CLIMATE AND SOIL. In India, cardamom grows under natural conditions of the evergreen forests in the Western Ghats. It thrives best in tropical forests at altitudes ranging from 600-1500 metres, receiving a well-distributed rainfall of over 150 cm and a temperature of 10o-35oC. its optimum growth and development is observed in warm and humid places under the canopy of lofty, evergreen forest trees. It is highly sensitive to wind and drought and, therefore areas liable to be affected by these conditions are unsuitable. Water-logging or excessive moisture is equally injurious. The ideal site is a sloping land with good drainage. The crops is raised chiefly on well-drained, rich forest loam, and red, deep, good-textured lateritic soils having plenty of humus or leaf-mould.
PREPARATION OF LAND If virgin forest areas are selected for a plantation, they are too be cleared of all undergrowth and trees not suitable for furnishing heavy shade needed by cardamom. Where tree growth is sparse and shade insufficient or unsatisfactory, quick-growing trees such as Erythrina are planted for temporary shading and other tall and spreading trees for permanent shade. When grown as a subsidiary crops in areca and coffee plantation, the main crops furnishes the required shade.
The spacing commonly adopted for the ‘mysore’ type varies from 2m X 2m to 3m X 3m and for the less vigorous ‘Malabar’ type it varies from 1.5m to 2.2m between the plants and the rows. The seedlings are planted in pits of about 60cm X 60cm X 35cm filled with a mixture of surface soil and compost or well-rotted cattle manure. For planting in areca gardens, the north Kanara system of digging trenches instead of individual pits is adopted.
PROPAGATION. Cardamom is propagated through suckers or seedlings. However the latter method is preferable in order to check the spread of the virus disease ‘katte’. In the case of vegetative propagation 3-5 bulbs of 1/2. to 2-year-old clumps obtained from healthy and regularly high-yielding stock are planted in each pit. For raising a nursery, the present practice is to collect the seeds from disease-free, high yeilding plants with compact-panicles. The capsules selected for seeds should be fully mature and preferably from the second or third round of picking. They should immersed in water and gently pressed for rejecting the seeds, which should then be washed well in cold water.
After draining the water the seeds should be mixed with ash and dried in shade in 2 or 3 days. To ensure uniform and early germination, seeds should be sown after extraction. They are to be broadcast on nursery-beds of 1m X 6m and raised to a height of about 30 cm. The selection of the site for the nursery-beds is very important. The site should have a gentle slope and there should be adequate facilities for irrigation. The soil should be fertile and rich in humus. The seed-rate commonly used is 10g per square metre of the germination bed. After sowing, the seeds should be covered with a thin layer of fine sand or soil and then mulched to a thickness of about 2 cm with paddy straw or any other suitable material. The bed should be watered twice a day. Germination will commence in about 30 days and may continue for a month or two. The mulch should be removed after the commencement of germination. Shade should be provided for the young seedlings by erecting a pandal. In Kerala and Tamil Nadu seedlings are transplanted in a secondary nursery when they are about six months old, allowing a spacing of about 25 to 30 cm. in the case of 3-4 rows per bed. In Karnataka, generally the seedlings are not transplanted in a secondary nursery. They are allowed to remain in their germination-beds for about ten months, after which they are planted in the main field. Spraying with 1% Bordeaux mixture keeps the seedlings disease-free. About 1 kg of seeds would produce enough seedlings for planting one hectare.