Pine Nut

Classification: Pinaceae

Other names for Pinus pinea

Stone Pine, Edible Pinenut, Umbrella Pine

Introduction

Many species of pines bear edible pine nuts. These nuts are actually the kernels which are released when pine seeds are cracked open, and each cone usually has numerous seeds. Different pine species have different sized seeds, different ease of cracking and different flavours – the worst tasting strongly of turpentine. Pine nuts are very nutritious and have been an integral part of the native diet in many parts of the northern hemisphere for thousands of years.
There are at least 18 species that produce edible nuts. However, only four species have been cultivated for their seed crops – Pinus pinea and P. sibirica in Europe, and P. cembroides and P. maximartinezii in Mexico. Other species are regularly collected from native forests. Some of these sources, especially in China, are dwindling as the forests are felled for timber. The pine nuts you usually find in the shops are nearly always from the Stone pine (Pinus pinea) from Italy or the Korean Pine (Pinus koraiensis) from China.
A number of pine species producing edible nuts grow well in New Zealand, with the drier parts of the South Island recognised for good seed production. P. pinea is the most common species here and is occasionally described as a possible commercial species. However, considerably more research needs to be done before informed predictions can be made about a potential pine nut industry.

Description

The evergreen tree is medium or large, reaching 15—25m high, with a broadly-arched, umbrella-shaped crown and horizontal branches. The often leaning straight trunk has a furrowed, reddish grey bark.
Needles are in twos, persisting for 2 years, stiff and light green. Cones are usually borne singly (occasionally in twos and threes) inclined downwards at the end of branches on stalks; they are nearly round, 80—150mm long, and up to 100mm wide; they ripen in their third year. Seeds are thick-shelled and dull brown with variable-sized wings. The tree is hardy to minus 12°C.
This tree comes originally from the Mediterranean area where the nuts have been used for centuries — shells have even been found in Britain in the refuse pits of Roman encampments. Italy is the main grower of this species and produces the bulk of the world supply. The seeds are especially valuable in Spain, Portugal and Italy, and are called pignolias.

Climatic Requirements

Hardy Zones 8-10
The trees can stand strong winds and salt sea air, and once established will tolerate both wet and dry conditions.

Soils

The species will grow on almost any soil other than a highly alkaline lime soil. If grown on permanently wet soils, such as peat, the tap root will fail to develop and the trees will blow over because of heavy top growth.

Sites

These trees can be used as a multi-purpose crop in a shelter belt as the strong tap root on this species is able to penetrate hard soils, a feature which helps when competing for water. Low branches develop which remain green all their lives and lower branches tend to deter rabbits and hares while the tree is young: apparently they do not like pine needles in their eyes!
In coastal areas they are particularly useful for shelter belts and erosion control as they tolerate salt laden winds and will grow in both sands and clays. They also cope with very hot summers and cold conditions down to 23C below freezing.
It is now being recommended to plant pine nuts on sandy sites where the branching will be lighter and a good salt wind blowing through will help obtain good nut production. (This has been disputed by some growers in other areas.)

Spacing

Trees are best planted at a spacing of 10m for nut production or 5m if planted as a shelter belt.

Propagation

Pine seeds need varying amounts of cold treatment (stratification) before they will germinate. If sown directly into the field, rodents and birds may damage the seeds. Seeds should be sown in a well-drained potting mix, preferably in deep pots and covered with 10mm of mix and kept at about 19°C. Higher temperatures inhibit germination. When germination occurs a long taproot will grow before the shoot emerges. Take care not to damage this taproot.
A layer of pine needles or soil from beneath an established pine tree may be helpful in establishing mycorrhizal infection around the seedling roots. This soil will probably contain fungi which live in close physical association with the pine, to their mutual benefit. In fact, these symbiotic fungi are essential for the trees to grow and remain healthy. Without this mycorrhizal association seedlings may simply stop growing after a couple of years. Unfortunately, different pine species need different fungi. Young plants are susceptible to frost damage. Seedlings do not need shading except in very hot and sunny locations.

Transplanting

The trees transplant badly if they are left in one place for more than 2 years because of the long taproot and sparse root system.
Plant into permanent positions as soon as possible. Mulch will help suppress weeds.

Pruning

It is desirable to prune trees from year 3 to remove all the lower branches up to a height for access. Clearing of the lower branches facilitates the production and harvesting of the nuts and enables sheep to graze As the growth of branches begins close to the ground, the lower branches can become large if left unpruned. The extent of the growth lower branches is very much determined by the spacing between trees. Removal of the lower branches and removal of a second leader, if it develops, also improves the value of the tree for timber.
For nut production make sure that the tree has a single trunk and develops into an umbrella/parasol shape. This provides enough height to walk underneath when gathering the cones. If exuberant growth as on fertile soils, remove about every second branch so that the sap flow is not impeded – thus preventing the formation of nuts.

Pollination

Flowers are self fertile and pollinated by wind They form November to December and the seed ripens about April. This species does not hybridise with other members of this genus.

