Valda and Otto Muller are taking a serious crack at the organic walnut market. The couple grows several varieties on a 133 hectare plateau above the Kawarau River in Central Otago.
Otto and Valda planted their first tree in 1986 and, over the past 25 years, they have grafted and planted 1300 more.
There have been incidents and accidents along the way though. In 1992 they lost a major a research block to fire. It held 16 different cultivars of North American and European walnuts they were trialling.
Valda says "We were fortunate that although the trunks were well and truly charred and the cambium layer was charred, it actually threw out enough scion wood that we were able to collect that and propagate the trees that are here, on from that wood."
Ninety-three-year-old Otto, who grew up in Switzerland, is an engineer by trade and has custom built several machines in his workshop to reduce labour costs and to aid each step of the harvesting process. One of them is a vibrating machine that helps to release the nuts.
"Basically it's mobile; you drive into the trunk and then wrap an inverted canopy around it so that the nuts will be vibrated off the tree and run down the canopy into a collection bin, so the nuts don't even touch the ground."
He has also made a shelling machine that can process an impressive 300 kilograms of walnuts an hour.
The Muller's sell the walnuts online and at the Otago Farmers market in Dunedin and this year they are expecting a bumper crop.
Walnuts are the oldest tree food known to man, dating back to 7000 BC. Early history indicates that walnuts came from ancient Persia where they were reserved for royalty.