It's no beauty queen – the stems are long, scrawny and leafless and the pods dangle from the twigs like scorched testicles. Untreated, the seeds are so poisonous that as few as three can kill, while even a small amount induces nausea – hence the jatropha plant's nickname, "black vomit nut".
Despite its unprepossessing appearance, jatropha, whose pods contain inflammable oil, is one of a range of plants being intensively cultivated as biofuels. As it can grow in impoverished soil, requires little water and is inedible, its supporters claim that it cannot be said to be taking the place of food crops.
But now all biofuels, even the humble jatropha, are in the firing line. At the UN's world food summit in Rome yesterday it became clear that the responsibility of biofuels for soaring food costs that have sparked riots in 40 countries is the biggest point of contention. The US, which subsidises farmers to grow corn for ethanol production, claims biofuels account for less than 3 per cent of the 43 per cent rise in food costs over the past year. But the International Food Policy Research Institute said that they contributed 30 per cent to the rise between 2000 and 2007, while the International Monetary Fund says the figure is between 15 and 30 per cent.
Yesterday, the defenders of biofuels had their backs to the wall. "It is frightening to see attempts to draw a cause and effect relationship between biofuels and the rise of food prices," said President Luiz Inacio Lula da Silva of Brazil, which has been growing corn for ethanol for decades. "It offends me to see fingers pointed against clean energy from biofuels, fingers soiled with oil and coal."
Sir John Holmes, the British diplomat who heads a UN taskforce on the issue, said: "Biofuels are not taking the food out of the mouths of people, but we need to make sure that a balance is struck."
But on the fringes of the summit, campaigners claimed that even the jatropha bush is doing just that – depriving millions of the poorest farmers of the ability to feed themselves and their communities.
Henk Hobbelink, a Dutch agronomist with Grain, a non-governmental organisation that promotes sustainable agricultural biodiversity, said: "Jatropha has been presented as a way for poor farmers to produce fuel for themselves, and as a cash crop, by planting it on waste land. But what's happening is quite different from that. A handful of big corporations are growing jatropha in huge plantations, in optimum soil conditions and using a lot of water, to maximise the yield. Poor farmers who grow it on impoverished soil find they can't get into the market."
In India, jatropha farming has been heavily promoted by big companies as a way to help India achieve self-sufficiency in diesel production. But as usual the victims are the poor peasants. Shalini Bhutani, another member of Grain, said: "The first areas being targeted are the so-called 'wastelands', which gives the idea that the country will put to good use something that produces nothing at the moment... But what may look like barren pieces of land to outsiders provide sustenance for millions of people. They are the 'commons' and pasture lands of many communities."
The wasteland category, said Ms Buthani, also "covers almost all the 'orans' – traditional sacred groves – that are the lifeline of the 7.5 million pastoralists in Rajasthan". Tribal pasture in Orissa and Chhattisgarh is also being consumed.
Mr Hobbelink agrees that biofuels make sense for national governments trying to find sustainable fuel sources not subject to the price and supply vagaries of oil. "But if creating energy security means taking land from poor farmers – in countries like India where the government claims to be committed to helping people stay on the land – it just causes more problems," he said. And huge monoculture plantations cause just the same sort of pressure on ecosystems as other plantation monocultures like palm oil.
"The jatropha case just shows there is no easy way out of the present crisis," he said. "The only possible solution is to reduce fuel consumption."
Jatropha – the facts
* Dubbed the 'Wonder Plant', jatropha – which originated in Africa – is an inedible weed which has seeds that can be refined into biofuel.
* The poisonous plant's particular appeal is its hardiness; it can survive three years of drought and does not require high-quality soil to flourish.
* Notable supporters include the former senior economist to the World Bank, Sir Nicholas Stern, and Bob Geldof, who is working with Helius Energy, a British company developing the weed's use.
* Critics say that it does not yield enough fuel to be commercially viable and that farmers are finding it hard to find buyers. They are calling for further research.