Walnuts (Juglans regia)How well established is this crop?
This crop is relatively new. It has been grown commercially for approximately 10 years. Commercial returns, current growers and some level of regional based research may be available to help those new to this industry.Background
Walnuts come from a family containing approximately 60 different species all of which are nut producing. The most well known, largest and most easily cracked is the nut we call the Walnut (Juglans regia). It is more correctly known as the Persian or English walnut.
This species is native to the Carpathian Mountains, in Central Asia. It was brought through to Europe through Persia many centuries ago and has become ingrained in many cultures since then.
One of the largest areas of walnuts in the world is in the Central Valley of California. This is the classic Mediterranean climate, warm summers and cool winters.Winter Chilling and Frosts
Long periods of chilling are required to ensure fruitfulness and reliable walnut yields. Chilling requirements vary from species to species and published figures vary from 400-1600hr below 7°C.
A major limiting factor with walnuts in the southern regions of New Zealand is frost. This can kill young trees if it is severe enough and can have serious affects on the crop of more mature trees. Selecting sites with less frosts is desirable.
A combination of regular rainfall/irrigation is required to maintain soil moisture levels and ensure regular cropping.Wind
Walnuts grow into a large tree so shelter from the wind is difficult to achieve. Some shelter around newly planted trees would be beneficial especially on a windy site. Once mature they self shelter.Soil
Walnuts require a deep well drained sandy loam as they have very deep roots (3-4m in some cases!). They do not like restrictive layers as you go through the soil profile. Walnuts do not like prolonged periods of wet soil conditions and are intolerant of soil salinity.Fertility
Fertile soils are considered essential for profitable commercial production. A neutral to slightly acid soil (pH of about 6) is suitable.Weed Control
Weed control under trees is essential to allow nut pickup. Grass in the rows is usually mowed. Be very careful if you are thinking of grazing between the trees. Sheep will and do eat the bark from around a walnut tree. This kills the tree by ring-barking it.
Contact the local branch of Tree Crops Association for information related to your areaPests and Diseases
Walnuts seem relatively free of insect pests and diseases.Layout
10 x 10m is considered the usual layout for a walnut block. The tree gets very large and closer spacing will mean overcrowding. Early intensive plantings at 4.5m apart have now been thinned out to this larger spacing.General Management
All Walnuts are monoecious. This means that they have separate male and female flowers on the same tree. However this can cause problems as in many cases the female flowers are not open when the male flowers are releasing pollen. This means that pollinator trees are recommended to ensure a regular crop.Harvest
Because most plantings are on a reasonably small scale, nuts are harvested from the ground manually or by using a small sweeping device.Equipment
Only simple equipment is required for small plantings including a mower and weed sprayer. Larger plantations may require a higher level of mechanisation.Returns
Unknown at the time of writingContacts
If you are thinking of growing Walnuts, contact your local branch of the New Zealand Tree Crops Association for the addresses of growers in your area. www.treecroppers.org.nz