A Vetiver hedge slows down and spreads out rainfall, allowing it to filter through gently, without taking soil and silt with it. The deep, dense, spongy root system acts like reinforcing steel in concrete, protecting the soil under the plant and preventing terraces from collapsing. The roots also have a strong aromatic oil and are repellent to rats and other pests. The leaves are unpalatable to livestock and the hedge grows impenetrable for trespassers and even snakes. Or it can be cut back each year to prevent shading, with the leaves used as a mulch for trees to help retain moisture and deter insects. It is also practically sterile so it does not spread like a weed in farmers' fields.
Vetiver grass can grow almost anywhere. Although it is a subtropical plant, indigenous to parts of Asia, it has been grown successfully under snow in the Himalayas and in the African Sahel. The Masdar Group agricultural consultancy in Wokingham have Vetiver nurseries under way in Zimbabwe, Zambia and the Sudan. The grass can withstand fires, floods and droughts. Richard Grimshaw, World Bank Chief of the New Delhi Agriculture Division, says that it has 'survived under very, very dry, nearly drought conditions. It is the only grass which has survived, where everything else has died or been eaten flat.'
A Vetiver hedge is permanent, and after the third year requires no maintenance. Farmers can do all the work involved themselves, so it is between ten and a hundred times cheaper than the traditional soil erosion measure of building earthbanks - the latter can involve mechanical diggers, can burst in heavy rainstorms, erode and melt away in time and take a wide strip of land out of production.
The World Bank is hardly renowned for its ecological awareness, but the promotion of Vetiver grass seems to be a step in a more positive direction.
Their field workers' booklet about it is available for 50p in stamps from the World Bank, New Zealand House, Haymarket, London SW1.