With the arrival of autumn and basil plants stretching skyward and flowering, processing copious amounts of home-made pesto came to mind. Pine nuts being the other main requirement, imagine my surprise at walking out of the supermarket with a meagre bulk-bin plastic bag, and being charged $59.90 per kilo. So what's the story?
Remains of pine nuts and accompanying recipes have been found in the ruins of Pompeii. Roman and Greek poets bestowed aphrodisiac powers to the nut that has been supplying sustenance to man for thousands of years.
There are at least 18 species of the Pinaceae family that produce edible nuts but only four species have been cultivated for their seed crops, two in Europe and two in Mexico. The Korean pine (Pinus koraiensis) from China, and the Stone pine (Pinus pinea) from Europe are by far the main varieties found on New Zealand supermarket shelves.
Pinus pinea is a tree of the northern coastline of the Mediterranean, growing from Portugal and Spain in the west, to Lebanon in the east. Because cones open on the tree releasing the seeds, often in Europe trees are climbed and unopened cones removed and dried in the hot sun to open and release the seeds. The nuts are then cracked by rollers and very lightly roasted to remove a slight but natural turpentine like taste.
Large forests of Pinus koraiensis grow in a broad band across the top of Europe from Russia into Manchuria, China, and Korea. The Chinese fell huge numbers of these trees for timber and the pine nuts retrieved are a by product of forest clearance. It's a once only, extractive industry.
Most of the world's pine nut producing species can be grown in New Zealand, and there is evidence that good nut production can be obtained from some species. P.pinea is the most common species here and is a possible commercial species, but informed predictions will require more research according to the New Zealand Tree Crops Association.
Also known as Edible pinenut and Umbrella pine, the Stone pine is a large to medium evergreen tree that reaches 15-25m high with a broadly arched, umbrella shaped crown and horizontal branches. The straight but often leaning trunk has a furrowed, reddish grey bark. The rigid and paired needles are 10-20cm long and are bright to light green. These needles on the lower branches apparently deter rabbits and hares as they get a poke in the eye.
The trees can withstand strong winds and salt sea air, will grow in both sand and clays, and once established will tolerate very hot summers and cold conditions down to 23C below freezing. They can be used as a multipurpose crop in a shelter belt as the strong tap root is able to penetrate hard soils which helps when competing for water. The species will grow in 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.
Trees are best planted at a spacing of 10m for nut production or 5m as a shelter belt.
It's a slow growing tree that starts producing the globe shaped, shiny and brown cones in 6 to 8 years or 10 to 12 years on poor soils, taking 40 years to reach full production.
New Zealand harvesting is generally done with 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 then 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 the cones are left on concrete where the sun heats them. The cones will then open and you can retrieve the pinenuts.
The 20mm x 10mm nuts can range from 13-31% protein, are rich in oil with a soft texture and are a good source of vitamin B1 (thiamine).
Every 3 or 4 years a heavy crop is produced. Each cone holds about 50-100 nuts and 100 kg of cones holds about 20kg of nuts. Annual nut yields are about 5 kg per tree, but 15kg in a good year, so 100 trees per hectare can give yields of 500-1500kg of nuts per hectare. Not bad, currently retailing at $59.90 a kilo.
Thanks to Judy Bool, Publications Officer, New Zealand Tree Crop Association Inc. for the supply of reference material for this article.
