Growing garlic in Western Australia

General information

In the past 20 years the consumption of garlic in Australia has increased. It is used mainly as a flavouring for other foods and as a health food. Garlic contains alliin which is converted to allicin, a natural antibiotic compound, when garlic is cut or crushed. Various health claims including cardiovascular health have been made relating to allicin.

Garlic plants grow to 40–60cm high. The leaves are flat with a slight 'v' shape. The mature garlic bulb consists of modified storage leaves that contain six to 30 segments or cloves, held together by outer skins.

White, pink and purple-skinned varieties are available. Plants produce only a few flowers which are sterile and do not produce seed. Cloves are used as planting material.

New producers are advised to grow only a small area in the first year to gain an understanding of the crop before expanding. It may take several years to obtain an economic return. Garlic has a high value compared to many vegetables because of the high labour requirement for production and preparation for market. The high cost of planting material also contributes to the cost of production for new growers.

Industry

Garlic is imported into Australia throughout the year, but mainly from May to November. The chief source of imports is China, which produces about 75% of the world's garlic and in 2010/11 supplied 75% of Australia’s total imports of 10 650 tonnes.

Although Chinese bulbs are only of moderate quality, they are in demand because of low price. Garlic is also imported out-of-season from Mexico, Argentina, USA, Spain and Chile.

The main areas of Australian garlic production are South Australia, Victoria and New South Wales. A significant amount is processed. Promotion and health benefits have increased consumer interest in buying Australian garlic.

Consignments of garlic to Market City, Canning Vale, Western Australia from all sources increased from 415 tonnes in 1998 to 2 274 tonnes in 2010. With storage, locally produced Western Australian garlic is available from November to May.

It is only produced in small quantities for several reasons including:

• 0.6 to 1.0 tonne of cloves is needed to plant each hectare. For a new grower, obtaining good supplies of the best varieties for planting may be difficult and expensive.
• Established growers must retain 15% of the crop for planting material.
• Garlic imports from all countries are allowed entry by the Australian Quarantine Inspection Service. Growers may find it difficult to compete with cheap imports.
• Growing garlic is labour intensive, particularly harvesting and trimming. It is a long-term crop, taking six to eight months from planting to harvest.
• Garlic is not high yielding. While marketable yields up to 20 tonnes per hectare are possible, good commercial yields are closer to 10t/ha and yields of less than 5t/ha are not unusual.
• There are few processing outlets in Western Australia for out of grade bulbs.

Climate and soils

The best quality garlic grows in temperate climates. For initiation of cloves, the plants need cool winters. For good bulbing, this should be followed by increasing hours of daylight in spring and mild temperatures. If temperatures are too high, bulbs may not form, or side-shooting may be pronounced in certain varieties. If temperatures are too low, garlic has fewer, larger cloves.

Rainfall during harvest may cause skin splitting and storage rots, which reduce yields and quality.

Garlic grows well and can be harvested easily on light, well-drained, sandy soils. Waterlogged or heavy clay soils can restrict the roots, causing poor quality misshapen bulbs. The most suitable soils have a pH of 6 to 7 (measured in water) or 5.3 to 6.3 (measured in CaCl₂)

There should be a period of at least three years between successive crops of plants in the onion sub-family, to prevent a build-up of soil-borne diseases.

Varieties

There is often confusion on the names of the numerous garlic varieties sold on Australian markets because the varieties are often renamed with local names. Garlic can be grouped into soft-necked and hard-necked varieties. DNA studies have revealed that all garlic varieties are closely related to only 10 distinct varieties. Garlic is thought to have evolved in central Asia around Kazakhstan or Western China.

Soft-necked varieties

The soft-necked varieties generally produce larger bulbs and higher yields than hard-necked varieties. Side-shoots may break through the outer skins and produce unmarketable bulbs. This can occur in high temperatures and when too much nitrogen has been applied. Planting too early may also increase side-shooting. Varieties differ in their susceptibility to side-shooting.

