These cultivars don’t need cool winters to trigger their natural flowering.

Graham and Annemarie Brookman run The Food Forest, a 15ha property near Gawler. Geographically speaking, it isn’t big, but its ratio of produce to hectare is one of the state’s best.

The Brookmans grow more than 150 varieties of fruit and nuts, including 25 olive cultivars, 20 varieties of pear and 60 varieties of apple, one of which dates back to the period of Roman occupation of England.

But Mr Brookman said that in his 23 years of running The Food Forest, the seasons have become increasingly disastrous.

“In the Northern Adelaide plains, sodium chloride (salt) has built up over the years, to what are now pretty worrying levels.”

Normally the salt, built up over summer, washes away in winter rains.

“But with the years becoming dryer we aren’t seeing that flushing,” he said. “It’s quite scary.”

Mr Brookman said that should climate trends continue, Adelaide farmers would struggle with conventional agriculture, and Australia needs to “ramp up” its importation of new fruit species.

“We need to get new varieties of fruit and nuts though quarantine that can combat the changing climate,” he said. “At the moment it’s very expensive, but we need to start switching to ‘low chill’ varieties sooner rather than later.”

“Low chill” varieties of fruit trees and nuts, such as olive trees, pomegranates and Chinese dates, don’t require a big shift in seasonal temperature in order to bare fruit.

The Brookmans have already begun converting their pistachio crop to a low-chill variety of the nut, native to Tunisia in the Mediterranean.