Tuber Melanosporum Truffle
Farming Guide

What are truffles and what varieties exist?

Truffles are the fruiting body of a mycorrhizal fungus, meaning they live in symbiosis with the roots of certain trees such as oaks, holm oaks, hazelnuts, some pines, and even shrubs like rockrose. Truffles grow underground, and some species produce an aroma to attract animals that dig them up and spread their spores by eating them. This aroma is also appreciated by humans and recognized by trained dogs used to harvest them.

Truffles belong to the genus Tuber. There are around 40 species, but only a few have real market value, such as the black truffle or Périgord truffle (Tuber melanosporum), the winter truffle (Tuber brumale), the summer truffle (Tuber aestivum) and its autumn cousin, the Burgundy truffle (Tuber aestivum var. uncinatum); the highly valued white truffle (Tuber magnatum), and the less expensive bianchetto (Tuber borchii).

Most of the information in this guide relates to melanosporum, but for more on other truffles, see:

  • Burgundy Truffle (Tuber uncinatum)

  • Bianchetto (Tuber borchii)

  • White Truffle (Tuber magnatum)

 

Geological Characteristics of Truffle Grounds

Black truffles naturally grow at altitudes between 100 and 1,500 meters above sea level. At higher altitudes, they prefer sunnier exposures. The same goes for latitude—moving north into colder climates, truffles need more direct light, such as south-facing slopes or less canopy cover.

Slightly sloped areas are recommended to avoid waterlogging in flat or valley bottom areas (unless the subsoil has good drainage), and very steep slopes should be avoided due to erosion and the complexity of mechanization.

Black truffles grow naturally in calcareous soils of the Mediterranean region. In Spain, they are mainly found in the eastern half of the country, over geological formations from the Primary, Secondary-Mesozoic (Triassic, Jurassic, Cretaceous), Tertiary, and Quaternary periods, mostly on hard limestones from the Upper Jurassic.

Characteristics of Truffle-Producing Soil

Although truffles grow in soils with varied textures and nutrients, it’s strongly recommended to perform a soil analysis before planting. Soil can be modified before planting, but some conditions should be avoided: clay content above 35% (to avoid compaction), and the following nutrient thresholds should not be exceeded:

  • Phosphorus < 40 ppm
  • Nitrogen < 0.5%
  • Potassium < 600 ppm

 

Truffles need active carbonate, with ideal calcium content around 10,000 ppm. Calcium ions are thought to be the “ammunition” used by truffle mycelium to stress the tree while demanding sugars.

Once the plantation matures, it’s better to perform foliar analysis to monitor nutrient concentrations for optimal tree health and photosynthesis, which supports greater truffle yields.

Soil horizons should be evaluated before preparing the land to confirm carbonate presence and analyze pH (should be between 7.5–8.5). To raise pH, a general rule is to add 2 tons of limestone per hectare for every 0.1 pH increase. For example, raising pH from 5.8 to 7.8 would require 40 tons/ha of crushed limestone, mixed into the top 20 cm of soil.

Excellent drainage is essential. To test for carbonates, drip diluted hydrochloric acid (muriatic acid) on the soil and observe if it fizzes.

The area marked in each triangle refers to the soil textures in which each truffle variety is found naturally. However, in truffle farms there should be no more than 30% clay for the black truffle and sandier textures must be found for the bianchetto truffle.

The ph ranges for fruiting of the three truffle varieties are relatively wide, but the optimum range for all of them is similar, i.e. between 7.5 and 8.

The three images correspond to profiles of soil found under natural truffères. The middle profile has a thin limestone crust. The one on the right is fissured bedrock but does not hinder the passage of roots or drainage necessary for good truffle production.

The tables compare the characteristics of soils that are favorable and unfavorable for truffle production. The favorable column lists some of the characteristics that indicate good drainage and aeration. This data provides very useful information for subsequent work on the plantation.

Soil Profile of a Truffle Plantation

There should be no clear layer breaks in the soil profile.

  • Soil should have a crumb structure with spherical particles.
  • Avoid prismatic structures, which signal leaching.
  • Laminar structures indicate compaction or flooding.
  • Poorly structured soil cracks and hardens in dry weather.

Climate for Black Truffles

Black truffles adapt well to dry, warm conditions—typical of a humid temperate Mediterranean or cool sub-humid climate. Ideal conditions include:

  • Warm, humid springs

  • Dry summers with occasional storms

  • Frost-free early autumns

  • Winters without extended freezing

Since truffle harvesting occurs in winter, regions with average winter temperatures below 0ºC or long snow periods pose challenges:

  1. Frost damage to shallow truffles

  2. Difficulty working with dogs to harvest

Temperature in °C

Anual Average

Average hottest month

Average coldest month

Absolute maximum

Absolute minimum

8.6 – 14.8

16.5 – 23.5

1 – 8.2

35 – 42

(-9) – (-25)

The optimal temperature ranges for the growth of black truffles vary once again. The temperatures in their geographic distribution area are depicted here.

Annual rainfall in Spain should be between 425–900 mm (600–1500 mm in Italy and France), with 48–64 mm monthly rainfall from June to August, typically from summer storms.

Tuber melanosporum begins forming in late May to early June and may produce multiple “flushes” through summer. Moist soil in summer and autumn is important for growth and weight gain.

Irrigation is critical, especially when using peat-based products to create truffle nests for adding complementary mating types. These materials increase water needs and irrigation frequency in summer.

Previous Crops and Contamination Risks

Previous crops affect organic matter, fertility, and potential fungal contamination.

Best previous crops include cereals, legumes, alfalfa, and most fruit trees (except hazelnuts, figs, pecans, and walnuts due to contamination risks).

