Simon Hedges and truffle dog Jimmy sniff out winter truffles for Sydney fine diners

The kelpie's careful training is put to use just eight weeks each year when black truffles ripen under the oak and hazelnut trees Simon Hedges planted 14 years ago on his family's NSW Central Tablelands property.

Now Jimmy joins his master on a windswept hill with the mercury hovering above zero in early June, sniffing the ground until he detects the distinctive aroma of a prized fungal fruit growing just beneath the soil.

He sits and waits for Mr Hedges to confirm the find and give him his treat.

"He is very good at finding that ripe smell," he says.

"It's good to have that nose ... because you can sit there on your knees and sniff the ground and not smell anything.

"He'll go across and scratch the ground [and find one right away]."

The farm, which has been in Mr Hedges's family for more than a century, sits 1400 metres above sea level on the banks of the Duckmaloi River outside Oberon in NSW.

In winter, locals get snowed in and shut off from the rest of the world. In summer, it rains enough to keep the soil moist for truffle growing. Too much rain can cause dreaded truffle rot.

"It took about eight, nine years before they started showing - and then it was probably the last two or three years that we've got a half decent crop out of them," Mr Hedges says.

Truffles won't grow under any oak or hazelnut tree; they must be specially inoculated with the truffle spore.

Australia's first spore-infused trees were planted in Tasmania nearly 30 years ago and the first truffle harvested at the turn of the millennium, according to the Truffle Industry Association.

Truffle orchards - or truffières - are now dotted across the colder parts of southern Australia.

Among the hundreds of varieties around the world, the most commonly grown is the French black truffle, known as the "black diamond of the kitchen".

The distinctive earthy taste is used in restaurants to flavour dishes from risotto and pasta to scrambled eggs and butter.

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For eight winter weekends each year, Mr Hedges carefully harvests the ripened truffles with Jimmy by his side and painstakingly hand washes them using a soft toothbrush and water.

He has a very small window in which to deliver them to a handful of restaurants in Sydney because, once a ripe truffle hits the open air, it must be consumed within eight to 10 days.

All of this makes truffles very expensive to produce - and buy.

A first class truffle the size of a golf ball weighs about 50 grams and will fetch anywhere between $1.50 and $1.80 per gram, Mr Hedges says.

Even a lesser specimen will go for up to $1.30 per gram.

The truffière at Duckmaloi River Truffles produces between 10 to 12 kilograms of saleable produce each winter.

And Mr Hedges loves the work.

"Finding them is good and finding a ripe one - perfectly nice, round and beautiful looking truffles - is good," he says.

But creating the perfect dish with his harvest?

"I'm a very bad cook," he says.

"Cooking with them is hard - that's not my gig."