The nutmeg tree is unique among spices as the donor of two distinct spices of commerce. Nutmeg is the seed of an apricot-like fruit of the nutmeg tree and mace is its aril a thin leathery tissue spread over the seed coat. Both spices are strongly aromatic, resinous and warm in taste. Mace is generally said to have a finer aroma than nutmeg. Nutmeg quickly loses its fragrance when ground. Commercial part of this tree spice is seed.Naturally, nutmeg is limited to the Banda Islands, a tiny archipelago in Eastern Indonesia (Moluccas)
The nutmeg tree is a large evergreen tree spice belonging to Myristicaceae familyand grows to a height of about 18 m. It produces fruits eight to nine years after planting. The fruit of nutmeg tree, which is similar in colour and size to apricot, splits when ripe revealing the brilliant red arils encasing the brown nut. The red arils on drying become orange in colour and are the mace of commerce. The nut is also dried until the kernel inside rattles.
Climate and soil
Nutmeg requires a hot, humid climate without pronounced dry season, with an annual rainfall of 150 cm and more. It grows well from sea level up to about 1300 m above sea level. Areas with clay loam, sandy loam and red laterite soils are ideal for its growth. The soil should be rich in organic matter and well drained. The tree prefers partial shade. Sheltered valleys are the best suited. It can be grown up to about 900 m above MSL. Both dry climate and water logged conditions are not suitable for nutmeg cultivation.
IISR-Viswashree is the only known variety. Important characters are early bearing with potential yield at 25th year. Fruits in clusters (4-5). Nut dry recovery 70%, Mace dry recovery 35% yield from 8th year old tree-1000 fruits; 1.33 kg mace;9kg dry nut.
Fully ripened tree-burst fruits are selected for raising seedlings. The fleshy rind and the mace are removed before sowing. The seeds should be sown immediately after collection. If there is any delay in sowing, the seeds should be kept in baskets filled with damp soil. The seedbeds of 100-120 cm width, 15 cm height and of convenient length may be prepared in cool and shady places. A mixture of garden soil and sand in the ratio 3:1 may be used for preparing nursery beds. Over this, sand is spread to a thickness of 2-3 cm and the seeds dibbled 2 cm below the surface at a spacing of about 12 cm on either side. Seeds germinate within 50-80 days after sowing. When the plumule produces two elongated opposite leaves, the seedlings are to be transferred from beds to polybags.
Since the nutmeg trees require shade, suitable fast growing shade trees like Albizia, Erythrina etc. are planted in advance. Banana can also be grown as a shade crop in the early stages. Pits of 90 x 90 x 90 cm are dug at a spacing of 8 x 8 m with the onset of southwest monsoon. The pits are filled with topsoil and compost or well-decomposed cattle manure and seedlings are planted.As nutmeg is cross-pollinated, considerable variations are observed in the crop. The plants differ not only for all aspects of growth and vigour, but also for sex expression, size and shape of fruit and quantity and quality of mace. An important problem in nutmeg cultivation is the segregation of seedlings into male and female plants resulting in about 50% unproductive male trees. The only alternative is to adopt vegetative propagation either by top-working male plants or using budded or grafted plants.
Due to sex problems and long prebearing period of seedlings, now-a-days grafts are preferred for planting. For raising rootstocks, naturally split healthy fruits are harvested during June-July. The seeds are extracted from the pericarp and sown immediately in sand beds of convenient length, 1 to 1.5 m width and 15 cm height. Regular watering is necessary for good germination. Germination may commence from about 30th day and last up to 90 days after sowing. About 20 days old sprouts are transplanted to polythene bags containing a mixture of soil, sand and cow dung (3:3:1).
The selected rootstock at the first leaf stage should have a thick stem (diameter of 0.5 cm or more) with sufficient length so as to enable to give a cut of 3 cm length. Scions from upright growing shoots with 2-3 leaves, collected from high yielding trees can be used for grafting. The stock and scion should approximately have the same diameter. A “V ” shaped cut is made in the stock and a tapered scion is fitted carefully into the cut. Bandaging at the grafted region may be done with polythene strips. They are then planted in polythene bags of 25 cm x 15 cm size containing potting mixture. The scion is covered with a polythene bag and kept in a cool shaded place protected from direct sunlight. After 1 month, the bags can be opened and those grafts showing sprouting of scions may be transplanted into polythene bags, containing a mixture of soil, sand and cow dung (3:3:1) and kept in shade for development. The polythene bandage covering the grafted portion can be removed after 3 months. During grafting, precautions should be taken to prevent wilting of scions and to complete the grafting as soon as possible. The grafts can be planted in the field after 12 months.
Preparation of land and planting
Planting in the main field is done at the beginning of rainy season. Pits of 0.90 m x 0.90 m x 0.90 m size are dug at a spacing of 8 m x 8 m and filled with organic manure and soil about 15 days earlier to planting. For planting plagiotropic grafts, a spacing of 5 m x 5 m has to be adopted. A male plant has to be planted for every 20 female plants in the field.