Production

These trees are slow growing. Seedling trees can start producing cones in 6 to 8 years, but may take as long as 10—12 years on poor soils, with full production by 40 years. This is obviously dependent on how the trees grow, so the better the treatment you give them the sooner they will produce nuts.
A heavy crop (mast) is produced every 3 or 4 years. Each cone holds about 50—100 nuts and 100kg of cones holds about 20kg of nuts. This means that annual yields of nuts are about 5kg per tree, but 15kg per tree in a mast year. With 100 trees per hectare this gives yields of 500-1500kg of nuts per hectare.

Harvesting

Harvesting is done by a long pole or hook which is used to pull the cones off the tree. Mechanical harvesting using tree shakers is being introduced. The nuts are crushed between cylinders to crack the shells which are separated off by sieving, then the kernels are sieved again to remove their brown skin Where no equipment is available leave the cones on concrete where the sun heats it. The cones will then open and you can retrieve the pinenuts.

Nuts

The seed 20mm x 10mm is rich in oil and has a soft texture. It is commonly used in snacks and Pesto sauce. Store in a dry place (not the refrigerator). Unshelled pinenuts stay fresh longer than shelled ones.

Pests & Diseases

An easy to grow tree with little in the way of pests and diseases in New Zealand, but not necessarily productive.

Cultivars

Thin-shelled varieties exist. The variety ‘Fragilis’ has a thin shell and is cultivated for this reason. Work is being done in Italy to select superior cropping plants. Rootstocks for these need to be 18 months old, and a cleft or veneer side graft is used.

Other Edible Species

Of the 18 species of pine which produce edible nuts the species of the most interest to us in New Zealand are: Pinus pinea, P. edulis, P. koraiensis, P. cembroides and P. coulteri. Other possibilities are: P. armandii, P. maximartinezii, P. caneriensis, P. monophylla, P. quadrifolia and P. sibirica.

P. koraiensis (Chinese nut pine, Korean pine)

A medium or large pyramidal tree of loose conical shape, this species grows to a height of 20—30m with a trunk up to 2·5m in diameter. Branches are strongly horizontal to erect. Needles are in fives, loosely arranged, stiff, green on one side and bluish-white on the other. Cones are borne at or near the end of branches in groups of 1—3, are cylindrical and erect, 90—140mm long by 50—60mm wide, bright yellowish-brown when ripe, with woody scales. In New Zealand cones ripen in their 2nd year in March and the seeds fall a month later. These seeds are greyish-brown and unwinged. In its native habitat of Manchuria, Korea and north Japan it grows on mountains, usually in well-drained sandy soils, in mixed forests of conifers and hardwoods. It is hardy to minus 35°C, but not good on wet sites.
Trees start to bear cones at 25—30 years of age, with heavy seed years occurring every 2—3 years. Cones contain, on average, about 160 seeds.
The nuts are highly valued in Asia, where numerous improved selections exist. In North America two improved selections, ‘Grimo’ and ‘Morgan’, are available.
At present cones are collected in conjunction with logging operations in north-eastern Chinese forests which are being over-cut. The cost of seed collection will increase enormously as trees become scarcer. In 1981 there were 390,000ha of this species, but by the year 2,000 it is anticipated that the accessible timber will have been logged.
When seed is collected in conjunction with logging operations it makes the seed collection cost extremely low — as workers have been receiving wages as low as $US1.00 per day. Thus, immediate market prospects for cultivated edible pine seeds from New Zealand are not bright.

P. edulis (syn. P. cembroides var. edulis) (Pinyon pine)

This medium-size tree (to 15m high) is usually multi-stemmed with irregular habit. It would need training with a single stem if cultivated. In New Zealand the cones usually open in March or April after a frost, the seeds falling out over the next 2 weeks.
Native to the high mountain slopes in south west USA and Mexico and hardy to minus 22°C, this slow-growing straggling tree has adapted to a dry climate. Trees under 250mm diameter appear to be dioecious, providing fewer cones but many seeds per cone, but larger trees seem to be monoecious and produce many cones, but with fewer seeds per cone.
Young trees start bearing at about 25 years old and when about 1·5—3m high. Heavy crops are not borne until trees are about 75 years old. Because of this time factor there are no cultivated orchards of pinyon pines.
Cones take 2—3 years to mature, and large crops are expected every 4 to 7 years. Trees can be shaken to get the seeds to fall on plastic sheets. (A traditional harvest method used by the Amerindians was to allow kangaroo rats to collect the nuts and store them in a tunnel a few inches under the ground, and then raid these stores.)
Unshelled nuts have excellent keeping qualities, and can be stored for 3 years. Shelled nuts must be used within 3 months. Pinyon nuts contain 20 essential amino-acids, and have been used in the USA for centuries, where demand always exceeds supply.

