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.
In Central Otago the area suitable for planting is limited to areas frost-free during the growing season of walnuts.
In Canterbury areas with lower rainfall are preferred because higher rainfall areas are more likely to have problems with blight.
David NcNeil is working on a rather ingenious project to find a solution to the problem of blight and if he is successful he will have earned the gratitude of walnut growers all over the world as it is not just a New Zealand problem. It is quite possible that some varieties of walnuts growing in areas which are generally not considered to be suitable for commercial walnut production could very well have resistance against blight. It is possible that this genetic plant material could be important to increase the areas where walnuts can be considered a commercial crop, since they are likely to be resistant to blight.

It is important to realise that it is possible to grow crops in between the walnut trees to utilise the ground until there is a commercial return from the walnuts. The long wait for this return could be putting many people off the idea to grow walnuts commercially.
In countries in the Balkan it is a usual practice to grow peaches in between each row of walnuts and one peach tree in between each walnut tree in the row. Peaches start producing commercially after 3 years and it is not unusual to plant peaches for a rotation of 6-10 years. When the walnut trees are starting to cover the ground the peaches are removed.
There are many other horticultural crops that can be grown in this manner.i

J. regia is the only species suitable for commercial nut production. For commercial production it is suggested to use cultivars approved by the Walnut Action Group of NZTCA.

The drier areas of the eastern parts of New Zealand are suitable for commercial nut production.
Many other areas are suitable for timber and home orchards, provided 4 metres of free-draining soils are available.

Walnuts are suitable as an organic crop and there is an established market in Christchurch for them; named cultivars as well as ‘wild’.

Soils

All walnuts, regardless of variety, require a fertile, free draining soil.
The roots have to breathe. If a soil is waterlogged there is no oxygen for the roots.
It takes only one day of waterlogging to kill a walnut tree and even soaking for too long before planting can have the same effect, as does constant leaking water.

Soil should be neither too acid or too alkaline.

There is evidence that walnut trees improve the quality and quantity of pasture beneath them but some plants will not thrive if they come into contact with juglone from the roots.

Indicator crops, which may show where walnuts will do well, are potatoes and lucerne.

Climate

Limiting factors are spring and autumn frosts, extreme summer heat and insufficient winter chilling. A North to Easterly aspect is preferable.
Late spring frosts can damage catkins, new growth and young fruit thus spoiling nut set, but unless severe they are not normally a problem in older trees. In colder areas selection of late-flowering cultivars is important.

Early autumn frosts can injure young shoots preventing leaves the following spring. Winter temperatures rarely injure dormant trees.

Winter chilling requirements needed to be considered for different cultivars to break dormancy.
If the cultivar does not have adequate chilling, they leaf out and bloom late. Nuts are then small and crop reduced.

High summer rainfall can cause blight (Xanthomonas juglandis), as it thrives under moist humid conditions. Progress is being made with blight resistant cultivars.

Growing walnuts in areas of low summer rainfall, preferably less than 700 mm per annum to lessen the problems associated with blight is best for nut production. (See later under Blight Control.) The additional water requirements may then be met from under-tree irrigation.

Nuts grow rapidly during the 5-6 weeks immediately after flowering. Shortage of moisture during this period results in a large percentage of small size nuts.
No amount of mid-summer (or after) irrigation will increase the nut size once the shell has hardened.

Sunburn early in the season may cause “blanks” (no kernels); later the kernels may be partly shriveled, dark or stick to the shell and stain.

Wet weather at harvest time will cause stained kernels and shells and may delay nut fall from husk.

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.

You need permanent shelter on the outside of the orchard, as well as temporary, fast growing shelter internally that can be removed later.
Excessive shelter will produce leggy growth that will not stand strong winds.
Remember that any shading of the walnut tree will reduce the nut yields.
Select the right type of shelter tree as they can suffer from competition from some, which are too dense, casting shade and robbing the soil of nutrients and moisture.

