'What we are suggesting combines safety and environmental conservation. We want to replace these walls that have disfigured the city with natural hedges that provide insurmountable security,' he says.

Mr Zimmermann is the export manager for Sinnoveg, a 420-hectare nursery in eastern France that specialises in 'natural defensive weaved hedges' - walls made from tightly bound thorny plants.

At the height of Iraq's sectarian fighting US and Iraqi forces erected a vast network of concrete walls, checkpoints and concertina wire that choked off dozens of Baghdad streets and isolated entire neighbourhoods.

As security has improved over the past two years, however, the government has started removing the barriers, and Baghdad's security spokesman said last week that all the capital's streets are to be reopened by the end of the year.

But the walls around government buildings and embassies - most of which are concentrated in the so-called Green Zone in the heart of the city - will remain.

And that is where Mr Zimmermann comes in. Why not, he suggests, make the Green Zone green? 'This is the kind of place where we can provide protection. We can remake Baghdad as a city focused on nature, ecology and the environment, with a new concept of security,' he says.

The principle is simple: plant a row of thorny trees and bushes 80 centimetres apart and weave the branches together. As the plants grow they form a dense and razor-sharp hedge that within three years can reach a height of six metres.

Mr Zimmermann said traditional barbed wire, tyre spikes, sensors and even metal barriers can be placed within the hedges - an invisible back-up layer of security sure to surprise any potential suicide bomber.

'A tank can go through but not a truck,' he says. 'The terrorist will think it is a row of plants but then he will be blocked.' -- AFP