Vetiver – Natural Erosion and Flood Control

Vetiver is a plant native to India which is now extensively used for erosion and flood control in over 70 countries worldwide.

Rick Fisher was friends with a chap who worked for New Zealand’s then DSIR, Department of Scientific and Industrial Research. That friend had become familiar with a plant being introduced to New Zealand for the purpose of flood and soil erosion control. It had no rhizomes and no seeds and could only be propogated by splitting a plant and growing the new one. It cannot reproduce unassisted.

Introduction of Vetiver into New Zealand

Rick’s friend insisted that he should develop Vetiver because it was the perfect answer to many of the flood and erosion issues NZ faced. Under this pressure, Rick agreed. He began with two plants in 1998, splitting and growing, and splitting again until today when he now grows fifty thousand vetiver plants every year. In terms of erosion control, this number of plants equates to a hedge of 10kms.

Vetiver System

John Greenfield was the designer of what has become known as the Vetiver System which is a specific method of planting vetiver to achieve soil and flood control. He introduced it to more than 70 erosion or flood prone countries worldwide and it is extensively used in those countries for river bank control, stream bank stabilisation as well for terracing and rice paddies.The plant produces a complex root system which will grow up to five metres deep within three or four growing seasons in soil, sand, clay, shale, or any other medium into which it is transplanted.

In NZ engineers are starting to take a serious interest in Vetiver as a way of reinforcing earthworks.

Vetiver is a Tough Plant

Able to resist a deep drought for up to eighteen months, Vetiver is just as flexible when it is submerged and can remain under water for up to three months without damage.

The plants grow readily to approximately 60cm wide and up to a maximum of 180cm tall, never exceeding these dimensions. Once they reach maturity at around three years old they can be grazed right to the ground and will spring happily away again. Stock generally do not prefer it to grass, although some cows love it, but they will readily eat it when more appealing feed isn’t available. It does them no harm and provides feed in drought conditions.

Erosion and Flood Control

Rick Fisher says, “90% of erosion is caused by flooding. Because Vetiver has such thick foliage and an incredibly complex root structure, flood water is held back by the vegetation to a very controlled filtration rate, minimising the speed and volume at which water runs over erosion prone land. Testing proved that a 61cm flume of water which flowed at 28 litres per second was contained behind a mature vetiver hedge to create a pond of 30cm depth, before draining gently away.

Because it is a tropical plant, Vetiver is mainly used in the northern half of the North Island where it is not exposed to snow and frost. It will sustain a -14 frost but not snow, and growth more-or-less stops over winter months. In the summer with sufficiently warm conditions vetiver can grow as much as 5cms a day while the roots will reach deeper into the ground at the rate of 5cm per week.

Vetiver – Fungicide, Pesticide, Perfume Ingredient

Vetiver is a well-known flea repellant in some countries and is used as a fungicide as well as a pesticide. Grown near other crops, it protects them from fungal and pest attack. It is also a well-known ingredient in perfume manufacture although in NZ it does not grow fast enough, compared to tropical countries, to provide the kind of growth suitable for perfumes.

Rick has spent many hours travelling around New Zealand educating councils and engineers on the uses and tremendous value of of the C4 plant, Vetiver, and he says that now, it is slowly being recognised and more widely used.

 

Source: Theresa Sjoquist interview with Rick Fisher

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