Blackened edges of the leaves are a sign that they are being physically damaged by wind.
It is much more difficult to see the more serious damage of the tree being cooled by the wind.
Walnuts grow best at temperatures between 25-49°C so shelter greatly improves cropping and growth.

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.
For information on compatible cultivars contact the Walnut Action Group.
In all situations some mixture of trees may be required for adequate pollination.
The exact timing of pollen-to-flower formation may vary in different sites for different lines, so that several lines would be recommended.
The highest quality nuts are not always the highest yielders and growers should decide which is the more important to them.

Male and female flowers are present on the same tree.
Male flowers are clusters of small brownish green hanging catkins (with pollen) carried on one-year-old twigs.
Female flowers are very small, green and insignificant in groups of 1-4 at the end of young shoots of the current season, laterally in some new cultivars and appear in late spring (mid October).

The main difficulty with walnut pollination is the failure of pollen shedding to coincide with the receptiveness of the pistil. In some cultivars pollen is released too early and in others too late for pollination of the majority of the pistillate flowers.
Accordingly in any planting plan provision should be made for cross-pollination by planting different combinations.
Basically the aim is to combine an early pollen shedder with a late on, so that pollen is available during the whole of the pistil receptivity period for both cultivars.

Pollen is normally released 10-12 days after bud burst with full bloom of female flowers usually 15-18 days later though this varies between cultivars.

The pollen is distributed by wind and in a dense orchard its maximum effective movement is about 80-100 metres.

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.
The edible kernel varies as to colour and taste depending on cultivar.
Harvest time is March to April when the hulls turn brown.
Some cultivars release nuts from hulls on the tree, others are removed mechanically.
Irrigating a week before harvest can make nuts drop.

If using for pickles pick about December, before the nut has hardened and a needle can be pushed through.

Spacing

In the commercial orchard, spacing at 11m by 11m is suitable where sprinkler irrigation is used to cover the total orchard area.
Where trees are liable to grow very large without cutting back a spacing of 15m by 15m is desirable, with interplants for heavier production in the early years.

Some of the newer lines (eg Vina) are much smaller trees than traditional varieties. With these, a 6m x 6m spacing, eventually becoming 12m x 12m spacing would be most suitable.

With the use of mini-sprinklers for irrigation, or where no irrigation is used, spacing may vary. The important point is that trees do not shade each other nor branches inter-twine.

Irrigation

The prevention of moisture stress is desirable. However, over-watering rather than under-watering causes more problems.
The result of over-watering is root damage and dieback in the tree, which, if severe, can be righted only by severely cutting back the top of the tree to compensate.
When irrigating, the use of tensiometers at a depth of 1.5m is a simple precaution to take against over-watering.
Commercial irrigation monitoring with neutron moisture meters has also been successfully used in some orchards.

Blight control

Walnut blight (Xanthomonas juglandis) is the only significant disease problem of walnuts in New Zealand.
Blight is controlled by the use of copper-based sprays such as Bordeaux mixture or Kocide 101.
With a mixture of cultivars, spraying will need to be done at 10-14 day intervals from catkin development through to pistillate flowering.
If heavy rain follows spraying, the spray may need to be applied again, although light rain will reactivate the spray.

Propagation

Propagation is by either grafted or seedling trees depending on the end use.
Patch, chip or tee budding is used in various nurseries.
Seedlings are much more vigorous and some lines come fairly true to type. (See section Seedlings v Grafted).

It is possible to provide frost protection in a nursery while it is not practical to do so at a field level. Grow trees to the required height then transplant, to avoid frost damage.

Rootstocks

Juglans regia (English Walnut): Suitable for use as rootstock. As the Action Group has as yet done no satisfactory trials on rootstock you have to select your own – use fast-growing seedlings. It is more tolerant of medium fertility soils than J. nigra

Juglans hindsii (Californian Black Walnut): An excellent rootstock for very free-draining soils. Seed may be available through the Walnut Action Group.