• California Early is a medium to late-maturing variety with white skin and 16 large cloves per bulb; selections include Virginia, Murray Bridge and Dry Veg.
• California Late is a small, white, late-maturing variety. It has the best storage.
• Italian White 1 is a medium to large, white-cream variety with 22 cloves per bulb. It stores well.
• Italian White 2 (St George) is a medium to large, white-pearl variety with about 10 cloves per bulb. It stores well.
• Printanor is becoming more popular and is a leading variety in France and New Zealand. It is medium to large, white, with about 15 to 20 cloves per bulb. It stores well and has a rich flavour.

Hard-necked varieties

Hard-necked varieties generally produce fewer and larger cloves per bulb than the soft-necked varieties. They may produce bulbils, which are small cloves formed in the stem or on top of the stem. These can be used as a source of planting material when bulking up a new variety.

• Glenlarge is an early large-cloved purple variety with 6 to 12 cloves and suitable for warmer areas.
• Italian Pink is the main variety grown in WA and is medium-sized with thin, pink-purple skin. It matures early and produces about 12 cloves per bulb. It stores well for five months.
• New Zealand Purple is medium-sized with strong, white to purple skin, producing about eight cloves per bulb. It is easy to clean.

Elephant garlic

Giant Russian or elephant garlic (Allium ampeloprasum) is related more closely to leeks and is not a true garlic. It has a mild flavour and splits readily. It has a very large solid bulb, with three sides and five cloves.

Planting and harvest times

Table 1 shows the main times for planting and harvesting for the Perth area. For the hard-necked varieties, bulb size increases as the growing period lengthens. However, planting in high temperatures may retard bulb formation and increase water requirements. With Italian Pink, crops planted before February may mature in September and need a shed for drying. Late plantings result in smaller bulbs.

Table 1 Main planting and harvest times for the Perth area

Planting

Obtaining planting material for garlic can be difficult as there are few growers in Western Australia. The potential grower should approach an existing grower willing to supply good bulbs.

Planting material from Western Australian growers can be purchased from the sale floors at Market City, Canning Vale, from spring to autumn.

Planting imported garlic is not permitted in Western Australia under quarantine regulations because of the risk of spreading introduced diseases. Anyhow, garlic imported from overseas is fumigated and will not grow well.

If importing planting material from interstate, then quarantine requirements need to be met involving plant material treatments and inspections. Importers of small consignments unsure of requirements may contact Quarantine WA on +61 (0)8 9334 1800 for information.

Store planting material as whole bulbs. Garlic can be hung in bunches in a ventilated shed over summer, but it is preferable to store at 10°C. In cool storage, temperatures must not be below 5°C or above 18°C. Just before planting, separate the bulbs into cloves by hand or using compressed air. A mechanical tyre-type cracker, converging flat belts or separator with rubber rollers of decreasing sizes can speed up clove separation.

The cloves can be sorted by hand or mechanically through rubber covered rollers or a drum grader. Grading assists mechanical planting, separates smaller cloves and allows the largest to be planted first.

Select cloves of the correct size and colour that are free of pests and diseases. Small cloves will produce smaller bulbs than larger cloves and can, depending on the variety, be discarded. When bulking up a variety it may be necessary to plant all cloves, including bulbils.

Plant by hand or machine. Use cloves that do not have green shoots. Orientation of cloves by machine is not important, provided that the cloves are not planted upside down. This will reduce yields and make digging difficult.

Types of planters

• Halls seeders have a drum with vanes that pick up the cloves.
• Trickle seeders use a belt passing under a hopper to feed the cloves out in a stream.
• Cup seeders collect the various sized cloves into cups of different sizes.
• Cloves are fed by hand from a hopper down a tube to a seeding wheel or tine which is slow but accurate.

Cloves larger than 5g are ideal for planting, but smaller ones weighing 2–5g can also be used. As a guide, the amount of cloves recommended for planting 1 hectare, based on 320 000 cloves per hectare (32 cloves per square metre) and a bulb size of 50g is:

• up to 2t/ha for a variety with eight cloves per bulb
• 1.3t/ha for a variety with 12 cloves per bulb
• 0.5-1.0t/ha for a variety with 20 cloves per bulb.

Plant garlic 2.5‑4cm deep in rows 25‑30cm apart. Within rows, plant 8‑10cm apart, to give a population of about 40 cloves/m². After allowing for tractor paths this layout uses 320 000 cloves per hectare. Increasing the clove density to 60/m² increases yields but reduces bulb size and increases cleaning time.

