The vegetable alternative to airport sniffer dogs was produced by embedding the plant’s leaves with tiny chemical sensors.
When the spinach sucks up ground water tainted by explosive, it primes itself to send out a light signal that can be read by an infra-red camera one metre away.
The signal is switched on by shining a laser onto the leaves.
The research is said to be one of the first demonstrations of “plant nanobionics” - the wedding together of plant biology and electronics.
Lead researcher Professor Michael Strano, from the Massachusetts Institute of Technology (MIT) in the US, said: “The goal of plant nanobionics is to introduce nanoparticles into the plant to give it non-native functions.
“Plants are very good analytical chemists. They have an extensive root network in the soil, are constantly sampling ground water, and have a way to self-power the transport of that water up into the leaves.”
Prof Strano pointed out that the spinach signals could easily be read by an adapted mobile phone camera.
“This is a novel demonstration of how we have overcome the plant/human communication barrier,” he added.
The plant sensors consist of microscopic carbon nanotubes - tiny hollow carbon rods - designed to detect nitroaromatic compounds, chemicals widely used in land mines and other explosive devices.
The MIT team has previously developed carbon nanotubes sensitive to the bomb-making ingredient hydrogen peroxide, TNT explosive and the nerve gas sarin.
Two years ago Prof Strano used nanoparticles to create pollution-monitoring versions of the lab plant Arabidopsis that could detect the combustion chemical nitric oxide.
The new research is reported in the journal Nature Materials.