Juglans nigra (Black Walnut); If this variety is used as a rootstock, it may produce slightly less vigorous trees. However, it is susceptible to black line disease, which can rapidly kill a mature tree. This disease is not yet a problem in New Zealand, but using this as a rootstock may increase the risk.
In some areas it is considered as too fast growing – incompatibility does not show up for some years and is disastrous if the trees are just coming into full production. Where there are clay soils which are prone to water logging J. nigra is a preferred rootstock as J. regia tend to get die back. (Eric Cairns)

Juglans ailantifolia (Japanese Walnut): Not suitable for rootstock.

Juglans neotropica (Andean Walnut): Has been used in Bay of Plenty.

Fertiliser

Soils should be kept at pH 6 to 6.5.
Nitrogen is necessary for plant growth and will be especially needed by young trees in the first years of establishment.
A good balanced NPK fertiliser, such as those used for apple or kiwifruit orchards, would be a reasonable annual base fertiliser, with a nitrogen side dressing in the establishment years.

Soil tests should be used to help you decide what fertilisers are needed.
Foliage tests should be carried out if you suspect any deficiencies, especially of minor elements.

There should be a good balance of soil nutrients.
Foliar analysis has shown why the addition of more nitrogen gave no response for a BOP grower. It was because the Magnesium levels dropped as a result of the extra Nitrogen, resulting in the tree being unable to use that extra fertiliser.

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.

In New Zealand a minimum of pruning is required.
Pruning needs to be done only to correct faults and to make the tree into a strong shape so it will withstand wind and mechanical shaking for harvesting.
For air circulation, no branches should be below 1.5m from the ground on the mature tree.
The first limb, being the strongest, should be into the prevailing wind.
Branches opposite each other sap the energy from the central leader, and one should be removed.

Any limbs growing excessively should be cut back to two thirds the height of the central leader from the base of the branch.
It is desirable to try and space the limbs well apart in a spiral around the tree.
Alternatively, trees may be pruned to the vase shape, which may have the advantage of letting more light into the centre of the tree and consequently giving an improved fruit set. This method is not recommended for Canterbury, where limb breakage is common with trees pruned to this system.

For timber and nuts, trees are trained to have 2.5 meters clearwood. This does take a few years longer than allowing the branches to fruit, but has the advantages of keeping fruiting branches well clear of ground frost. The orchard is then clear of hanging branches, which improves air circulation and lessens the likelihood of blight.

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.

However, this is expensive in equipment and labour, so sprays may be used to keep weed growth at least 2m from the base of the tree. This is particularly important on dry soils.
As walnuts have deep roots, most pre-emergent weed killers can be applied to bare ground to prevent weed growth. Gardoprim, Simazine, Surflan and Caragard have all been used, but care should be taken on very light soils with Caragard. Surflan is a better choice for sandy soils.
Roundup and Paraquat can be added to any of these pre-emergent chemicals to kill existing weeds. Fusilade, Goal, Karmex, Touchdown and Treflan are also suitable for walnuts.

Word of warning: Roundup will damage young trees even if it gets on dormant bark, so that care must be taken to protect the trees from spray contact.
Also, none of the chemicals mentioned is at present registered for use with walnuts, so care and consideration must be taken prior to their use.

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.

This generally coincides with the green hull covering the nut starting to crack and break away, at which stage about 80% of the nuts will fall with the first good shaking.

For the commercial orchardist, nuts may be gathered by hand or mechanically.
The amount of machinery used will depend on the size of the orchard, but may consist of shaker, sweeper, pick-up, huller and washer, drying and storage facilities.
On a small scale, walnuts can be air-dried in open mesh sacks or on wire racks.

Quality

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

Physical attributes

  • Kernel to total weight ratio (crack-out percentage) should be at least 50%

  • Strength of sealed shell – a thin shell may give a better crack-out, but if too thin it will break in the field at harvest. A poor seal will let in codling moth and mould.

  • Colour of kernel – the market demand is for a light, attractive colour (McNeil et al, 1994)

  • Nut size – larger nuts are sought for the in-shell trade.

