Saffron cultivation needs lots of land and a lot of labour, but the world's most expensive spice might be an economic lifeline for Afghanistan with international financial support set to fall in the coming years.

In the western province of Herat, elderly women and young girls make their way slowly through a field of tiny saffron plants, carefully plucking the valuable flowers from the soil.

Each plant is placed in a plastic basket, which is weighed on electronic scales.

Labourers then prise apart the delicate lilac leaves, vivid red stigmas and pale yellow stamens -- a painstaking task that demands concentration and skill.

Saffron spice is prized around the world in cooking, in perfumes, as a fabric dye and as a treasured component of traditional medicine.

A few slithers of red saffron stigma also make a colourful and aromatic tea reputed to have near-magical healing qualities.

As such, saffron should be the perfect crop to boost Afghanistan's fragile economy and provide an alternative to the poppy harvest that produces illegal opium and funds Taliban insurgents.

But it is not a simple solution: costs are high, a harsh winter can wipe out the crop, and neighbouring Iran dominates the market - producing about 90 percent of the world's saffron.

In Herat, about 6,000 people - 4,000 of them women - are employed in saffron farming on 800 acres (325 hectares) of land, with the product exported to India, Europe, the United States and China.

Since the fall of the Taliban regime in 2001, all US-led efforts to eradicate poppy production have failed dramatically, with cultivation reaching a record high in 2014.