Irrigation

Garlic is shallow-rooted to about 40cm depth and in dry weather on sandy soils needs daily watering. On dry days, water the crop in the early morning and to replace 130% of daily evaporation using sprinkler irrigation. If evaporation exceeds 6mm, then irrigation should be split into two waterings, ideally one early morning and one early afternoon. Good watering is especially important from early bulbing until three weeks before harvest. Uneven watering will contribute to split skins.

The soil needs to be dry when the leaves start to die down and watering is decreased as the bulbs mature. With Italian White, irrigation can stop when the gaps between the cloves are first visible. The crop can be pulled three weeks later.

Fertiliser

Nutrient analyses of the soil and irrigation water before planting, plus one to two plant analyses of the youngest mature leaves during growth are recommended. This will provide information on nutrients that are deficient or toxic and allow adjustment to the fertiliser program. Some nutrients in the fertiliser programs suggested in this webpage may be deleted or reduced if it is obvious that sufficient quantities are present in irrigation water, soil, compost or fertilisers from previous cropping.

Using compost in the rotation or before planting at up to 50 cubic metres per hectare will be beneficial. It will supply nutrients, organic matter, and help retain moisture in the soil. Apply phosphorus, magnesium and trace elements to sandy soils before planting (see Table 2).

Table 2  Fertilisers and application rates for sandy soils before planting

Starting one week after planting, apply side dressings of nitrogen as urea (70kg/ha) each fortnight until the start of bulbing. Bulbing starts six to eight weeks before harvest when the base of the stem is 1.5 times the diameter of the main stem and small cloves can be seen internally in cross-section. Late applications of nitrogen will result in excessive side shoots.

Apply topdressings of muriate of potash (85kg/ha) with the fortnightly application of nitrogen until bulbing, with two applications of potash (without nitrogen) after bulbing.

On fertile soils, garlic can be grown with much lower applications of fertiliser.

On alkaline soils, extra trace elements may be necessary after planting and before bulbing. Zinc is the main trace element required and applied as zinc sulphate as a foliar spray at 4g/L. Symptoms of zinc deficiency in garlic include stunting of plants and yellowing of young (inner) leaves which develop burnt tips.

Manganese sulphate applied at 8g/L may also be needed. Manganese deficiency is seen as streaking of younger leaves and leaf twisting around the stem axis.

Do not apply excess fertiliser. Nitrogen, phosphorus and potassium are readily leached through sandy soils by rainfall and irrigation and can cause groundwater pollution in rivers and estuaries. Excess fertiliser will also result in side shoots in the garlic.

Weeds, pests and diseases

Garlic has a long growing period and does not compete well with weeds which can seriously affect yields. Ideally, garlic should be planted in areas with low weed burdens which means that weeds should be well managed in the area prior to planting garlic.

Weeds compete with garlic to reduce yield

The herbicide chlorthal-dimethyl (available under a range of trade names) is the only residual weedicide currently registered for use on garlic.

This post-planting herbicide controls many broad-leaved and grass weeds before they emerge but does not control some troublesome weeds such as fumitory, potato weed (Galinsoga parviflora), wild radish (Raphanus raphanistrum), clover and nutgrass. For current registrations and minor use permits go to the Australian Pesticides and Veterinary Medicines Authority website (apvma.gov.au). Young garlic may also be cultivated by machine between the rows.

Garlic attracts fewer pests and diseases than most vegetable crops.

The major pest is thrips, which are found beneath the leaves and between the leaf base and stem. Thrips are 0.5‑2mm long, mobile and feed by rasping. Small white patches appear on the leaves and the bulbs may shrivel. Other pests include red-legged earth mite, aphids, snails and nematodes. The most common disease is downy mildew (affecting the leaves). For current pesticide registrations and minor use permits go to the Australian Pesticides and Veterinary Medicines Authority website (apvma.gov.au).

Plants may also be damaged by several diseases on the leaves and bulbs in the field and the bulbs in storage particularly with high relative humidity. Check with the AVPMA for current registered chemical control measures and those chemicals covered by minor use permits.