  • Nut shape – should be appealing to the eye and may be important with respect to ease of extraction from the shell and breakage during mechanical shelling.

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.
They contains about 70% oil, which is primarily polyunsaturated, and are rich in essential fatty acids which are essential to health through their cholesterol – lowering benefits (Chisholm et al. 1998).
Other benefits come from their high content of fibre, vitamin E, arginine, antioxidants, some minerals and their level of protein (about 14.1 grams per 100 grams of edible nuts, most of which is digestible).
However it is the polyunsaturated fatty acids which if not stabilised (eg by vitamin E), may cause walnuts to become rancid, consequently reducing their shelf like.
New Zealand cultivars tend to have more variable fatty acid and vitamin E profiles than locally grown or imported European and American walnuts. (Savage, McNeil, Dutta, 1998)

Local consumer preferences lean towards larger sized walnuts with light coloured kernels (Johnson, 1993) even though very large walnut generally suffer from a lower kernel crack-out and light coloured walnuts are often weaker in taste.
Other preferences are toward sweeter nuts with a lack of aftertaste (McNeil, Smith Gardner, 1994).
Shelled walnuts are highly susceptible to deterioration through moisture, light, heat, and oxidation in air causing losses in freshness and taste besides promoting kernel darkening leading to rancidity with reduced shelf life. Similarly walnut oils have been shown to be unstable when heated (40°C) or subjected to air or sunlight for prolonged periods.
Imported walnuts are often inferior, being shelled walnuts stored for long periods in unfavorable conditions. So the local industry has concentrated on the selection of high quality walnut cultivars.
However good quality nuts can easily be spoiled during the harvesting and post-harvest operations.

Southern Nut Growers Association promoted NZ grown nuts as a high quality product, and to this end they have set up various quality standards which must be met before nuts can be sold under the Southern Nut logo.ii

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.

Stratifying seeds just above freezing point for two months or more before planting can improve germination.
Nuts should be planted in the nursery at intervals of about 30cm, about 5cm deep, and in rows 2 meters apart.

The best planting position for walnut is horizontal with the plane of the suture line perpendicular to the soil surface. From this position when the nut germinates, and the tip of the shell opens, both the root and the stem emerge readily and produce the strongest, most rapidly growing seedling.iii

Seedling trees vs Grafted Trees

Point of View 1 – Nick Nelson Parker

There is a huge range of quality factors that make the nuts more usable, not the least of which is size.
Considering the cost of fertilising and protecting a walnut tree until it starts cropping, it is worth taking the extra trouble to plant a good variety.
There is a report of a someone who planted a walnut tree they found on the side of the road, then waited twelve years to find out that it was not even a proper walnut, but a wild Japanese species, only useful for fire lighters.

The most important factor in the time taken for a new walnut tree to come into bearing is not breeding at all, but how well the tree is looked after in its formative years. On Nick Nelson Parker’s orchard he has come up with a planting method that took five years off this waiting time.
However, a grafted tree will produce male flowers up to ten years before a seedling.
If you have planted some walnuts seedlings where there are no other older walnuts trees to provide pollen, then you could be waiting a while for some nuts. Strangely enough seedlings produce female flowers at the same age or earlier than grafted trees. If there are male flowers around they will produce nuts. The youngest he has had nuts off a seedling is eighteen months after planting.

A popular misconception is that walnuts do not come true from seed. They have planted about 2000 seedling walnuts and can say that they grow quite satisfactorily from seed. There obviously is some variation, though not marked. The important thing to remember is that the tree providing the male pollen has as much effect on nut quality as the one the nut came from. That makes it important to know both parents.
When planting a grafted tree, only the one the graft came from is important.

