by Otto Muller

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, while in Canterbury areas with lower rainfall are preferred because higher rainfall areas are more likely to have problems with blight.  David McNeill is working on a rather ingenious project to find a solution to the problem of blight.  If he is successful he will have earned the gratitude of walnut growers all over the world because blight is not just a New Zealand problem.

To the question as to who should look at walnut cultivation as a form of land-use, I would suggest that 3 groups would do well to do so.

  1. There are a large number of 10 acre blocks.  In many cases the people have got what they are looking for.  However in many cases the owners find that it is too demanding to look after the great variety of farm activities that they are involved.  In many cases they are very much in the red financially.  Once a walnut orchard is established it does not take too much time to look after it.  There would be very few days that one could not possibly go to play golf or go fishing; seldom is there is something on the walnut orchard that has to be done today that could not wait until tomorrow.  Where there is a concentration of smaller walnut orchards it will not be long before an enterprising kiwi gets himself the necessary machinery to go contract harvesting.  And after the rather long period walnut trees take to come into full production the owners of such a walnut orchard will be pleasantly surprised about the very high returns such an orchard is able to bring in.  Since winter is a quite period on a walnut orchard it would be quite feasible to organise an overseas holiday without neglecting what has to be done over the winter.
  2. A walnut orchard would be a good investment to get a retirement income.  It would be necessary to get started about 15 years before retirement.  But it would be quite feasible to establish a walnut orchard in the country while working in the city and doing the orchard work over weekend, which would generally involve irrigation and watering.  Once the orchard is coming into commercial production it would be a very profitable enterprise that still leaves enough time to do all the things for which there was never enough time during the busy working live.
  3. There is scope for large plantations of walnuts.  The operation can be completely mechanised and as such lends itself to large-scale production.  A large Tasmanian company is establishing a 500 hectare block of intensive walnut orchard.  They budget for a production of 4000 tons of whole nuts, which at present NZ prices and world prices would be worth some millions of dollars a year.  The big problem to many people is the very long period required before the orchard achieves commercial production, which in our country would be some 10 years.  This however is not as big a problem as appears at first.  The young walnut trees occupy only a very small part of the orchard and there is no reason as to why the ground in between cannot be used (inter-planted) for other crops until the young walnut tree starts spreading out and bring a commercial return.  If the proposed orchard is part of a livestock farm there is no need to reduce stock numbers.  The area in walnut trees simply would be used to make hay or silage.  We found that from year seven we could keep our merino sheep in the walnut orchard without any tree protection.  We also found that horses did not do any damage even on very small trees.  We only had one horse that did develop a liking for walnuts which turned out to be a rather expensive way to feed a horse.

We did sell a small piece of land for a flower grower who did grow Asian Lilies between the walnut trees.  The walnut trees kept on producing nuts normally and the lilies did well.  There is no reason one cannot grow a crop of corn, onions or squash and countless other crops until the walnut trees start covering a major part of the ground.  Walnut trees are very deep-rooted and in suitable ground will have roots extending to 5 meters depth.  As such they are not very much affected by shallow rooted crops, provided fertiliser is applied to cover the need for both crops and there is no shortage of irrigation water.  Commercial walnut production is very profitable and there would be very few other crops that would provide a comparable return after costs.  Above all among the horticultural crops there would be very few that involve the low level of hassles you have to contend with on a walnut orchard.

We planted our first walnut trees 17 years ago. They were seedlings and have now a trunk of 250mm diameter.  The next planting was a trial orchard with 11 varieties of walnut trees.
Among the many varieties the Vina was outstanding from every point of view.  I am aware, that Canterbury growers do not find Vina a good nut.  This is probably due to the fact that in our microclimate in the Bannockburn area we have some 1250 Degree-days.  They like the heat.  I found that in the southern district of the San Joachim valley the average yield of the Vina was 7 tons per hectare and these were all young plantations since the variety is a relatively new one.  Unfortunately we had a big fire and lost our entire trial block.  We have now our new plantation along the lake, which is slowly coming into production.  We have a nursery operation with a capacity to plant new blocks at the rate of some 800 grafted trees a year.

We are training our trees to have 2.5 meters clearwood. This does take a few years longer than allowing the lower branches to fruit.  Our reasons are:

  • Keeping the fruiting branches well clear of the ground keeps them away from any ground frost.
  • Keeping the orchard clear of branches hanging down improves air circulation and avoids danger of blight.
  • It is possible to provide frost protection in a nursery, while it is not practical to do so at a field level. So we grow trees to the 2.5 meters in the nursery and transplant them, so avoiding frost damage to our young trees.
  • We can operate all our machinery under the trees without any danger of having our heads chopped off.
  • During our market research we found that the highest price paid for walnut timber was for a tree trunk with a minimum diameter of 65cm at a height of 2.5 meters (standard plywood panels are 2.4m — 1.2m).  Last year prices paid for this grade in Germany was $5-6000 per m3.  One of my friends who has a large furniture factory in Europe has his own plantation.  He grows the trees to 4.5 meters clearwood.  He started the plantation because he could not depend on a regular supply of walnut timber.  In this way at least his son will not have this problem.  We had some visitors from part of the USA where they grow large areas of black walnuts.  They told us that they had to keep armed guards on their plantation for 24 hours a day to guard this valuable timber.  It is important to realise that if we want to play a part in this highly lucrative timber market, we have to be able to regularly supply substantial quantities of a high class of such timber.  I feel that timber grown in the North Island would grow too fast to be acceptable by European furniture manufacturers.

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.  Nick Nelson Parker at Opotiki has varieties doing well in the area, where our selected varieties would most likely be a failure.  I believe that 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.

We have also been busy developing technology to deal with the processing of walnuts.  We built a nutcracker to crack nuts with doing minimum damage to kernels and of very high capacity.  It is based on a different principle to the ones used in the USA and Europe and we got the process patented.

Here in Central Otago I can see the main limitation to the walnut industry in the very high prices paid for land suitable for growing Pinot Noir grapes.  They have the same climatic requirements as our walnuts.

Additional Note:
Regarding the walnut industry, I believe that it is important to realise that it is possible to grow crops in between the walnut trees to utilise the ground until we get a commercial return from the trees.  I believe the long wait for this return is 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 the walnut trees until they start producing commercial yields.  They grow one row of peaches in between each row of walnuts and one peach tree in between each walnut tree in the rows, peaches start producing commercially after 3 years and it is not unusual in our country to plant peaches for a rotation of some 6 — 10 years.  When the walnut trees are staring to cover the ground the peaches are removed.  In economic terms a highly productive walnut orchard would be pretty hard to beat with regard to the net return per hectare.  What impressed me above all was the ease with which such an orchard can be managed and the absence of most of the hassles that go with most other horticultural crops.

Otto Muller