California's olive growers are expanding the land devoted to oil production by about 800 hectares, or 30%, with continued expansion expected to put state production on a par with France by the decade's end.

Long focused on the pitted black table variety, the industry is now investing in high-density plantings, mechanised harvesting and mills to compete with European oils.

Americans consume about 300 million litres of olive oil annually, with only 1% produced locally. Droughts and pressure on subsidies are expected to hike the cost of European imports, and the US Department of Agriculture is expected to stop importers from blending different grades and types of oils but still labelling the product "extra virgin", making local production more competitive.

California's industry has a retail value of about US$85m.