The plants should be shaded to protect them from sun scorch during early stages. Permanent shade trees are to be planted when the site is on hilly slopes and when nutmeg is grown as a monocrop.
Nutmeg can best be grown as an intercrop in coconut gardens that are more than 15 years old where shade conditions are ideal. Coconut gardens along river beds and adjoining areas are best suited for nutmeg cultivation. Irrigation is essential during summer months.
Apply 10 kg cattle manure or compost per seedling during the first year. Increase the quantity gradually till a well-grown tree of 15 years and above receives 50 kg of organic manures per year. Apply N:P2O5:K2O @ 20:18:50 g/plant during the first year. This may be doubled in the next year. Gradually increase the N:P2O5:K2O dose to 500:250:1000 g/plant/year to obtain full dose from 15th year onwards.
Black scale(Saissetia nigra)
The black scale infests tender stems and leaves especially in the nursery and sometimes-young plants in the field. The scales are clustered together and are black, oval and dome shaped. Black scales feed on plant sap and severe infestations cause the shoots to wilt and dry. It can be controlled by spot spraying with quinalphos 0.025%.
White scale (Pseudaulacaspis cockerelli)
The white scale is greyish white, flat and shaped like a fish scale and occurs clustered together on the lower surface of leaves especially in nursery seedlings. The pest infestation results in yellow streaks and spots on affected leaves and in severe infestations the leaves wilt and dry.
Shield scale (Protopulvinaria mangiferae)
The shield scale is creamy brown and oval and occurs on tender leaves and stems especially in nursery seedlings. The pest infestation results in wilting of leaves and shoots.
The scale insects mentioned above and other species that may also occur sporadically on nutmeg can be controlled by spraying dimethoate 0.05% or quinalphos 0.025%.
Leaf spot and shot hole (Colletotrichum gloeosporioides)
Sunken spots surrounded by a yellow halo are the initial symptoms. Subsequently the central portion of the necrotic region drops off resulting in shot hole symptoms. Dieback symptoms are also observed in some of the mature branches. On young seedlings drying of the leaves and subsequent defoliation are seen. The disease can be controlled by spraying 1% Bordeaux mixture two or three times during rainy season.
Two types of blights are noticed in nutmeg. The first one is a white thread blight wherein fine white hyphae aggregate to form fungal threads that traverse along the stem underneath the leaves in a fan shaped or irregular manner causing blight in the affected portions. The disease is caused by Marasmius pulcherima. The dried up leaves with mycelium form a major source of inoculum for the spread of the disease.The second type of blight is called horse hair blight. Fine black silky threads of the fungus form an irregular, loose network on the stems and leaves. These strands cause blight of leaves and stems. However, these threads hold up the detached, dried leaves on the tree, giving the appearance of a bird’s nest, when viewed from a distance. This disease is caused by Marasmiusequicrinus. Both the diseases are severe under heavy shade.
These diseases can be managed by adopting phytosanitation and shade regulation. In severely affected gardens, Bordeaux mixture 1% spraying may be undertaken in addition to cultural practices.
Immature fruit split, fruit rot and fruit drop are serious in a majority of nutmeg gardens in Kerala. Immature fruit splitting and shedding are noticed in some trees without any apparent infection. In the case of fruit rot, the infection starts from the pedicel as dark lesions and gradually spreads to the fruit, causing brown discolouration of the rind resulting in rotting. In advanced stages, the mace also rots emitting a foul smell. Phytophthora sp. and Diplodia natalensis have been isolated from affected fruits. However, the reasons for fruit rot could be both pathological and physiological.
Bordeaux mixture 1% may be sprayed when the fruits are half mature to reduce the incidence of the disease.
Fruits are available throughout the year, but the peak period of harvest is fromJune to July . When fruits are fully ripe, the nuts split open. These are either plucked from the tree or allowed to drop. The two major products are nutmeg and mace. Dried nutmeg and mace are directly used as spice and also for the preparation of their derivatives. After de-rinding the nutmeg fruit, red feathery aril (mace) is separated from pericarp. The mace is detached, flattened and dried under sun on mats for 3-5 days. The nuts are dried in the sun for six to eight days till they rattle in their shell. They are stored in warm dry place prior to shelling.
Nutmeg and mace oleoresins are prepared by extracting the ground spice with organic solvents. Yield of oleoresin is 10-12 per cent for nutmeg and 10-13 per cent for mace. Mace oleoresin possesses a fine, fresh fruity character.
Nutmeg contains 25-40 per cent of fixed oil that can be obtained by pressing the crushed nuts between plates in the presence of steam or by extracting with solvents. The product, known as nutmeg butter, is a highly aromatic, orange coloured fat with the consistency of butter at ambient temperature.
This is obtained as pale yellow to white volatile liquid possessing a fresh warm aromatic odour. The yield ranges from 7 to 16 %. The unshelled nuts are coarsely crushed in a mechanical cracker and steam distilled.
The mace yields 4-17 % colourless to pale yellow liquid possessing organoleptic properties similar to nutmeg oil. Nutmeg and mace oil are also used for flavouring.