CHESTNUTS
WORLDWIDE AND IN NEW ZEALAND

A brief introductory paper prepared by the New Zealand Chestnut Council, 2000

INTRODUCTION

The chestnut is probably the most important nut crop found throughout the temperate zone, worldwide. With species indigenous to all three continents the chestnut has long been cultivated and consumed throughout Asia, Europe and America.

chestnuts in bowlIn the Mediterranean region, chestnuts have been cultivated for at least 3,000 years. The ancient Greeks are thought to have been among the first to cultivate the chestnut, introducing the European chestnut (Castanea sativa) from Asia minor, via Turkey, to S. Europe and N. Africa. The Romans were later responsible for extending the cultivation of C. sativa into northwest and central Europe and it was the Romans who named chestnuts "Castanea", possibly after the name of the town where chestnuts were once very common. It is thought that the word chestnut is an English corruption of the original Latin. In Asia, the Japanese chestnut (C. crenata) has been cultivated at least since the 11th century, and the Chinese chestnut (C. mollissima) possibly for 2-6,000 years. In the US, the American chestnut (C. dentata) was once a major component of the indigenous forests.

Chestnuts were first introduced to New Zealand by some of the earliest European settlers. Today you can still find old, often forgotten trees scattered throughout much of New Zealand, often in the most unexpected places. Most are C. sativa or C. crenata, or seedling hybrids of the two. There are very few named, overseas chestnut cultivars to be found in New Zealand as necessarily strict quarantine requirements make the importing of overseas material extremely difficult, so as to avoid the risk of introducing overseas pests and diseases (such as chestnut blight and gall wasp) which would not only destroy our chestnut industry but could also attack some of our own fruit and tree species.

Plant Type: Small to large deciduous trees - meaning that the trees loose their leaves and become dormant to withstand cold winters. The large edible seeds are called chestnuts and are produced annually on the tree inside a prickly case called a burr. In the autumn, when ripe, the burr splits open allowing the chestnuts to fall free, onto the ground.

Uses: Production of nuts, hardwood timber and in overseas countries, hardwood timber and ground durable posts from the naturally rot resistant heartwood.

Latin Name: Castanea

Botanical Family: Fagaceae - this is also the beech and oak tree family. All chestnut species are native to northern hemisphere countries.

Species: Worldwide there are four main species along with several minor species. The four main species that have been utilised by mankind for their various produce are:

1) Japanese chestnut - Castanea crenata - a small to medium sized tree (~10 m), which is typically multi leadered and wide spreading. Some varieties have very large nuts (~40 g), which are nearly the size of small potatoes. Nuts of this species typically have difficult to remove inner skins (pellicles). This species is well adapted to wet and humid weather conditions and hot summers (~30oC). These trees have been present in New Zealand since the early 1900's, particularly in the upper North Island region.

2) Chinese chestnut - Castanea mollissima - a medium sized tree (~15 m), often multi branched and wide spreading. Nuts usually have easy to remove inner skins and come in a wide range of sizes, although typically smaller than the Japanese chestnut. At present the Chinese chestnut is a rare tree in New Zealand, but recent imports may change this.

3) American chestnut - Castanea dentata - the largest growing (~30 m) and straightest trunked of all the chestnut species, was once a prized timber tree in the USA before its demise due to the devastating fungus disease called chestnut blight. Nuts are typically very small (~5 g), but quite sweet tasting with easy to remove inner skins. This is a rare tree in New Zealand but recently has been imported through quarantine.

4) European chestnut - Castanea sativa - a large growing (~20 m) and wide spreading tree which originated from around Turkey and the Black Sea region of southern Russia. During Roman times this very versatile and adaptable species was introduced to most present day European countries where it has become naturalised, and today is a common part of the landscape in many regions. The nuts are quite variable but superior fruiting varieties possess good size, sweet taste and have easy to remove inner skins. This tree is the most commonly seen chestnut species in New Zealand where it was introduced by the early settlers. This species is also known as the sweet chestnut or the Spanish chestnut in English speaking countries.

