Pines and pine nuts

When most people think of pine nuts, they would associate them with Pinus pinea, the Italian stone pine, which is the species most commonly grown commercially in Europe. However there are in fact twenty or more species of pine which produce edible “nuts” inside the cones (though more technically these are seeds rather than true nuts). Around half a dozen of these are important commercially, with the Korean pine Pinus koraiensis being popular in China, and its pine nuts are actually traded internationally in larger volumes than Pinus pinea pine nuts. Several species are also important in the Americas such as Pinus edulis from Colorado and Pinus cembroides from Mexico, which are both commercially harvested from the remaining native pine forests as well as being cultivated. The pine cones need to stay on the tree to ripen for up to several years depending on species, and generally require fairly stable temperature and humidity during spring and summer to produce high quality pine nuts.

We already had Pinus pinea growing, but these are fairly readily available so for something more exotic we have started with two other species, one larger and one smaller than the traditional Italian stone pine.

Coulter pines (Pinus coulteri), originally from California, are about the same size trees as Pinus pinea, typically attaining a height of around 20 meters, but the cones they produce can be more than twice as large, sometimes reaching as much as 40cm long and weighing up to 5kg! Intact cones can thus be quite impressive and a source of great fascination for children, but can present a fall hazard from mature trees. With other treefruit crops such as Jakfruit where the large fruit can present a fall hazard, it is common to prune the central growth tip of the tree once it reaches a certain height so that the eventual maximum height of the tree is reduced, reducing the hazard from falling fruit. This should also work for Coulter pines, though many people who grow them will prefer to allow them to reach their full natural size as they are attractive specimen trees so long as there is sufficient space to leave around them.

For something more suited to the typical suburban garden, another option is the Dwarf Mexican Pinyon pine (Pinus cembroides var bicolor). These are a dwarf varient of the commercially important Mexican pine nut which are much smaller growing with a maximum height of only 4-5 meters, though older trees can adopt a spreading habit and be wider than they are tall. Despite the smaller size of the trees, the cones and pine nuts produced are of equivalent quality to commercially grown varieties, and these represent a much more compact option than relatively large trees such as the traditional Pinus pinea.

Araucaria

Another major source of what are commonly referred to as “pine nuts” are the Araucaria trees, though in fact these are only distantly related to true pines and their fruit is a seed rather than a nut. These are part of an ancient lineage, the Araucariaceae, which also includes other well known trees such as the various species of Kauri and Australia’s rare Wollemi pine, which were common worldwide at the time of the dinosaurs but have since been outcompeted by more recently evolved trees in much of the world, especially the Northern hemisphere. All of these Araucariaceae are interesting and beautiful trees to grow, but only the araucaria species produce edible nuts.

There are 19 species of araucaria found in various parts of the Southern hemisphere, with two species in each of South America, Australia and Papua New Guinea, one on Norfolk Island (the well known Norfolk Island Pine, which is by far the most widely cultivated), and 13 species in New Caledonia where they have survived due to the island’s relative isolation, though many of these are now considered endangered. Aside from the ubiquitous Norfolk Island pine, the species most commonly encountered in New Zealand are probably the Monkeypuzzle and Bunya pine.

All araucariua species produce edible nuts, though only three of these are commonly harvested, these being Australia’s Bunya pine, the Monkeypuzzle from Chile, and the Paraná pine from Brazil and Argentina. Even Norfolk Island pines which are commonly grown as an ornamental tree, do produce edible nuts inside the cones, but these are rarely eaten as unlike most araucaria species where the ripe cones fall to the ground, with Norfolk Island pines the cones tend to stay attached to the high branches until they disintegrate. Araucaria trees tend to be fairly large and long lived species, and almost all nuts are harvested from remaining wild stands of mature trees, as they are generally considered too slow to bear fruit for viable commercial plantations, even though the yields from mature trees can be considerable.

The main exception is the Bunya pine, which has been cultivated commercially to a limited extent. The Bunya pine is both relatively fast to bear fruit, taking about 15 years to start fruiting (compared to Monkeypuzzle for example which can take 40 years), and also unusually for an araucaria can sometimes produce both male and female flowers on the same plant and be self-fertile, though in practice trees start off either male or female but they can start producing both types of flower if they are grown in isolation and can’t sense any other Bunya pines close by. Yields will be much higher from a larger group of mixed sex individuals than a single hermaphrodite specimen however.

Bunya pine cones are one of the largest of tree bourne fruit, weighing up to 10kg and measuring 35cm or more in length. The nuts inside are around 3-4cm long and can be eaten raw or cooked in various ways. Particularly heavy yields tend to happen at intervals of 2-7 years when conditions are favourable, and such “festival harvests” were important cultural events for indigenous people in pre-European times when thousands of people would gather at the Bunya forests in south-east Queensland. Due to the large size of the fruit there is a fall hazard underneath mature trees, especially during December-March when the cones mainly fall, and when the trees are grown as ornamentals people will often get an arborist in to trim off the unripe cones before they get too big. When the cones are desired for harvesting appropriate precautions should be taken around large trees, generally just a fence around the base and a warning sign seems to be the common approach, as the heavy weight of the cones tends to mean they only fall within the drip line of the tree. Another option might be to prune and shape the tree as it is growing to encourage a more spreading growth habit and reduce the maximum height.