garlic

Herb production: How to cultivate garlic

Apart from being used as a cure for several ailments, garlic is a great culinary herb. Here are some useful production guidelines.

Garlic (which belongs to the same family as onions, namely Alliacea) originated in the temperate to warm temperature zones of the northern hemisphere. Today, a number of cultivars are grown in different parts of the world.

The bulb formation of garlic is regulated by daylight hours and cultivars have adapted to different regions based on their latitude. Growers must ensure that they grow an adapted cultivar for a specific area. This is important if one wants to import plant material or use unknown cultivars.

This plant has been used as a cure for several ailments, including the treatment of high blood pressure and as an anti-inflammatory product, and it has also found great support as a culinary herb.

SELECTING THE RIGHT CULTIVAR

Try several lines, including the standard one for your production area. Test them for at least two, but preferably three seasons. Keep the lines separate throughout these three seasons.

Keep records of climate and plant response. If more than one line performed well, choose the one that proved most consistent over three years.

CLIMATIC REQUIREMENTS

Garlic is a cool weather crop and tolerates frost conditions. The optimum monthly temperature lies between 13°C and 24ºC, with the optimum maximum at 29ºC and the optimum minimum at 7ºC. Its growth rate is reduced when temperatures exceed 32ºC.

Studies have shown that bulb formation is better at a day length of 12 hours than at eight or 16 hours. Longer days and increasing temperatures during spring enhance growth and bulb development. Garlic must grow in full sun and sprouts rapidly at 5 ºC to 10ºC.

DEVELOPMENT STAGES

  • Sprouting: 10 to 20 days after planting, additional roots form and leaves emerge.
  • Shoot growth: From the end of sprouting until 140 days after planting, maximum leaf growth.
  • Bulb growth: Induction (90 days after planting), initiation (120 days after planting), bulb filling (140 days after planting).
  • Maturation: Leaf senescence.

SOIL REQUIREMENTS

  • Do not consider garlic production in soil with a pH lower than 6 or higher than 8. Avoid soils that tend to form a hard crust, because growth and bulb development can be impaired.
  • Do not plant garlic in soil where white bulb-rot occurred previously.

PLANTING TIMES

Planting in cool areas is done earlier than in warm areas, to ensure stronger plants before frost. Plants must be relatively strong when the first frost occurs so as to have a good yield. The Egyptian White cultivar can be planted earlier than the Small Pink.

  • Summer rainfall areas: February to March for common garlic.
  • Mid-March to mid-April for elephant garlic.

SPACING

Spacing is a very important aspect, because the closer the spacing, the higher the yields of smaller bulbs. Wider spacing produces bigger bulbs.

Spacing depends on the following factors:

  • Size of cloves.
  • Required bulb size.
  • Soil fertility.
  • Space required for weed control and implements available, etc.
  • Spacing of up to 65 plants per m² can be used, but the general recommendation is 35 plants/m² to 40 plants/m².
  • Spacing of 30 cm to 45 cm between rows and 6 cm to 7 cm between plants is recommended for large and medium cloves.

FERTILISATION

At the beginning of the season fertilisers are important to favour development of a good leaf canopy. The leaf canopy aims to promote translocation of reserves to the bulbs to develop strong tissue structure.

Each grower strives to obtain the best yield and storage ability. Fertilisation can assist to achieve the best quality. The most important elements are nitrogen, potassium and calcium.

No single recommendation can be made because of the variation in soil in different production areas. Please consult your fertiliser company or an extension officer in your area.

IRRIGATION

The most critical stage for irrigation is during bulb formation. Irrigation is one of the most important aspects and goes hand-in-hand with fertilisation of a crop to ensure a successful harvest (400 mm to 500 mm water per season is needed to grow a good garlic crop). In summer up to 30mm per week may be needed.

Keep the top layer of the soil moist at all times until plants have been established. Garlic roots may grow up to 900 mm deep, but most roots are confined to the top 200 mm to 300 mm of the soil.

A general rule is to irrigate garlic at least once a week. Stop irrigation 2 to 3 weeks before harvest.

YIELDS

Yields of 6 t/ha to 10 t/ha can be expected for common garlic and at least 10 t/ha to 15 t/ha for elephant garlic. Obviously, the yield is directly linked to soil fertility, weed control, size of the seed clove, plant population, planting date, irrigation, nitrogen application and storage conditions of planting material.

HARVESTING

  • Plants change colour at the end of the season.
  • Leaf tips start to dry out, especially the youngest leaves.
  • Plant necks become soft.
  • Plants start to fall over.
  • Cloves fill out the skins and do not shrink within 24 hours after cutting.
  • Dry the bulbs after harvesting to prevent post-harvest rotting.
  • The simplest way to dry garlic is in the field in wind rows, or stacks, for at least 5 to 7 days.
  • Good ventilation, out of sun and low humidity, are important when drying.
  • Clean the bulbs after drying and cut off the roots and leaves.
  • Don’t pull leaves off; rather use shears.

 

  • This article was written by Erika van den Heever at the Agricultural Research Council in South Africa and first appeared in Farming SA.

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