Nutmeg is a spice tree believed to originate from the Moluccas Islands, a small group of islands in the Indonesian Archipelago, which according to botanists, is also the home of the Clove Tree (Syzygium aromaticum).
Nowadays, the Nutmeg Tree is widely distributed throughout South-East Asia and is cultivated in many other humid tropical regions across the world, including parts of India, Sri Lanka, Madagascar, Tanzania, Central America and the Caribbean. It is cultivated for its fruit, which is the source of the well-known spice. For centuries, nutmeg has been used to flavour sweet and savoury dishes, particularly baked goods, desserts and beverages, especially milk-based ones.
A medium-sized tree, it may reach heights of up to 25 m (82 ft), though in cultivation is more typically 5 to 15 m (16 to 50 ft) tall. The trunk is usually straight and slim, up to 30 cm (1 ft) in diameter, and supports a densely leafy crown. On open sites, young trees develop a pyramidal-shaped crown that with age becomes more rounded and wide-spreading. The bark is brownish-grey, smooth and on wounding exudes a sticky, lightly-red coloured gum.
Leaves oblong with a pointed tip, up to 15 cm (6 in) in length, glossy dark green on top and pale green underneath. They are alternately arranged along the stems at the ends of the branches and remain on the tree in all seasons. When crushed, they release a sweetly spicy aroma.
The flowers are small, creamy-yellow, waxy, fleshy and with female and male flowers on separate trees. Male trees usually bear clusters with more flowers, but it is difficult to distinguish the sex of the tree before it reaches maturity. Therefore, plants grown from seed are most often used as rootstock to graft-on cuttings from selected male and female trees.
Flowering occurs on and off throughout the year, with the flowers opening at night and emitting a sweet fragrance to attract moths, the trees specialist pollinators. Fertilised female flowers are followed by pale-green, pear-shaped or roundish fruit 4 to 5 cm (1.5 to 2 in) in diameter. When ripe, the fruit becomes pale yellow then splits lengthwise to expose a single, large oval seed wrapped in a crimson netting. This netting or aril is the source of mace, the lesser-known of the two spices produced from the fruit. Inside the seed is a large fleshy kernel, which is the nutmeg of the spice trade.
There are no officially recognised varieties of nutmeg, though there can be considerable variation in fruit characteristics between trees, in terms of fruit shape and size, seed shape and size, and aril thickness and colour.
Split nutmeg fruit (Singapore)
Nutmeg flavouring comes from the dried kernel, which is extracted from the seed by cracking open the shell after the whole seed has been thoroughly dried. The seed with the mace removed is traditionally dried under the sun until the kernel rattles in the shell and this takes about a week of drying to achieve. In commercial operations today, the drying process is more technologically advanced, with the seed dried indoors under forced-air conditions.
Dried nutmeg kernels are widely used around the world, either whole and freshly grated or in powdered form, to flavour both sweet and savoury dishes. In colonial Britain and still today, it is used to flavour traditional alcoholic drinks, such as mulled wine and traditional milked-based desserts and beverages, such as junket and egg-nog. It has also become an indispensable ingredient sprinkled atop fondue and other creamy cheese sauces just before serving, as well as atop classic milk-based sauces such as béchamel, and freshly baked pies such as apple and pumpkin.
The dried kernels that are rejected for one reason or another are crushed and converted into nutmeg oil or nutmeg butter. Nutmeg oil, a volatile, pale yellow essential oil, is extracted by steam distillation of the crushed material. It is widely used by the food, beverage and pharmaceutical industries as a flavouring in food, drinks, medicines, tobacco and toothpaste. Nutmeg oil is also commonly used in perfumery to give perfumes, colognes and grooming waters a spicy or masculine note. It is found in popular fragrances such as 'Blue Grass', 'Panthère' and 'Sybaris'.
Nutmeg butter is a highly aromatic yellow fat similar in consistency to dairy butter and is extracted by pressing the crushed kernels between heated plates in a steamer. It is mostly used as a base for ointments.
Mace, which is the part of the fruit that is wrapped around the seed is also traded and used as a spice. After separating from the seed, it is usually dried, but only for a few hours so that it maintains its crimson colour. Most mace is used as a nutmeg replacement and although weaker has a more complex flavour. Mace oil, a pale yellow oil extracted by steam distillation, is sometimes used as a fragrance in sandalwood-type soaps and potpourri mixes.
Yields of nutmeg oil, mace oil and nutmeg butter average 8%, 9% and 30% respectively, based on the weight of the material processed.
The fruit pulp is aromatic, fleshy and juicy, and after removing the seed can be made into jam, jelly and fruit preserves.
Nutmeg essential oil contains high levels of the compound Myristicin, which is known to have both a stimulating and soothing effect on the digestive tract. It achieves this by increasing the flow of gastric juices, leading to improved appetite and digestion, and its anaesthetic and anti-inflammatory effects help reduce nausea, vomiting and diarrhoea.
Grows naturally in humid tropical climates, generally frost-free areas with annual lows of 18 to 25 °C, annual highs of 27 to 35 °C, annual rainfall of 1400 to 6000 mm and a dry season of 3 months or less.
Irrigation can be used to extend Nutmeg cultivation to areas having a dry season lasting up to 5 months. When grown under drier-than-normal conditions, the trees benefit from a micro-climate where irrigation can be misted on them over the top of their canopy.
Nutmeg is known to fruit at elevations up to 1000 m (3280 ft) in Kerala (South India), where the average low of the warmest month is 19 °C (66 °F) or above.
New plants can be started from seed or cuttings, but the sex of the seedlings is not easily determined, so cuttings are preferred. Good practice is to select cuttings from known male and female trees and then graft these onto seedling rootstock. Using this method, a known amount of male and female trees can be determined and can then be planted at a ratio that will give good pollination and fruit production. Usually, this is around one male to every ten female trees.
Performs best on rich, free-draining clay-loam, loam, sandy-loam and loamy-sand soils of a moderately acid to slightly alkaline nature, generally with a pH of 5.5 to 7.5m, and on sites with partial to full sun exposure. However, the young plants need shading for the first few years of life to prevent sun-scorching and it is common practice to plant them under a fast-growing, short-lived perennial, such as Banana (Musa acuminata).
Nutmeg trees are slow to mature, only starting to flower and fruit when around five to nine years old, but will continue to do so for many decades.
Individual nutmeg trees yield on average about 9 kg (20 lbs) of dried kernels per year, though some trees may yield much more depending on the tree maturity and growing conditions. In Grenada, where nutmeg is grown commercially, yields of dried kernels average around 808 kgs per hectare (720 lbs per acre) and dried mace around 168 kg per hectare (150 lbs of per acre).
Nutmeg trees produce abundant fruit, but the seed are large and not easily dispersed. Despite its widespread cultivation, there does not appear to be any record of it anywhere as a weed or invasive species. It is assessed as a low weed risk species for Hawaii by the Hawaii Pacific Weed Risk Assessment (HPWRA) project.
In extreme cases, overconsumption of nutmeg can cause flushing of the skin, irregular heartbeat, stupor and delirium. And it is an irritant to the skin, in some people causing contact dermatitis.
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