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Plant Focus

First described by the Japanese botanist Bunzō Hayata in 1913, Quercus hypophaea is a medium to large evergreen oak restricted to the...

Truffle-oaks in Argentina

Where were most oaks planted in Argentina during the last three years? One might guess that it would be in one of the collections of the few quixotic quercophiles in that country, or perhaps a landscape designer with a preference for Quercus was responsible, or a particularly zealous specialist nursery. But the answer lies in the activities of Trufas del Nuevo Mundo (Truffles of the New World), a new truffle-oak cultivation enterprise that recently completed planting a sizeable 50-hectare trufera (truffle orchard) with Holm oak (Quercus ilex) and English oak (Quercus robur), for a total of 20,249 trees.

Truffle-oaks at Trufas del Nuevo Mundo's plantation in Espartillar, Argentina.

Members who attended the 7th IOS Conference in Bordeaux may recall Pierre Sourzat’s presentation on “Black Truffles and Oak Trees in France and in Europe,” where he explained the important role played by oaks in the production of Périgord black truffle (Tuber melanosporum). Truffles, a highly-prized culinary delicacy, are the fruiting bodies of a fungus that flourishes as a mycorrhizal association with the roots of trees, especially oaks.

A row of Quercus ilex

The fungus is better than root hairs at absorbing minerals and water from the soil and provides these nutrients to the roots of the tree in exchange for carbohydrates. The mycelium of the fungus in effect extends the trees’ roots and makes them more efficient. The fungus that develops as mycorrhizae then produces underground fruit, which contain spores and pheromones that match the sex pheromone found in boar’s saliva. Pigs will sniff the truffle, dig it up and eat it, in the process spreading the spores. The scent that makes truffles irresistible to pigs has a similar effect on humans and makes them highly sought-after by discerning palates, and therefore highly valued too, fetching around €1,000 for 1 kg. Truffles were first harvested in European forests using domesticated pigs (you had to be quick to make sure you got the truffle before the pig gobbled it, and that you did not lose a finger in the process), and about 200 years ago it was accidentally discovered that you could plant trees in fields in truffle country and later harvest truffles in these “artificial” truffle orchards. Coppicing or pruning the trees was later found to increase production. In the 1970s, seedlings were deliberately inoculated with truffle fungi and cultivation began in earnest. Dogs are now used to harvest truffles: they are just as efficient at smelling the underground treasure (once they have been trained) and have the advantage that they do not wolf them down!

The principal truffle-producing countries are France, Italy and Spain, but cultivation has taken off in the Southern Hemisphere in areas with appropriate climatic conditions. Truffles require calcareous soils and a Mediterranean climate, without summer droughts or excessive winter cold that can freeze the truffle in the soil. Propitious conditions can be found in Australia and New Zealand, currently the largest producers in the

Don Cecilio Segovia, caretaker of a truffle orchard in Lobería, Argentina, is more accustomed to rounding up herds of cattle on horseback. Now he hunts for truffles with the dog he has been training for the last two years.

Southern Hemisphere (in fact, Australia aims to overtake its European competitors and become the largest producer of black truffles within the next decade), and also in South Africa and South America. Cultivation began in South Africa and Chile about ten years ago and in Argentina in 2010. Southern Hemisphere producers enjoy a specific advantage: truffles are best fresh and are harvested only in winter months, so producers below the Equator can offer their wares to Northern Hemisphere consumers when they are out of season.

The people behind Trufas del Nuevo Mundo first researched the project and joined forces with experts from Spain and Chile to obtain the necessary know-how. They next examined the soil and climate conditions of several areas in Argentina before deciding where to buy land to set up their trufera. The site chosen lies about 500 km south-west of Buenos Aires and has ideal climate. The soil is not calcareous, but that can be corrected: the first step was to add lime to the land in order to bring the pH close to 8. Inoculated seedlings were produced in their own specialized nursery nearby, and in 2012 the first plantations

Oak trees planted at a density of 400 trees per hectare (165 per acre)

began. The species chosen were Quercus ilex and Q. robur, as seed is easily obtained in Argentina from mature trees. In Europe, Q. pubescens and Q. cerris are also used extensively.

Another preliminary step involved scarification of the soil, which at this site is shallow and rests on a layer of calcrete, a calcareous sedimentary rock. As the rock is impervious to water, it creates poor drainage conditions inimical to truffles and would also mean trees would grow with a shallow root system and be vulnerable to strong winds. A massive mechanical hoe was used to dig furrows that broke through the underlying rock (see a video here). Trees were then planted in a pattern that favors efficiency but is far from picturesque: straight rows 8 meters apart, with trees planted every 3 meters. The rows run north-south, in order to maximize the amount of sunlight reaching the soil, a necessary condition for truffle fruiting. With 12.5 rows every 100 meters, and 33.3 trees in a 100 meters 100 meters of row, they pack in over 400 trees per hectare (about 165 per acre), thus obtaining a total in excess of 20,000 trees in the 50-hectare plantation.

Young trees need protection against rodents (hares particularly can wreak havoc), so plastic tree tubes were installed.  The strong winds meant a solution had to be found to provide support, as the stake holding up the

A taut wire running along the entire row helps support the seedlings against strong winds

tree shelter was not enough. It was decided to use an adapted espalier system, similar to what is used a vineyards: a wire is stretched along the row, at a height of about 50 cm, and the tree tubes are fastened to it, thus providing the necessary support.

Irrigation is required to help the trees become established and subsequently to provide humidity necessary for truffles during summer. A sprinkler is placed at each tree, ensuring water is spread around the tree, thus encouraging root growth and extending the area where truffles might grow.

The project has been financed by means of an investment trust, with shares available to outside investors, a structure that has been used for similar enterprises in other countries. It is a long term investment, as the first truffles are not expected to be harvested until the fifth season at the earliest and peak production is only reached after 10 years. However, if current prices are maintained — the combination of limited production

Viewing a section of root under a microscope to determine the presence of mycorrhizae (the small nodules visible bottom right)

and increasing demand suggest that might be the case — the potential returns are attractive. The first black truffles have already been harvested in Argentina. In 2014, a truffle was found in a private small-scale truffle orchard planted in 2010 in the district of Lobería, closer to the Atlantic coast. This year (2015) truffles weighing over 270 g were found in another private orchard, close to Trufas del Nuevo Mundo’s plantation.  In the large plantation, there is evidence of truffle potential: “scorched zones” around the trees, known as brûlé, marked by an absence of grass due to competition from the fungus, and mycorrhiza on the roots which can be observed in samples under a microscope. With these encouraging results, it looks like many more oaks will be planted in Argentina in coming years.

Young oaks in the first plantation at Trufas del Nuevo Mundo (2012) - note the sprinkler in the foreground.  Pedro Bercetche, owner of the truffle orchard in Lobería, where the first black truffle was harvested in Argentina. The trees were planted in 2010.

Further reading:

Trufas del Nuevo Mundo website (in Spanish): www.trufasdelnuevomundo.com
Australian Truffle Growers Association: www.trufflegrowers.com.au
New Zealand Truffle Association: www.nztruffles.org.nz 
In Search of the Best American Truffles" (Article in The Wall Street Journal)