P. cembroides (Mexican pinyon, Mexican stone pine)

In commercial importance this nut is second only to P. edulis. It is slow-growing, tolerant of competition, and very long-lived, not reaching maturity until 250-350 years old.
It is a small tree, growing to 8m high, with a rounded crown and outspread branches. The cones are roundish, 30—50mm long by 30—40mm wide, with only a few scales which open widely when ripe. It is native to south-west USA and Mexico where it grows on hot arid mountain slopes, and is hardy to minus 15°C.

P. coulteri (Big cone pine)

This is a large, straight-stemmed tree, 25-30m high, with a loose, green, pyramidal crown and very stout wide-spreading branches. The bark is thick and very dark brown. Needles are in threes, persisting for 2—3 years, and are long, stiff and dark bluish-green. Cones are borne on short stalks and are very large and heavy (250—350mm long and up to 150mm wide), a shiny yellow-brown, and very persistent. Most cones open to release the seeds, which are black with a 25mm wing. This species is native to the coastal mountains of California and Mexico and is hardy to minus 15°C. Trees are quite fast-growing and drought-tolerant.

P. maximartinezii

This species is proving to be a very difficult species to establish with our present knowledge. The late Louis Trap reported that his were only 50cm tall after 4 years, with many deaths. It can withstand cold winters and is probably better suited to colder drier sites in the South Island. In its native habitat of Mexico this tree is not very big, 5—10m high, with a trunk 150—250mm in diameter. The branches are irregular and drooping. One of the largest trees Louis saw was 20m high and had a 600mm trunk diameter. Obviously if we can find the ideal conditions to suit this tree it will grow larger than in its natural habitat.
The cones are very large, 100—220mm long and 100—150mm wide, and can weigh up to 2 kg. They are borne singly and appear pendulous on slender branchlets. The seeds are wingless, oblong and a very light brown in colour, 10—12mm wide and 20—25mm long — reportedly the longest pine nut in the world. These nuts (800—900 to the kilo) are available on the local Mexican market. The seed coat is thick and very hard.

P. armandii (Chinese white pine)

One of the more easily-grown species, this pine begins flowering quite early, around 12 years of age. Native to the mountains of western and central China, it is hardy to minus 23°C. The seeds are regularly collected and sold in the markets there and regarded as a delicacy.

Other Species

Several other species produce edible nuts but are of much less significance. Of these P. monophylla and P. quadrifolia appear promising. Peter Leerschool mentions growing P. caneriensis in the Wairarapa. Nick Ledgard of NZ Forest Research Institute, Rangiora, obtained seed of 10 species in 1987, and no doubt different individuals have imported several more. How these are all doing and where they are is not clear.

Conclusion

Most of the world’s pinenut-producing species can be grown in New Zealand, and there is evidence that good nut production can be obtained from some species. P. pinea and P. koraiensis have already shown their ability to grow and produce good nuts. P. pinea appears suited to dry areas and P. koraiensis to the moister, more humid sites.(Especially around Lake Coleridge). They are the most encouraging species so far.
The Korean pine is interesting because its cones fall intact, making it less costly to harvest than the other pines. P. maximartinezii, because of its large seeds, should be tried also.

Commercially, the cost of production, length of time to cropping and the prices received are at present hardly enough to make a viable industry, and immediate market prospects for cultivated edible pine nuts from New Zealand are not bright.

Nevertheless, the total market size has increased significantly over the past decade with the advent of health food consciousness. So we should be looking ahead and trying out different species and management, so that we are then in a position to exploit any future market opportunities. In the longer term there may be room for optimism, and ongoing research should not be neglected. It would certainly be beneficial to select precocious early and heavy cropping trees. The length of time to maturity for some species seems daunting. If high-producing seed lines can be found and better orchard management techniques developed to maximise seed production, future prospects could be improved. Until this is done, pine nuts are likely to remain a cottage industry for lifestyle enterprises or a small adjunct to another major business.

References

L. Trap: Pinus Pinea. Growing Today 4(3)13.
L. Trap: Update on Pinus Pinea. The Tree Cropper, Issue l, Sept 1994.
P. Leerschool: Pine nuts in the Wairarapa. The Tree Cropper, Issue 2, Dec 1994.
L. Trap: Pinus maximartenesii. The Tree Cropper, Issue 9, Sept 1996.
D. Richardson: Report – Production & Marketing of Edible Pine Nuts.
M. Crawford: Pine Nuts. (Northern Hemisphere Revue.)
M. Ledgard: Pine Nuts in New Zealand. The Tree Cropper, Issue 3, Mar 1995.
L. Trap: Pinus Pinea: An edible nut pine of many uses, Australian New Crops Newsletter, Issue 6, 1996
Plants for a Future, The Field, Cornwall England – Internet Site

Compiled by: Roy Hart – May 1997

Updated by: G Newcomb – November 1998
Privacy removals and proprietory format conversion – December 2007

This fact sheet has been produced with the latest information available at the time of publication. In no way, however, can this sheet 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, then we ask you to write to the contact below.