Herb production: Fertilisation and pest control for garlic

Best known as a culinary herb, garlic is also renowned for its medicinal properties. These tips will help you achieve production success.

Garlic cultivars differ in taste, length of storage, colour, size, number of cloves per bulb and suitability for cooking.

The South African Department of Agriculture, Forestry and Fisheries (DAFF) guidelines on garlic production advises farmers to choose a cultivar suited to the climate of the growing area and for which there is a good market demand. It should also be tolerant of diseases and pests.

  • Garlic performs well in warm climates, but it can survive winter temperatures.
  • Most of the conditions for onion production also apply to garlic.
  • The suitable growth temperature ranges from 13˚C to 24˚C.
  • Long days and high temperatures during the growing season encourage bulb formation.
  • The herb prefers well-drained fertile soil.
  • If planting in heavy clay-type soil, add compost or well-rotted manure.
  • The optimum soil pH for garlic is between 6 and 7.
  • The area should be well-tilled before planting to provide a loose (friable) growing bed for bulb development.
  • Keep the soil evenly moist at all times to prevent the formation of irregularly shaped bulbs.
  • DAFF recommends spacing divided cloves 8 cm to 15 cm apart, with a row spacing of 30 cm to 40 cm.
  • Plant cloves about 50 mm deep on raised beds or flat ground.
  • Planting dates vary according to climatic conditions, but can take place from February to May.

Also read: How to cultivate garlic


  • Garlic is known as a heavy, or gross, feeder, but farmers are cautioned to apply fertiliser based on soil test results.
  • Compost will improve soil fertility and structure, but nitrogen can be applied through irrigation.
  • Indiscriminate application of nitrogen can cause foliar burn.
  • DAFF guidelines indicate that the preferred sources of nitrogen are calcium or ammonium nitrate.
  • Avoid urea as it can injure plants.
  • Commercial farmers use furrow, sprinkler or drip irrigation.
  • Garlic has a fairly shallow root system and is easily affected by water stress.
  • Irrigation frequency and quantity will depend on the weather and soil conditions.
  • More water is needed in dry, hot conditions.
  • Farmers should apply mulch to the soil to reduce moisture loss.
  • Dry soil conditions, particularly during bulbing, can reduce yields.
  • Devices such as neutron probes can accurately determine the frequency and rate of irrigation needed.
  • It’s best to irrigate in the morning or mid-afternoon.
  • DAFF explains that this allows enough time for plant foliage to dry.
  • As the crop matures, farmers can reduce irrigation.
  • This makes it easier to harvest and reduces deterioration and staining of the exterior bulb sheath leaves.

Also read:
How to test soil life and health
How to build soil fertility with organic fertiliser
Maintaining soil health – make your own compost


  • Garlic’s susceptible to many pests and diseases.
  • To avoid cutworm, keep the land free of weeds for at least 6 weeks before planting.
  • Ploughing in winter will expose cutworms to birds.
  • Farmers could also spray with registered chemicals.
  • Pink stalk borer can be kept away by practising weed control and removing host plants near garlic fields.
  • Avoid brown rust by not planting too early.
  • White bulb rot can be controlled through crop rotation.
  • Pink root is a fungal disease spread through bulbs, so don’t propagate garlic with bulbs from infected fields.
  • Pink root-resistant cultivars are also available.
  • Neck rot, a parasite that enters the plants through wounds, isn’t common, but it can be prevented through using cultivation and harvesting practices that don’t damage plants.

Also read: Your library for herb production

  • This article was written by Wilma den Hartigh and first appeared in Farming SA.

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