I'd heard of curry leaves for quite a long time before I realised that they were a genuine spice. Prior to that I'd assumed the term was a culinary joke.
Curry leaf trees
Curry leaf fruits
The curry tree is native to the Indian subcontinent where it can be found wild (or escaped from cultivation) almost everywhere, excluding the higher levels of the Himalayas. In the East its range extends into Myanmar.
The leaves. Although often sold dried, they lose their delicate fragrance in the drying process and should be used fresh.
Rutaceae (citrus family).
Fresh and pleasant, slightly reminiscent of tangerines.
The English term "curry" is of Indian origin and was introduced to Britain during the Raj. In Tamil (the predominant South Indian language) the word kari means "soup" or "sauce" and this is the basis of the Tamil name for curry leaf, kariveppilai, which contains ilai "leaf". In English usage, "curry" has a wider meaning encompassing not only spicy foods of various kinds, but also Indian-style spice mixtures (as in curry powder).
In North Indian (Aryan) languages, curry leaf is usually denoted by the Tamil name or an adaptation thereof, for example Hindi karipatta and or Bengali karhi-pat or Sinhala karapincha. The same first element is also found in Marathi kadhi-limb, from limbu (lemon). The botanical name murraya koenigii is in tribute to two collaborators of Linnaeus, Swedish botanist Johan Murray (1740-1791) and Danish botanist J.G. Koenig (1728-1785).
Curry leaves are extensively used in South India and Sri Lanka (and are necessary for the authentic flavour of dishes of the southern subcontinent), but are also of some importance in North India. Taken by South Indian migrants, curry leaves reached Malaysia, South Africa and Réunion island, but outside of the Indian sphere of influence they are rarely found.
Curry powder is a British invention designed to imitate the flavour of Indian cooking with minimal effort. Some curry powder contains curry leaves, but they cannot play a significant role as dried curry leaves lose their fragrance within days. A typical curry powder should derive its taste mainly from roasted cumin, coriander and fenugreek, black pepper and chillies, with the possible addition of dried ginger, ajwain and/or celery (as a substitute for Indian radhuni). A sweeter powder more suited to Mogul dishes would add cinnamon, cloves, green cardamom and Indian bay leaves). The yellow colour stems from turmeric (Hindi name haldi) rather than from saffron. These recipes represent a British compromise between the North Indian garam masala and the South Indian sambar podi mixtures. Curry powder has been introduced to some Far Eastern countries in the past and today plays but a minor role as a flavouring in China, Indonesia and Vietnam.
In Indian cuisines, curry leaves are almost always used fresh, but for a few recipes the leaves should be oven-dried or toasted immediately before use. Another common technique is short frying in ghee or oil. Since South Indian cuisine is predominantly vegetarian, curry leaves seldom appear in non-vegetarian food. The main applications are dhals, vegetable curries (sambaar) and stuffings for the crispy samosa. Because of their soft texture the leaves are not removed before serving and can be eaten safely.