Extract from MAFF Advisory Leaflet 853 (published 1983)
Garlic, unlike bulb onions, has a 'cold requirement' and it is necessary to expose dormant cloves or young plants to temperatures of 0 - 10°C for 1 - 2 months. This normally occurs in the storage sheds or after the crop has been planted in the field, from September until December. Maximum vegetative growth occurs at temperatures around 16°C in 'short days'.
Garlic then forms new bulbs in response to the lengthening days of June. Bulbing and maturity are considerably hastened if temperatures are high (above 20°C). As drying is very important, it is necessary to harvest in the summer. Also, leaving the bulbs in the soil too long increases the risk of skin discoloration.
Varieties and Stocks
Obtaining good stock can be difficult and contacts in France may offer the best opportunity. Wherever possible some 'certification' that stock is not infected with stem and bulb nematode, or infected with white rot, should be obtained.
Where multiplication is carried out at home, bulbs need to be heat dried for two days after separation. This allows the base plants to shrink and the wrapper leaves to become brittle, allowing easy splitting. Separation is mainly done by hand, immediately prior to planting.
Two categories of French varieties exist:
- Autumn varieties of short dormancy which do not keep well and have to be planted well before the winter solstice (21 December). Leaves are broad (30 mm) and the cloves generally large. They store for 4 - 5 months in crates in a well ventilated building.
- Messidrome or Blanc de la Drome; very large, regular bulbs, ivory coloured.
- Thermidrome; very large, regular bulbs, pink or pink marked. Hardier, but slightly less
- productive than Messidrome.
- The second category have log dormancy and can be planted before or after the winter solstice. Leaves are narrow (20 - 50 mm) and cloves generally small. They will store for 7 - 8 months. All French varieties of this category are infected with Garlic Mosaic virus.
- Rose de Lautrec: Plant produces a floral scape which must be removed to allow bulbs to
- grow. Light pink cloves, regularly arranged around the centre.
- Fructidor: Late, pink/white bulbs.
- Brignole BR4 (INRA): Preferred in S. France to Fructidor.
- Revigo 24 (INRA)
- Rose d'Italie R 024: Late and often gives the heavier yield and best presentation.
American, Egyptian, Chinese, Japanese, Turkish and Mexican varieties also occur in the world market.