onion maggot are two other potentially serious pests although both can be effectively controlled by the use of insecticides and/or crop rotation. 4

Back to the index

Taxonomical definition
Kingdom Plantae
Division Magnoliophyta
Class Liliopsida
Order Asparagales
Family Alliaceae
Subfamily Allioideae
Tribe Allieae
Genus Allium
Species A. sativum
Nutritional value for 100 g of edible parts 5
Energy 410,7 kcal (1,7 kJ)
Carbohydrates 33 g
Fat 0,34 g
Protein 9,26 g
Water 66,32 g
Vitamine B6 1.2 mg
Iron 5,29 mg
Calcium 36,3 mg
Phosphorus 600,9 mg

Back to the index