Like most biological decisions it is a numbers game. The result is that if you are planting less than 3 walnut trees, it pays to plant a grafted tree.
If you are planting more than 10 trees it pays to plant one grafted tree for pollination, and the rest seedlings, provided that both parents are as good as the grafted ones available.iv

Point of View 2 – Otto Mueller

Another grower reports that when there has been a shortage of grafted walnut trees, a number of people planted seedlings.
During a conference for walnut producers from all over the world in Budapest, there was general consensus that under good management it was possible to get the following production from a mature orchard:

Seedling trees: 2.5 tonnes/hectare

Terminal bearers: 4.0 t/ha

Lateral bearers: 6.0 t/ha

Seedling nuts in the South Island sell for a lot less than grafted, so the return for grafted lateral bearers would produce the best return.
It was pointed out that lateral bearers will only produce more than the terminal if the trees are subject to a suitable pruning regime to enable light to penetrate into the centre of the tree.
There is also a great yield variation among different varieties. On some of the good nuts they got 80% whole nut halves but the poor nuts from the seedling orchard would have been more profitable to crush for bird feed.

In the best markets for walnuts, the undamaged nut half is worth twice the price of broken pieces. From the processor’s viewpoint the price they can afford to pay producers is based on:

  • The percentage nut-halves and quarters they can obtain, and the amount of time to do the hand sorting after the cracked nuts have been through the separator. Separation of shell-pieces and kernels are generally done by the air-stream separator:
    It is very effective in separating the plump kernel from a thin shell.
    It is ineffective in separating a skinny kernel from a fat shell.

  • The effective crack-out percentage. If nut-halves are stuck in the half shell it may be more economical to deed them to birds than to extract them by hand.
    It is reasonable to expect that the processor may not be interested in buying seedling nuts if the recovery of sale-able pieces is poor and takes too much hand sorting.

  • Uniformity is of the utmost importance so that machine settings can be made for a given variety. Seedling trees where every tree differs are not attractive to a processor.

It is also of interest to find out the reason why seedling trees are less productive. One major reason is “pistillate flower abscission”. Many seedling trees produce an enormous amount of male flowers. Scientists have now established that excess pollination causes a build-up of ethylene, which results in the pollinated female flowers falling off. Trees among these heavy pollen producers produce hardly any nuts at all, although they are healthy and full of female flowers.

Fortunately our grafted trees have their female flowers at a later time and are not affected. Also, seedling trees that have their female blossoms at a different time to the heavy male blossom producers have good crops though of inferior quality nuts.

The question of uniformity of products is of equal importance with regard to walnut timber. We can only play the world market if we can regularly export substantial quantities of walnut timber.
The variety Franquette has a reputation of producing very high quality timber. An American timber company heard of these trees and said they would contact them again in 50 years time with a view to buying these trunks from us.v

Which Type?

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

  1. A high proportion of meat in the walnut and not so much shell.

    Most of the commercial varieties come into this category. Most of these are susceptible to blight. The Californian varieties are particularly bad for this and should only be grown in dry areas such as Gisborne, Hawke’s Bay and Canterbury.

  2. Easy walnuts to open. These are usually extra large nuts as well.

    Although all walnut varieties have been selected for size of nut to some extent, the easy to open varieties tend to be extra large. The best know in NZ is Wilson’s Wonder type.
    Most commercial growers shun them because they tend to have less meat in the shell and are also lighter croppers.
    For the home orchard, ease of opening is a more important consideration. There have been some selections made.

  3. Late leafing varieties.

    Late leafing is a very desirable characteristic if spring and early frosts are a problem. Walnut trees are really designed to withstand frost during winter without any trouble, as it is deciduous. The leaves on the other hand are very frost tender, and frost during the summer can kill a tree if they happen repeatedly. It does not do the flowers any good either.
    There is a German variety G26 which comes into leaf very late. Some years it can be mid-December before any sign of leaf show.
    Franquette, a Californian variety is also late. It comes into leaf early November and also seems to be not quite as susceptible to blight as other Californian varieties.

  4. Varieties that are less susceptible to blight.

    Resistance to blight is an elusive characteristic.
    Walnut blight is increased by rain during spring and summer.
    The ideal is one heavy downpour once a month, at night.
    There is a marked range of susceptibilities, but no variety can be called truly resistant. Even with spray programs some total crop failures are to be expected.

