Garlic, Allium sativum L., is a member of a very large genus (over 500 species) of cultivated plants which includes onions, leeks, shallots and chives as well as other wild and ornamental species. The cultivated forms of garlic are thought to have descended from the wild species A. longicuspis, A. tuncelianum and perhaps A. macrochaetum and to have originated in the mountainous regions of Afghanistan, Uzbekistan and Tajikistan - typically arid areas with minimal rainfall and long, hot days. Wild Allium species still found in the region are weakly competitive, typically growing as patches of small populations on rocky, open sites and having long growing periods, taking between three and ten years to reach maturity.

Early travellers to the region were introduced to the remarkable curative, antiseptic and culinary properties of wild garlic and as they took bulbs with them on their journeys, so the plant became more widely distributed and cultivated outside of its native region. Over the past ten thousand years garlic has been subjected to intense domestic selection under a wide range of growing conditions and this has led to the creation of many hundreds, if not thousands, of clones.

There have been many attempts at classification but today it is widely accepted that cultivated garlic divides into four distinct groups - the ophioscorodon group in the cooler, wetter conditions of northern Europe, the sativum group in the warm, fertile areas of the Mediterranean and the sub-tropical and pekinese groups of the Indian sub-continent and China.

Horticulturally we recognise only two distinct groups - ophioscorodon (Allium sativum var. ophioscorodon) - often referred to as hardneck or topsetting garlic due to the fact that it produces a flower stalk, and the sativum or softneck garlics (Allium sativum var. sativum) which generally do not produce flower stalks. The wild longicuspis and more primitive varieties are typically included with the hardneck group as Purple Stripe and Porcelain varieties while the softneck group encompasses the pekinese and sub-tropical clones within its wide classification as Asiatics.

Individual plant characteristics such as leaf shape, number of cloves, length of flower stalk, dormancy, etc are an expression of the genetic make-up of specific clones. Within the plant cells, these outward differences are reflected in different levels and combinations of cell metabolites and it is some of these metabolites which give garlic its characteristic flavour and aroma. It must be remembered however that whilst a specific garlic clone has the potential to produce a bulb of a particular flavour profile, the formation of flavour-pre-cursors is a function of photosynthesis and as such is heavily modified by environment (temperature, light levels, sulphur availability, etc).  

When garlic is crushed, the flavour precursors within the cells are converted to a group of sulphur compounds called thiosulphinates. These are the primary flavour compounds of garlic and although a total thiosulphinate level is often used as a measure of overall garlic strength or pungency, there are actually ten different thiosulphinates which give each garlic clone its individual flavour ‘fingerprint’.

Geographical evolution of garlic varieties

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