Reproduced, with permission, from:
Reijntjes, C., B. Haverkort, and A. Waters-Bayer. 1992. Farming for the future: An introduction to low-external input and sustainable agriculture. London: Macmillan.
Betel vine plants (Piper betle) require a cool climate and high humidity during their life span of 2 - 3 years. If the plants are exposed to extreme heat, the leaves become dark green and brittle. If a cool climate and shade are created in the garden, the leaves will be light green and feathery and will fetch a good price in the market.
Farmers in Southern India therefore manipulate the climate in the garden to provide the necessary coolness. They dig long trenches 2.5 feet deep, 2 feet wide and 3 feet apart, on the edges of which they plant agathi (Sesbania grandiflora). After the agathi plants have grown 6 feet high, betel vine cuttings are planted beside them. As the agathi plants grow taller, they form a canopy which diffuses sunlight. The trenches are impounded with water 2 feet deep. By means of splash irrigation from the trenches, the soil for the betel vine is always kept moist. The garden borders are completely closed by dried banana leaves or plaited coconut leaves. The hot air outside is thus prevented from entering the garden and the dense canopy of the full-grown agathi plants provides a cool phytoclimate. The water in the trenches increases the humidity within the garden. All in all, the garden acts like a cool, air-conditioned room and the betel vine grows luxuriantly with broad, light green, feathery leaves (Balasubramainam 1987).