A large basket of dark green leaves is probably the most unusual thing you might see at the curry spice stall. These are the leaves (bai ma-groot) of the kaffir lime tree. The leaves give off a strong lime aroma, and are an important ingredient in many Thai soups and curries, not to mention one of Chiang Mai's most famous foods, the spicy sausage called sai ooa. The leaves not only give their citrus taste to any dish, they also lend their strong fragrance. This is probably why the leaves are used in place of the zest, because Thais strongly believe that how a dish smells is as important as how it tastes. In fact, the senses of taste and smell are closely related, to the extent that they are really inter-twined – the aroma of a dish will affect your perception of how it tastes.
A basket of Kaffir Lime leaves on sale.
The leaves are a bit odd, in that they usually appear to be two heart-shaped leaves occupying a single stem end to end. The leaves are also a bit thick and fleshy. The fruit of the kaffir lime (ma-groot) itself is rather unusual as well, in that its green colored skin is very lumpy, quite unlike other citrus fruits. You may find the fruits on sale at the curry spice stall, since the zest is used in some Thai dishes. Herbal shampoos made from the kaffir lime are widely available in most supermarkets in Thailand. It is supposed to prevent dandruff. Some people even believe that the kaffir lime wards off evil spirits (like garlic to vampires) and hang it outside their house.