Nut types

The Walnut Action Group of NZTCA has approved a number of cultivars of Juglans regia for use throughout New Zealand. Some nurseries are producing these and selling them with NZTCA Walnut Action Group labels attached. These labels are your only guarantee of type and cultivar.

Cultivars at present fall into three main groups: in-shell, kernel and specialist types.

In-shell types

These need clean large shells with a tight seal but with a kernel that can be extracted easily. Nuts need a high proportion of kernel to shell, nuts should be light in colour, plump in appearance and have good taste.

The trees which grow the nuts should be compact, high yielding, precocious and manageable in the orchard.
They need good branch angles and should not be affected by local frosts, nor subject to diseases such as blight.
Cultivars which seem to meet these goals are G120 and Esterhazy.

Kernel types

Trees for the kernel trade should have all the characteristics of the in-shell types; nut size is generally smaller, the shell seal should be tighter, and the percentage of kernel is more important.
Nuts that meet these goals are W152/Rex, Vina, Serr, Tehama, BLE300/Stan and 1199/Meyric.
(W143/Dublin’s Glory may have some problems with late frosts.)

Specialist nuts

These include Wilson’s Wonder types, very large nuts but with very poor kernel yields, more for decoration in the shell. G1(2)39 also has a purple nut for decoration purposes. Yields are low and shell integrity may be poor. There are instances of growers who are able to sell these types of nuts on a small scale.

Meyric (1199) and Stan (BLE300) are more vigorous trees for use in wide-spaced orchards, such as where timber is also being considered.
G026 is very late leafing out, but may be of interest where the growing season is short. However, a suitable pollinator may be hard to find.

Walnut cultivars are often district-specific, with W152/Stan and 1199/Meyric being favoured in Canterbury, Serr favoured by Bernard Vavasour in Marlborough, and 1199/Meyric performing well in Hawkes Bay.
Franquette and Vina (they like heat) do well in parts of Otago for Otto Mueller.
There is a growing realisation that different cultivars are needed for the North and South Islands.

Selections named at NZTCA Conference 1998

After extensive trials four excellent cultivars have been named.
Local selections have been called Rex, Meyric, Dublin’s Glory and Stan and principally pay a tribute to those who worked on their development.
Meyric and Dublin’s Glory bear heavy yields of high quality nuts, and when you add qualities such as easy opening and improved storage potential, they stand out as good income earners.
Stan Orchard of Marlborough gained praise for harvesting the crop of what was a stunted old walnut on his property and now, through budding and grafting, the progeny is growing throughout New Zealand. Rex – named after Rex Baker – has exciting prospects because it is an easy tree to manage, is blight resistant, and has health qualities, which aid in lowering cholesterol.

Walnut Descriptions

  • Dublins’ Glory (NZ) – Released 1997. Selected for areas subject to late frosts as later leafing and flowering. Heavy yields of high quality nuts. Easy opening.

  • Esterhazy (G) – Moderately vigorous. Thin-shelled medium sized nuts.

  • Franquette (F-USA) – Vigorous, spreading. Terminal bearing, thick-shelled medium sized nuts. Good flavour. Late leafing so needs another late variety as pollinator – perhaps Rex or Meyric. Some blight resistance. High quality timber.

  • Hartley (F-USA) – Medium to large tree Large well sealed nuts with light coloured kernels and good flavour. Late leafing – needs late pollinator.

  • Meyric (NZ) – Released 1997. Not vigorous. Selected for areas with late frosts. Late leafing and flowering, early dormancy. Large, thin-shelled nut, very good kernel quality. Good resistance to blight.

  • Payne (USA) – Medium size tree. Lateral bearing so can be pruned, but susceptible to sunburn. Early leafing so not suitable frosty or humid areas.

  • Rex (NZ) – Released 1997. Vigorous and productive. Selected for late frost areas as it is late leafing and flowering. Small round nuts. Pale kernel. Suitable for mechanical cracking. Blight resistant. Health qualities – lowers cholesterol.

