Garlic (Allium sativum) is a vegetable in the family Alliaceae, and is closely related to onions, shallots, leeks and chives. Garlic is primarily grown for its bulbs, which are used in cooking and for medicinal purposes.
Glenlarge and Southern Glen are superior large-cloved varieties developed at Gatton Research Station. They are the highest yielding and have a light purpling of the outer skin. Southern Glen matures approximately one to two weeks before Glenlarge. The old medium and small purple varieties (probably of Taiwanese origin) are now rarely grown commercially because of their small clove size. Apart from South African White, which tends to produce a high percentage of small cloves, most other imported and southern strains have failed to produce bulbs. Giant Russian garlic, which is really a member of the leek family, is grown but the market potential appears to be limited.
Garlic can be grown in a range of soils, but prefers sandy to clay loams that are rich in organic matter and reasonably well-drained. As with onions, there are problems with a soil pH of over 8.0.
Establishing and maintaining garlic crops
Garlic is vegetatively propagated using cloves, which are the small bulbs or sections broken out of a complete garlic bulb. These are obtainable from growers. Larger bulbs and larger cloves provide the best planting material. It is important not to plant bulbs from soils infected with the disease white rot.
The amount of planting material required is 400 kg/ha to 600 kg/ha.
Planting should be carried out from mid-March to early April in the Moreton region, as garlic requires a cool growing season. Later plantings result in a reduction in bulb size.
Garlic should planted in rows 45 cm to 60 cm apart, with 8 cm to 13 cm between plants, and no deeper than 5 cm. The broken cloves are planted by manually dropping them through a tube behind a cultivator, or by specially developed planting machines. The recommended plant density is 25 to 30 plants per square metre.
In fertile soils, usually only nitrogen is required at 30 kg/ha to 120 kg/ha. Alternatively, an NPK (nitrogen:phosphorus:potassium) mixture, such as 17:3:6, plus an early nitrogen side-dressing, may be applied.
In less-fertile soils, garlic benefits from an NPK mixture (either 17:3:6 or 15:4:11) at 300 kg/ha to 450 kg/ha, plus nitrogen side-dressings as required. The fertiliser is spun on in several applications before bulbing. Poorer, sandy soils require mixtures containing more phosphorus. Late applications of nitrogen should be avoided, as they can affect quality.
In the early stages, frequent light irrigations of about 15 to 20 mm are needed. Less-frequent and heavier irrigations can be applied for later growth - approximately 50 mm per fortnight. It is important to avoid stressing the crop, particularly during bulb development.
Harvesting and marketing garlic
Maturity in garlic is not as easily defined as it is in onions, where the tops go down. Some indicators of maturity in garlic include progressive yellowing of the leaves, death of the youngest leaves, and tops that can be easily bent over.
Harvesting and storage
Garlic is usually harvested (pulled up) by hand about five to six months after planting. Tops and roots are removed by dagging shears after a short drying period in the paddock, or for longer periods in sheds.
Yields range from 4 t/ha to 8 t/ha. Around a five- to ten-fold return on planting material weight can be expected under good crop-management conditions.
Garlic is sold in standard onion bags or small pre-packed quantities in mesh bags. More innovative packaging may improve the return to the grower.