Common name: Nutmeg

Nutmeg is a spice tree believed to originate in the Moluccas Islands, a small group of islands in the Indonesian Archipelago that, according to botanists, is also home to the Clove tree (Syzygium aromaticum).

Today, the tree is widely distributed throughout South-East Asia and cultivated in many other humid tropical regions worldwide, including parts of India, Sri Lanka, Madagascar, Tanzania, Central America, and the Caribbean. It is cultivated for its fruit, the source of the well-known spice used for centuries to flavour sweet and savoury dishes, including baked goods, desserts and beverages, especially milk-based ones.

A medium-sized tree, it may reach up to 25 m (82 ft) tall, though in cultivation it 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 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 are oblong with a pointed tip, up to 15 cm (6 in) long, glossy dark green on top and pale green underneath. Alternately arranged along the stems at the ends of the branches, they remain on the tree in all seasons. When crushed, they release a sweetly spicy aroma.

The flowers are small, creamy-yellow, waxy, fleshy, and either female or male on separate trees. Male trees usually bear larger clusters of flowers. Still, it is difficult to distinguish the sex of the tree before it reaches maturity. Therefore, plants are mainly used as rootstock onto which cuttings from selected male and female trees are grafted.

Flowering occurs on and off throughout the year, with the flowers opening at night and emitting a sweet fragrance to attract moths, the tree's specialist pollinators. Fertilised female flowers develop into 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 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 nutmeg varieties. Still, fruit characteristics can vary considerably between trees in fruit shape and size, seed shape and size, and aril thickness and colour.

Split nutmeg fruit (Singapore)

Edible uses

Spice - Nutmeg flavouring comes from the dried kernel, extracted from the seed by cracking the shell after the whole seed has been thoroughly dried. The seed with the mace removed is traditionally dried in the sun until the kernel rattles in the shell, a process that takes about a week.

In today's commercial operations, the drying process is more technologically advanced, with the seed dried indoors under forced-air conditions. Dried nutmeg kernels are used worldwide, either whole and freshly grated or powdered, to flavour sweet and savoury dishes.

In colonial Britain and still today, it is used to spice traditional alcoholic drinks, such as mulled wine, and traditional milk-based desserts and beverages, such as junket and eggnog. It is also a common ingredient sprinkled atop freshly baked pies like apple and pumpkin, atop fondue and other creamy cheese sauces, and in classic milk-based sauces such as bechamel.

Mace, the part of the fruit wrapped around the seed, is also traded as a spice. After separating it from the seed, it is usually dried for only a few hours to maintain its crimson colour. Mace is mainly used as a nutmeg replacement and, although weaker, has a more complex flavour.

Jam or marmalade - The fruit pulp is aromatic, fleshy, and juicy and is made into jam and jelly.

Fruit conserve - As well as other fruit preserves.

Material uses

Essential oil - The dried kernels, rejected for one reason or another, are crushed and converted into nutmeg oil or nutmeg butter. Steam distillation extracts nutmeg oil, a volatile, pale yellow essential oil, from the crushed material. Mace oil, a pale yellow oil, is similarly extracted from mace by steam distillation. Yields of nutmeg oil and mace oil average 8% and 9%, respectively, based on the weight of material processed.

Natural flavouring - Nutmeg oil is used to flavour food, drinks, medicines, tobacco, and toothpaste.

Natural fragrance - Nutmeg oil is also commonly used to lend a spicy or masculine note to perfumes, colognes and grooming waters. It is found in fragrances such as 'Blue Grass', 'Panthère' and 'Sybaris'. Mace oil is similarly sometimes used as a fragrance in sandalwood-type soaps and potpourri mixes.

Natural carrier base - Nutmeg butter, a highly aromatic yellow fat with a consistency similar to dairy butter, is extracted by pressing crushed kernels between heated plates in a steamer, with yields averaging 30% of the weight of the material processed. It is used mainly as a base for ointments.

Health use

​Natural digestive aid - Nutmeg essential oil contains high levels of myristicin, a compound known for its stimulating and soothing effects on the digestive tract. It achieves this by increasing gastric juice flow, thereby improving appetite and digestion. Its anaesthetic and anti-inflammatory effects help reduce nausea, vomiting and diarrhoea.

