NZ Walnut Industry Group

The New Zealand Walnut Industry Group has about 80 members, 85% of whom have orchards within 50kms of the Cracker of a Nut processing plant near Christchurch. The modern NZ industry is based primarily on grafted varieties Meyric and Rex, identified by the Tree Crops Association in the 1980s as the best performers from hundreds of nut samples sent in from around the country. NZWIG chairman Nelson Hubber and his wife Wilma have 900 trees of three varieties (including NZ Purple) on 11ha at West Melton and a nearby orchard owned by Andrew and Jo Horsbrugh has 3600 trees in total of four varieties on 47ha. They have 60% Rex, 40% Meyric and a 100 trees each of NZ Purple and Tehama. Nelson Hubber and Andrew Horsbrugh are well-placed to describe orchard planning, tree planting, tree care, disease prevention and walnut harvesting.

Dry, low-humidity climates are good for walnuts – anywhere grapes are grown successfully. Higher rainfall/humidity tends to bring more blight and other diseases. They need protection from wind and frost when small. Larger trees can cope with minus 10deg when they are without leaves but young shoots, leaves and flowers can be damaged by even light frosts in October and November. They must be grown on free-draining soils because they are subject to phytopthera root rot if the ground gets too wet and stays wet for quite short periods, even for only a few days. The Horsbrughs spent 18 months looking for the right location.

Tree spacing is 10m by 10m, although the Hubbers have 10m by 5m with offset rows, intending to remove every second row when tree canopies begin touching.

Perceived as a long term investment, grafted trees can crop after six or seven years with useful production after 12 years with a potential yield of over 50kg per tree after 30 years.

The Hubber and Horsbrugh orchards were established in 2000-2002 and were expanded every year for a decade as grafted seedlings were available. The Horsbrughs have also transplanted some trees after cutting them right back, using a digger to extract a tree with root zone, a trailer and another digger to plant them. This was in order to free up land for suburban development on the outskirts of expanding Christchurch.

Both orchards use Cropliner air-blast sprayers for copper applications and foliar fertilisers. Copper is applied regularly to combat walnut blight, the only major disease.

They have irrigation systems with sprinklers under the trees and drippers in the shelter belts.

Nelson Hubber has a home-made harvester to pick up fallen nuts with a spikey roller and deliver them into a bin with auger unloading. The Horsbrughs have a French-made, self-propelled harvester, five metres long and weighing three tonnes. The AMB Rousett machine is a sweeper-harvester that collects across 3.0m into a 2m-wide mouth, delivers nuts across a chain drive to bins carried on the back of the machine, that can be lifted and tipped into a trailer and/or conveyor. They also have a tree shaker that is used at the beginning and end of the harvest. A side-chute blower is also used to concentrate blighted nuts and trash so they can be mulched and clear the ground before harvest, which begins in the last week of March and goes for a month.

Both orchards have washing drums and drying sheds for storing nuts for several weeks before delivery to the Cracker of a Nut processing plant nearby.

The older trees on both orchards are now producing larger volumes of nuts and the annual crops are expected to grow exponentially from now on. For example, the Horsbrughs harvested three tonnes last year and expect to get 10 tonnes this year.

NZ fresh walnuts attract a considerable premium over imported products, which tend to be rancid by comparison.