Yields and quality of garlic plants are reduced by virus infections. It is believed that most garlic in Australia is affected by three types of viruses which may appear as a yellow streaking of the whole plant, or have no visual symptoms. In future, it may be possible to obtain virus-free planting material in Australia.

Harvest and postharvest

Maturity

Indications of garlic maturity are:

• The stems have not fallen down, but leaves have started to die back and are still slightly green.
• Bulbs are of good size.
• Cloves are seen easily from outside the bulb.
• In cross-section, the skin between the cloves becomes thin and well-developed rather than fleshy.
• Internal clove colour is creamy rather than white.
• The neck softens above the bulb.
• Bulbs develop in the neck or on top of hard-necked varieties.

Do not allow bulbs to over-mature in the field, as too many skins will be discarded and bulbs will discolour, open up and become sunburnt or rot.

Pull the bulbs by hand. Harvesting with an onion machine can cause excessive bruising. Some harvesting is now done with a modified carrot harvester. Undercutting with a back blade to ease pulling and reduce labour is most common.

If the plants are uniformly mature and well-cured, they can be topped and tailed at harvest. However if they are still green, most of the stem will need to be retained to allow the cloves to mature as the plant dries. Topping and tailing too early without sufficient curing can promote storage rots.

If the plants are to be lifted whole, place them top over tails (to prevent sunburn) in rows in the sun for up to two weeks if no rain is imminent. This produces white shiny bulbs, allows deeper stacking of plants on pallets in sheds and aids cleaning.

If it is necessary to store bulbs immediately after harvest while the plants are green, care must be taken not to stack them too deeply and cause rotting.

Just before marketing, top and tail with secateurs or knives. Clean the bulbs of all loose scales and roots and grade them for size. Cleaning aids include brushes to remove loose scales.

Continuous handling of garlic may cause skin dermatitis in some people.

Storage

If kept dry and well ventilated, garlic will keep well as whole bulbs at ambient temperatures for two to five months. They may shrink if kept too long.

Long-term storage at 0 to 1°C, at a relative humidity lower than 60 per cent will keep garlic in good condition for up to five months. It can rot if the relative humidity is too high and bulbs can sprout above 5°C.

Eriophyid mites can be a problem in storage, especially if the relative humidity is too high. These mites cause brown sunken spots on the cloves.

Marketing

Market garlic in 10kg cartons. Well-presented, large garlic attracts the best prices. Supplies from all sources are fairly evenly balanced throughout the year.

Grading will maximise returns. Voluntary grading standards for bulb diameter in Australia are: medium 35 to 45mm; large 45 to 55mm; extra large 55 to 65mm; jumbo 65 to 75mm; and super colossal, more than 75mm.

Organic garlic

There is potential to increase supplies of organic garlic for the domestic market and to develop export markets in Asia. The best prices are obtained for organic produce. However, this may have lower yields and smaller bulbs than conventionally-grown garlic.

Organic garlic is grown without synthetic fertilisers and pesticides and is best grown under the directions of an organic certifying organisation such as the National Association for Sustainable Agriculture, Australia or the Biological Farmers of Australia.

Garlic shoots

Some garlic is marketed on the domestic market from May to September as ‘fresh garlic shoots’ or ‘garlic leek’, of which the edible part is the stem. This should be 10 to 20cm long, with no sign of bulb swelling. Italian Pink is a good variety for this purpose. The Giant Russian or elephant garlic may also be used to supply ‘garlic leeks’ on the domestic market. Garlic shoots are washed, trimmed, cleaned and graded. They are used as a garnish, in stir-fries and soups.

Storage in oil

Storing garlic in oil is not recommended because of the risk of botulism. Botulism is a potentially fatal food poisoning caused by a toxin produced by the bacteria Clostridium botulinum in the absence of oxygen. Commercial preparations of garlic in oil contain acidifying agents that prevent the growth of the Clostridium bacteria. Freezing or pickling in vinegar is a safer alternative for preserving garlic in the home.

Acknowledgement

This information is based on a DAFWA Farmnote prepared by John Burt.

Further information

AGIA (Australian Garlic Industry Association)
Email: info@garlicaustralia.asn.au
Web: www.garlicaustralia.asn.au

Perth Markets Ltd (PML), Market City website for production and prices at www.perthmarket.com.au