Nutmeg seed

Grated nutmeg​​

Climate

Nutmeg 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 1200 to 6000 mm and a dry season of 3 months or less.

Irrigation can 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 microclimate in which irrigation can be misted over the top of their canopy.

Nutmeg fruits at elevations from sea level 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.

Growing

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, then graft them onto seedling rootstock. Usually, this is around one male tree for every ten female trees to ensure good pollination and fruit production.

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 7.5, and on sites with partial to full sun exposure. However, young plants need shade for the first few years of life to prevent sun scorch. It is common 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 at 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. However, 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 about 808 kg per hectare (720 lb per acre), and dried mace average about 168 kg per hectare (150 lb per acre).

Problem features

Nutmeg trees produce abundant fruit, but the seeds are large and not easily dispersed. Despite widespread cultivation, there appears to be no record of it as a weed or invasive species anywhere. The Hawaii Pacific Weed Risk Assessment (HPWRA) project assesses it as a low weed-risk species for Hawaii.

In extreme cases, overconsumption of nutmeg can cause skin flushing, irregular heartbeat, stupor, and delirium. It can also irritate the skin, causing contact dermatitis in some people.

Books

• Adams, C. D. 1972, Flowering plants of Jamaica, University of the West Indies, Mona, Greater Kingston

• Arctander, S. 1960, Perfume and flavor materials of natural origin, Elizabeth, New Jersey

• Attokaran, M. 2011, Natural food flavors and colorants, Institute of Food Technologists, Wiley-Blackwell Publishing, Oxfordshire

• Barwick, M., et al. 2004, Tropical & subtropical trees : a worldwide encyclopaedic guide, Thames and Hudson, London

• Brady, G. S. & Clauser, H. R & Vaccari, J. A. 2002, Materials handbook : an encyclopedia for managers, technical professionals, purchasing and production managers, technicians and supervisors, 15th ed., McGraw-Hill, New York

• Chevallier, A. 2000, Encyclopedia of herbal medicine, 2nd American ed., Dorling Kindersley, New York

• Culbreth, D. M. R. 1927, A manual of materia medica and pharmacology : comprising the organic and inorganic drugs which are or have been recognized by the United States pharmacopeia, 7th ed., Febiger, Philadelphia

• Fawcett, W. 1891, Economic plants, An index to economic products of the vegetable kingdom in Jamaica, Jamaica Government Printing Establishment, Kingston

• Groom, N. 1997, The new perfume handbook, 2nd ed., Blackie Academic & Professional, London

• Guenther, E. & Althausen, D. 1948 to 1952, The essential oils (6 volumes), Van Nostrand Publishing, New York

• Jensen, M. 1999, Trees commonly cultivated in Southeast Asia : an illustrated field guide, 2nd ed., Food and Agricultural Organisation of the United Nations (FAO) Regional Office for Asia and the Pacific (RAP), Bangkok

• Khan, I. A. & Abourashed, E. A. 2010, Leung's encyclopedia of common natural ingredients : used in food, drugs and cosmetics, 3rd edition, Wiley Publishing, Hoboken, New Jersey

• Macmillan, H. F. 1943, Tropical planting and gardening : with special reference to Ceylon, 5th ed, Macmillan Publishing, London

• Polunin, Ivan 1987, Plants and flowers of Singapore, Times Editions, Singapore

• Standley P. C., & Steyermark J. A. 1946 to 1976, Flora of Guatemala (25 volumes), Botany series publication (Chicago Field Museum of Natural History), Chicago, Illinois

• Weiss, E. A 2002, Spice crops, CABI Publishing, Wallingford, United Kingdom

Articles, Journals, Reports and Working Papers

• Watson, B.J., & Moncur, M. 1985, Guideline criteria for determining survival, commercial and best mean minimum July temperatures for various tropical fruit in Australia (Southern Hemisphere), Department of Primary Industries Queensland (DPI QLD), Wet Tropics Regional Publication, Queensland