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.