Walnut crop guide

Family – Juglandaceae

Also called ‘Persian’ or ‘English‘ walnut. Regia from the Latin ‘royal’ was probably given because of the delicious flavour of the nuts.

The term “Carpathian Walnut” in its widest sense generally refers to a cold-hardy race of J. regia adapted to northern latitudes from about 35-45°North.
In contrast the French varieties which are much more sensitive to cold are generally known as Persian walnuts.
Walnuts have been imported from overseas over the years for trials here in New Zealand

It can be a tall tree to 30m and 1.5m diameter with a broad rounded crown.
Silvery gray smooth bark when young, becomes furrowed on older trees.
Compound alternate leaves formed of 5-9 leaflets, shiny green on top and light underneath 6-12 cm long with slight perfume. It is one of the latest deciduous trees to come into leaf.

Before you decide which trees to plant it is suggested you have your end product in mind.
Timber or nuts or both?
Do you want to sell nuts in shell, shelled or for oil and other processed products?
These decisions will affect which type of walnut to plant.

Success depends on getting the right cultivar for the local environment and the presence of good pollinator clones. Then there is the debate between grafted and seedling trees.

The two major factors limiting the walnut industry are blight and frost.

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Soils

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Climate

Limiting factors are spring and autumn frosts, extreme summer heat and insufficient winter chilling. A North to Easterly aspect is preferable.

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Shelter

It is essential to shelter the young orchard to enable the tree to be trained to a suitable shape, to maintain higher temperatures for maximum growth, and to assist pollination in the young orchard where pollen may be blown away or catkins blown off the tree. It is highly desirable to have shelter established before planting walnuts.

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Pollination

Walnuts are self-pollinating, but, as maximum pollen shed does not coincide with peak pistillate flowering, to attain maximum yields it is desirable to plant at least two cultivars that will fertilise each other.

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Nuts

The fruit is considered as a true nut as both the outer husk or hull and the nut grow with a sigmoid (crescent-shaped) curve.

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Spacing

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Irrigation

The prevention of moisture stress is desirable. However, over-watering rather than under-watering causes more problems.

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Blight control

Walnut blight (Xanthomonas juglandis) is the only significant disease problem of walnuts in New Zealand.

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Propagation

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Rootstocks

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Fertiliser

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Pruning

Pruning should be done only during summer months when callusing occurs more readily.
If pruned during winter this species bleeds which can lead to the death of the tree.

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Weed control

Better growth in the young orchard is maintained with cultivation and the removal of all weed growth from around the base of tree.

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Pests

In some areas rooks(?) can cause serious financial loss by eating the nuts prior to harvest, and rats will eat nuts left on the ground or in storage.

Harvesting

If nuts are allowed to fall to the ground it is essential to pick them up daily or they will be damaged by mould, and the kernels will darken and spoil rapidly.
The best time to harvest the nuts is when they are at peak quality, which is when the packing tissue, which fills the space between the kernel and the shell, has turned brown. This is generally March/April.
Usually the first harvest is 4-5 years with full production at about 10 years.

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Quality

Quality is the dominant requirement.
The meaning may vary but includes the physical and interior attributes, which vary widely with cultivar.

Physical attributes

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The colour of walnut kernels may range form extra light to amber, due to the time of harvesting, location of the tree in the orchard, and variety.
Dark walnuts are not necessarily of inferior quality as in some countries and industries darker walnuts are prized for their stronger taste, However, locally the darker walnuts are currently used as a second grade product, processed into a baking grade.
Lighter walnuts are preferred for the decoration of tops of cakes and pastries by the baking industry (Walnut marketing Board, 1999).
There are also small markets for coloured varieties, eg white and purple.

Interior Quality Attributes

  • Nutritional contents (eg vitamin and oil composition).

  • Freshness (rancidity).

  • Flavour

  • Aroma

Nutritional studies have shown that walnuts are rich in food value and contain a wide range of vitamins and minerals.

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Planting Seed

Walnut seed loses viability under warm dry storage condition. They should be kept at just above 0°C from harvest until they are planted.
Mid-winter planting with the seedlings emerging in spring seems to be most successful.

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Seedling trees vs Grafted Trees

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Which Type?

There are four basic types of walnut selected for. Numerous varieties have been produced within these types:

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Nut types

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Selections named at NZTCA Conference 1998

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Walnut Descriptions

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Economics of walnut orcharding

There are many variables in estimating what is an economic area to grow. A small area may use a minimum of machinery but a lot of hand labour.

A large area will be dependent on machinery. As yet data is too limited to make an informed estimate as to what is an economic area to grow.

Potential market

With a New Zealand population of 3.89 million and a consumption of 45gm per person (present consumption) = 175,850kg per annum.

At the French level of consumption of 2.5kg per annum = 9,725,000kg per annum.

At the German level of consumption of 4kg per annum = 15,560,000kg per annum.

If good quality nuts were marketed in New Zealand, many of the nuts sold at present would not be sale-able.

The product range now made in New Zealand includes: in-shell walnuts, halves, pieces, chopped, ground, paste, oil, pickles, and other byproducts.

A Christchurch business is processing both cultivar types and seedling nuts and is unable to fill the demand.
The oil is reputed to be the best in the world according to well known Chef Julie Biuso.

There are also markets to be filled in the North Island with shops specialising in locally grown products.

Grafting

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Sources of information:

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Recent significant work

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Original Walnut Fact Sheet, B.J. Vavasour

Updated 1996, Dr David McNeil
Updated 2001, 2007, Gail Newcomb
Privacy removals and proprietory format conversion – December 2007
2015 Post unavailable for a period due to a naming conflict – apologies. Other updates.

This crop guide was produced with the latest information available at the time of publication. This should not be considered the ultimate in information for New Zealand growing conditions: it is just a basic guide on the subject. If any member has information to add, or feels that any of the information is misleading, please use the contact below.

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Comments

Walnut crop guide — 10 Comments

  1. I have 2 walnut trees which I think are approx 40 years old that do not have many leaves, same thing happened last year, they grow side by side. also have 100 year old as well, several others and they all seem to be fine, my property is very wet during winter, do you think they have a disease?, thankyou

  2. Is the Levin Area suitable ?
    The soil seems to be mainly Clay.
    Who is selling plants ?
    What is the average cost ?

  3. I live in Maine, USA. I have 5 seedlings started inside the house. We’re heading into our winter season, so I’ll keep them inside for the winter. When should they be transplanted outside? After the last threat of frost in the spring? Will they survive temperatures below freezing?
    Thank you.

  4. I have 2xhundred year old walnut trees that need to be cut down. I am in Piopio in the King country. Would you have any interest in the timber Thanks Dawn

      • Asking around millers and woodturners – would love some wood but logistics, travel, transport, storage circumstances usually overwhelming. But thanks for your offers.

  5. Hi there, I’m looking for a site to plant a a commercial orchard, South Island, possibly Canterbury near Christchurch, but will consider other locations. Will also consider purchase of operating commercial walnut farm, South Island. If anyone has any contacts or wishes to sell land or farm, please contact me at [contact details supplied, please use ‘get-in-touch’ contact form, subject ‘Commercial Walnut’]. This is a private request, no agents please.

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