Hybrids: Where the different species have been planted in close proximity to each other by man natural hybrids between the species occur readily. This has occurred in several countries around the world including New Zealand, where today large hybrid chestnut trees are common. Chestnut breeding programmes around the world have deliberately hybridised the various species to create superior varieties for fruit and/or timber production. European/Japanese hybrids are now the common commercial fruiting varieties in France, Australia, New Zealand and the western USA. Japanese/Chinese hybrid varieties are now found in South Korea and Japan. American/Chinese hybrid varieties are now found in the eastern USA along with even more complex hybrids.

Food Value: Chestnuts have a quite remarkable nutritional composition that sets them apart from all other nuts and makes them an outstanding food source which can be a dietary staple. The nuts are ~50% water when fresh, which makes them highly perishable. Chestnuts are made up of primarily complex carbohydrate, are low in protein (~5%) and are very low in fat (~1%), have reasonable quantities of vitamin C and potassium, are very low in sodium and are free of gluten, oil and cholesterol. The protein is of very high quality, comparable with eggs and is easily assimilated by the human body.

The flavour, texture and sweetness of the nuts from different chestnut species and varieties varies widely, from tasteless and bland to very sweet and flavoursome.

To Eat: One must first remove the outer shell and inner bitter tasting skin to obtain the edible kernel and although chestnuts can be eaten raw after peeling they are usually cooked in some way. Cooking methods vary widely but simply can be done by boiling the in-shell nuts whole for half an hour and then cutting them in half and scooping out the soft kernel flesh inside using a teaspoon. Another common way is to roast in-shell chestnuts in the oven, over hot embers or in the microwave, but you MUST pierce the shell with a small cut or cut them in half beforehand with a knife to prevent them from exploding when they cook! Specialised hand held chestnut peelers that remove the shell and inner skin together before cooking make the tiresome task of peeling chestnuts quite easy and quick. (These are available in New Zealand). Once you have peeled your chestnuts they may be cooked in a wide variety of ways - boiled, roasted, steamed, microwaved, pureed, soups, stuffings, sweet desserts and so on. The nuts can also be dried and ground into an excellent quality flour for bread, biscuits, gravies etc. Chestnuts are very diverse in their culinary uses and many classic recipes are popular worldwide.

Worldwide Production and Consumption: Huge tonnages (currently estimated in excess of 470,000 t) are produced and traded annually worldwide, mainly among northern hemisphere countries. For much of this century however, worldwide production has steadily declined, due mainly to disease, alternative land use and population pressure.

At the beginning of this century France, for example, grew nearly 400,000 t of chestnuts, alone. By the 1960s this had dropped to only ~45,000 t, dropping further to ~25,000 t by the 1980s, and to only ~11,000 t by 1995. Italy, Europe's biggest chestnut producer and exporter has likewise dropped from over 300,000 t in the 1950s to only ~65,000 t by 1995.

Today, the world's top ten leading chestnut producers are, firstly, China, then Turkey, Korea, Italy, Japan, Spain, Portugal, France, Greece and Albania, in descending order. Demand, even in most of these countries, however, continues to outstrip supply. Despite being the fifth largest producer in the world, Japan imports more than 33,000 t of chestnuts annually (more than 3 times its own production). In Europe, France imports more than two-thirds of the total chestnuts consumed there. Significant tonnages are also traded throughout the rest of Europe, the Americas (both North and South), Africa, Asia and the Middle East. The top ten chestnut importing countries, worldwide, are currently Japan, then France, Hong Kong, Switzerland, Brazil, USA, Germany, Austria, and UK and Italy (~70,999 t in total).

International chestnut prices have increased consistently over the last 20 years, fuelling the current renewed interest in chestnuts. "New" chestnut producing countries are now starting to appear on the world stage. The USA and some South American countries produce small quantities of chestnuts. Australia produces ~700 t (mostly for local consumption). Current New Zealand production is estimated at over 200 t. In both New Zealand and Australia production is rising.