  • Serr (USA) – Vigorous large tree. Lateral buds. Early leafing. Thin strong shell with good kernel.

  • Stan (NZ) – Released 1997. Late leafing and flowering. Long smooth dark shell, light coloured kernel. Less vigorous and slower into production than Serr or Tehama.

  • Tehama (USA) – Large tree, needs pruning to prevent over-bearing. Lateral buds. Medium sized nut.

  • Vina (USA) – Small to medium tree. Heavy cropper of thin pointed nuts. Flat dark kernel.

  • Wilsons Wonder (NZ) – Local selections are available. Good yields. Large nuts. Generally in-shell trade.

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

Patch Budding

Seed may be sown in the final position in the field and later patch-budded, or grown in the nursery and either patch-budded there, or lifted and grafted under controlled conditions.

Patch budding is done with a double-bladed knife with blades 4-cm apart.
Well-grown two-year-old wood is required for buds.
Maximum sap flow is required at the time of the year when temperatures will not fall below 20°C for more than 24 hours during the 10 days following budding, usually the second week of December to the first week in January.

Bench Grafting

Bench grafting is by far the most common method used in New Zealand.
With this method we are dependent on minimum sap flow and maintaining high temperature at the graft union until the graft has taken.
The stock trees are lifted from the nursery, grafted on the workbench, then placed in a Lagerstedt Tube or Lincoln Box for temperature control.

The Lagerstedt Tube

[a better quality diagram please anyone?]

Sketch of Lagerstedt Tube

The Lagerstedt Tube consists of a 75mm PVC pipe with 20mm slits cut into it for its entire length.
Inside this pipe is placed a 25mm pipe filled with water and with heating cable of electrically-safe commercial nursery electric heater attached, with thermostat set to 26°C.
The completed tube can be set up in any convenient shed.
The tube needs to rest on insulation such as roof batts, and have strips of insulation to cover the slits after placing the grafts in them.
Cover the roots with damp sawdust.
The tube can be used for grafting walnuts, hazels, chestnuts, conifers or any other plant that benefits from heat to assist callusing.

The Lincoln Box

As an alternative to the Lagerstedt Tube, a polystyrene box or tube can be used. It has an upper and lower half and the grafted plant is sandwiched between the halves.
The box contains a thermostat, element and thermal sink. A closed foam strip around the box helps contain the heat.
For further details contact Brian E Smith, Plant Sciences Department, Lincoln University, Canterbury.

Sources of information:

Further reading and information was available from Walnut Action Groups.
Walnut Research Group; (NI) Vernon Harrison, (SI) Linda Gardner.
David Murdoch
Dr David McNeil

i: Otto Muller, Personal Notes

ii: DL McNeil and D Waitzmann, Overview of the NZ
Walnut Market,
The Tree Cropper, Issue 22 Summer 1999

iii: DH Ryde, Horticultural Produce and Practice.
Walnuts MAF Publication

iv: Nick Nelson Parker, Personal Notes

v: Otto Mueller, The Seedling Walnut. The Tree Cropper Issue 22 Summer 1999

Eric Cairns, Media release, NZTCA – Walnuts Another potential Earner, March 1998

David Jackson,Temperate and Subtropical Fruit Production, Walnuts

www.naturalhub.com Walnut Varieties (very dated)

Pollock & Halliwell, A guide to Walnut Growing in NZ MAF

Nick Nelson Parker, Selecting a Walnut Variety, The Tree Cropper, Issue 17, September 1998

BJ Vavasour, 1998 Letter to Editor, Rural News.

Recent significant work

Walnut New Varieties Trial, Diana Loader, October 2007, “Nuts’n May”, Wanganui.
Oops, not yet compatible as I strive to convert our heritage ‘user-friendly’, and unlikely to be achieved as I feel the stab between my shoulder-blades from the far right plunderers… surprise, even WordPress is not UF enough for their agenda? Web ed, 6 July 2013

 

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
2013 Post unavailable for a period due to a naming conflict – apologies

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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