In New Zealand Today

Based on research and trials conducted largely by the North Island Chestnut Action Group, the NZ Tree Crops Association, MAF and DSIR during the 1980's chestnut orchards today are being planted in New Zealand as an export orientated high value nut crop for sale as fresh produce and/or for processing. The chestnuts are produced from planned orchards of known performance based on grafted superior varieties. The industry is barely 15 years old but experience to date with chestnuts as a commercial orchard crop in New Zealand tells us the following:

Regions: Most producing orchards today have been established in the Waikato, Bay of Plenty and Auckland areas. However, chestnut trees will grow successfully across most of New Zealand and there are many new plantings established in Northland, Wairarapa, Levin and Canterbury.

Soil Type: Preferably free draining year round with an acid pH of around 5.5 to 6.5. Heavier, poorly-drained soils increase the likelihood of root rot problems (Phytophthora spp).

Topography: Flat to gently sloping land is preferred for ease of operation, (especially mowing and harvest).

Climate: A hot summer with maximum temperatures of at least 25-30oC to ripen the nuts. Regular rainfall over the summer and autumn months to ensure that the nuts reach their optimum size, otherwise irrigation may be required. Late spring frosts can be a problem in some regions by burning the new season foliage.

Altitude: Chestnut trees will grow well vegetatively at high altitudes in New Zealand but may not fruit at all or otherwise sporadically. These altitude limits for successful fruiting are still to be defined but could be as low as 500 m above sea level.

Shelter: Although chestnut trees are reasonably wind hardy and demand a high light intensity to promote female flower production, they grow and produce much better with effective shelter from the strong prevailing winds that are common across much of New Zealand, especially over late spring and early summer when new foliage is at its softest and prone to wind burn. Effective shelter is most needed when the trees are first planted and over their next few years when vegetative growth is at its maximum. Ideally, shelter lines should be planted 1-2 years before the orchard trees.

Orchard spacings: The most common spacing pattern is to initially plant the orchard at 6 x 6 m (256 trees/ha) and when the trees begin to intergrow to thin out the temporary trees to a final spacing of 12 x 12 m (64 trees/ha). Alternatively some growers plant at 12 x 12 m (64 trees/ha) particularly where the land between the trees can be intercropped.

Varieties (or cultivars): The most commonly planted varieties are the Euro/Japanese hybrids which are known by the following numbers - 1002, 1005 and 1015. All are characterised by rapid vegetative growth when young and are early bearing. Nut production will commence in the second or third season after planting if desired. To a much lesser degree there are plantings of the Japanese chestnut varieties Mayrick King, Mayrick Queen and 902, which appear to crop more heavily in the warmer regions such as the coastal Bay of Plenty and northern regions. The Japanese chestnut varieties often produce the largest nuts but the trees are not always as hardy as the Euro/Japanese varieties.

All these varieties produce chestnuts that possess difficult to remove inner skins that are easiest to prepare for cooking by peeling with the specialised chestnut peelers as described earlier.

Pollination: Chestnut trees require cross pollination from a different compatible variety to ensure good nut production. This means that an orchard planting must contain at least two different pollen producing varieties in a low ratio mix, such as 1:1 or 2:1. Pollination is carried out by wind and insects. Well pollinated chestnut trees will produce 2 or 3 plump nuts per burr. Chestnut trees that are not cross pollinated at all will still produce burrs every year but these will only contain 3 flattened empty shells lacking kernels, or on occasion poorly formed nuts.

Fertiliser: Chestnut trees respond well to a balanced fertiliser programme, whether it be organic or artificial. They need good supplies of nitrogen, potassium and magnesium in particular. Apply in the early spring and again mid summer, but remember the maxim 'a little and often' rather than one heavy application which can cause root burn and much of which is usually wasted.

Harvest: Chestnuts fall in the autumn and ideally should be gathered every day over peak nutfall because of their highly perishable nature and their susceptibility to predation by possums and rats which relish the nuts. Harvesting is usually done by hand, although there are now various mechanical or vacuum machines of various sizes (some are tractor powered, others are smaller and backpack style).

Storage: Because of their highly perishable nature freshly harvested chestnuts must be cool stored immediately at 0-2oC. To prevent dehydration under cool storage the chestnuts should also be placed into ventilated plastic bags (containing small holes). For small quantities in the household this can be done by keeping fresh chestnuts in the fridge, packed into ventilated plastic bags or the vegetable drawer. Once coolstored fresh chestnuts may keep in good condition for up to six months or even longer dependant on the level of fungal rot infection and the variety.

Packhouses: For orchards with chestnuts to sell there are industry registered packhouses that will store, grade and pack the chestnuts for export to industry standards.

Marketing: For the New Zealand industry to continue competing successfully long term into world markets focus must be on producing only top quality products, whether it be in processed or fresh nut sales. Our strengths from a marketing perspective are: we have a clean green and uncrowded environment (where high quality produce from organic production is easily achievable); New Zealand growers enjoy freedom from the world's major chestnut pests and diseases; and being southern hemisphere producers are able to provide a fresh product into the northern hemisphere in their off season.

Chestnuts are regarded as a very high health food product that few other foods can match, but few consumers realise this. Marketing efforts should always capitalise and promote this highly desirable attribute.

In the past, all growers belonging to the New Zealand Chestnut Council marketed their crop through Chestnut Exports NZ Ltd (CENZ): a growers' owned and operated company formed especially to market chestnuts for the New Zealand Chestnut Council. Today, a range of private companies process chestnuts. Chestnuts are also marketed domestically.

Industry Organisation: There is a national growers association called the NZ Chestnut Council which co-ordinates all aspects of the industry. Bimonthly newsletters are produced and there are numerous field days for growers. Comprehensive information on growing chestnuts in New Zealand is available from the Executive Director, Dr David Klinac, HortResearch Ruakura, Private Bag 3123, Hamilton. Phone [07] 858 4668, fax [07] 858 4700, or email info@nzcc.org.nz. Prospective growers, growers and anyone with an interest in chestnuts are encouraged to become members of NZCC.

Yields and Returns: NZ Chestnuts are exported around the world and also sold in New Zealand. Estimating grower returns and production levels per hectare is easier said than done, given the vagaries of the market place from year to year and the wide variation in tree performance from one site to another. However, growers gross returns (at gate) can range from $1.50-$3.00/kg depending on size or grade of the nuts, with the larger or earlier-season nuts usually fetching a premium. Small nuts are difficult to sell at a profit on the fresh fruit market and are utilised for processing into value added products. Harvesting costs range from 50c to $1.00/kg depending on tree age. Given reasonable conditions most orchards are capable of achieving around 4 tonnes/ha once the trees reach maturity by year 10. Average gross returns (calculated at $2.50/kg average) at maturity would then be in the vicinity of $7,500/hectare.

Compared to many horticultural crops a chestnut orchard is cheap to establish and maintain, and has a low time input requirement (except at harvest). This allows most orchard owners to follow additional vocations as well.

Processing: Overseas chestnuts are readily processed into a wide range of user friendly long life products that are designed for everyday consumption, and are available from the supermarket shelves. Continued emphasis on processing (versus export of fresh nuts) is expected to continue. Overseas processed products include peeled frozen free flow, canned whole peeled chestnuts, vacuum packed whole peeled chestnuts, sugared confectionery, purees, ice-cream, baby foods, chips, yoghurts, dried whole chestnuts, flour for bread and biscuits etc. Many products are sold on the health market for premium prices. By developing a range of processed products the New Zealand Chestnut industry avoids the pitfall of over reliance on a single market type (for example fresh nut) which could become over supplied at some stage thus crashing grower's returns.

Diseases & Pests: Overseas there are many serious and crippling pests and diseases that often make chestnut production uneconomic. New Zealand is indeed fortunate to be mainly free of most of these serious problems and this is the reason for the strict border controls and lengthy quarantine periods placed on the introduction of overseas chestnut plant material including seeds. If you travel overseas please do NOT bring back any fresh chestnuts in your pocket as many of these pathogens are spread by contaminated chestnuts that appear quite healthy. In New Zealand the main problems are:

Root rot caused by the soil-based fungal disease Phytophthora cinnamomi which usually kills the tree, (at any age), and is more prevalent on heavier soil types. Trees can be infected at the nursery stage so ensure your nursery supplier is certified as meeting the nursery standards as specified by the NZ Chestnut Council. Control with fungicides is difficult, however the use of trunk injections or foliar sprays with phosphorous acid as a preventative for healthy trees is currently under trial evaluation and showing promising results. To reduce exposure to root rot diseases it is not recommended that orchards are established on poor draining soils, prone to waterlogging.

Infection of the nuts while on the tree with the fungal diseases Phomopsis and Botrytis (and other fungi) can lead to rotten nuts at harvest and can cause serious losses even under cool storage.

A native insect - the grass grub beetle, will eat the soft new season foliage of chestnut trees in the late spring when they fly at dusk, often in quite staggering numbers. Young trees may be completely stripped.

Possums are especially damaging, eating the bark, leaves and breaking branches and relish eating the nuts when they fall to the ground at harvest.

Rabbits and hares will eat the bark of young trees.

Propagation: Chestnut varieties are propagated by grafting or budding onto a seedling rootstock. To help minimise graft incompatibility problems (where the upper part of the tree dies or becomes unthrifty after rejecting the lower rootstock which remains alive) it is recommended that trees are grafted or budded onto seedling rootstocks that have been grown from chestnut seed of the variety being propagated, and which come from known problem-free seedlines, or from NZCC certified seed orchards. For example, to propagate the variety '1005' are collected from 1005 trees as seed to be grown as seeding rootstocks and then grafted or budded 1005 scions.

Organic Production: Is easily achievable with chestnut orcharding especially in the drier regions where fungal problems are minimised. Alternative organically acceptable sources of fertiliser must be used. Weed control must not include the use of chemical herbicides. To become a bona fide organic chestnut grower strict guidelines as specified by the BIO-GRO NZ (P O Box 9693, Wellington) and DEMETER (P O Box 306, Napier) programmes must be followed. Contact The Soil & Health Association, P O Box 36 170, Northcote, Auckland, or phone [09] 443 8435 for details.

Timber & Posts: Although regarded overseas as a valuable and versatile hardwood, very little work has been done to ascertain the potential, quality and durability of New Zealand grown chestnut timber and posts. Chestnut trees have the ability to coppice readily, which means they will regrow from the stump when cut down.

False Chestnuts: Do not confuse true edible chestnuts with the semi-poisonous nuts of the commonly seen ornamental flowering Horse Chestnut tree which fall at the same time in autumn and are of a similar size, shape and colour. True edible chestnuts are readily recognisable from conkers (the nut of the common name for Horse Chestnut) by the point at the top of the nut. Conkers have no point on their flattened smooth tops.

Chinese water chestnuts, which are a common ingredient of Asian cooking, are grown beneath a swamp loving sedge. This plant is not related at all to true chestnuts.

Good luck: If you would like more information about New Zealand chestnuts then you should subscribe to the "Chestnutz News" newsletter, available to all members of the New Zealand Chestnut Council.

CONTACT THE NZCC

For further information about the New Zealand Chestnut Council, contact:

David Klinac (Executive Director)
Ruakura Research Centre,
Private Bag 3123,
Hamilton
Ph 07-858 4668
e-mail:info@nzcc.org.nz