It’s recommended to dig a trench to cut roots from nearby trees and prevent contamination in the new plantation. The trench can double as a drainage system. It can be left open (tractor hazard) or lined with geotextile and filled with stones.

Note: Wild tree roots can reach up to twice the tree’s height.

Host plant selection

Truffles grow in symbiosis with a wide variety of trees (see table below). However, only a few of them are used for cultivation. Currently, in Spain, around 90% of black truffle plantations use cold-resistant holm oak (Quercus ilex ssp. rotundifolia), followed by other oaks (Quercus pubescens, Quercus faginea). Hazelnut trees (Corylus avellana) have been mostly abandoned for black truffle cultivation due to their higher long-term contamination rates and the realization that co-cultivating hazelnuts and truffles is complicated (for example, hazelnuts must be harvested in the fall when the soil is moist, and heavy machinery is used, which compacts the soil and harms the truffles). In some countries, like the East Coast of the U.S., hazelnut trees are sensitive to filbert blight, which eventually kills them—although some resistant varieties are now being released. On the other hand, on the West Coast of the U.S., evergreen oaks can be more susceptible to sudden oak death, although the European strain of this disease has not affected well-managed and well-irrigated plantations (with no stress).

Tree Density and Planting Pattern for Truffle Orchards

Densities between 300–600 trees per hectare are recommended for black truffles. In the past, lower densities were chosen when soils were deeper and richer, and the trees grew faster. However, today there is a trend in agriculture toward medium-high tree densities in order to achieve higher yields and to balance management costs through the use of specialized machinery. The higher the density, the greater the initial yields, although it’s important to note that in the long term (plantations over 20 years), yields may end up being the same regardless of tree density, since yield is more related to the final tree canopy cover.

In warmer climates with high solar radiation, black truffles seek shade and closed canopies (80% canopy), whereas in colder climates with low radiation at higher latitudes, black truffles seek direct sunlight with canopies around 40%. As a general rule, when the average temperature in the hottest month exceeds 23°C or when solar radiation in that month exceeds 8kWh per square meter, the truffle starts to look for extra shade, and it must be provided in some way.

In the past, spacing was 6×6m or 7×7m, but today there is a trend toward 6×3m (550 trees/ha) or similar. In this case, it’s better to plant the rows from north to south, allowing the sun to illuminate the entire row evenly. Otherwise, if rows are planted from east to west, one side of the tree will receive more sunlight, leading to higher water loss and typically smaller truffles than those on the shaded north side of the tree.

Truffle cultivation involves avoiding soil compaction and not passing over the active truffle zone, which is achieved using offset implements. The increasing use of this type of machinery has made a minimum row width of 6 meters necessary to work comfortably.

How to Cultivate Black Truffles:
Soil Preparation and Planting of Truffle Oaks

In the images, you can see the most common tasks and machinery used to prepare the soil for truffle planting.

If liming is necessary—as is often done using heavy machinery—we recommend leaving subsoiling as the final step. It’s important to keep in mind that avoiding soil compaction is one of the main pillars of successful truffle cultivation.

Planting can be done manually, although for larger plantations, it is more cost-effective to use a GPS-guided tractor, as shown in the following video:

Immediately after planting, we sometimes use a geotextile—white on top, black underneath—to control weeds during the first 3 years:

However, the geotextile can be easily replaced by an in-row weeder during the first 3–4 years:

Subsoiler or ripper to break compacted layers. Apply 2–6 months before planting.

Moldboard plow to clean soil when previous crops left roots or stumps. Apply 2–6 months before planting.

Stone crusher to produce gravel for regular truffle shapes and protect dogs’ paws. Apply 2–6 months before planting.

Rotovator or tiller to loosen soil just before planting.

GPS-guided planter for fast, accurate mechanized planting.

Geotextile row cover for weed control and moisture balance; use double-layer (black/white) in warm zones.

How Black Truffles Reproduce and What It Means for Cultivation

Black truffles have two sexes—or mating types—that are necessary for sexual reproduction and fruiting body formation. When we study these mycelia with opposite mating types (commonly referred to as MAT), we see that they tend to avoid each other. As a result, by the time truffle orchards reach production age (6–8 years), several trees may lose one of the two MATs and will no longer produce truffles. Additionally, all the mycorrhizae in the soil act as females, while the males come from germinating spores that serve as the male factor to fertilize the female mycelium in the soil.

To produce a truffle, you need a “father” mycelium, which comes from a germinating spore, to fertilize a “mother” mycelium that comes from the roots and mycorrhizae. These two must be of opposite mating types. To compensate for the loss of MAT diversity, studies have shown that adding fresh truffle spores increases truffle production. Similarly, soil cultivation may help spread the MAT mycelia, potentially improving fertilization chances.

Economic Considerations

The cultivation areas for black truffles and summer truffles on calcareous soils are generally of low agronomic quality. These regions in the southern Mediterranean of Europe are often used for low-yield agricultural crops and tend to depend on government aid for survival. Truffle growers, however, no longer need to rely on subsidies, as they can earn up to three times more than with traditional crops in these areas. In fact, a surprising outcome has been the increase in agricultural land value in truffle-producing regions.

On the other hand, in other countries (such as Chile, Argentina, the U.S., and Australia), the land used for truffle cultivation is of higher quality—suitable for other profitable crops. In these cases, it’s not as clear that truffles are significantly more lucrative than other perennial crops like cherries, blueberries, or table grapes. For this reason, it’s essential to conduct a thorough, country-specific feasibility study before investing in truffle cultivation.

Spain, where it’s estimated that around 10,000 families are involved in the cultivation and harvesting of truffles, accounts for between 30% and 50% of the global black truffle production. However, very few people work exclusively as truffle hunters. Most combine truffle hunting with other jobs, do it on weekends, or align their vacations with the harvest season. A full-time truffle hunter today collects between 3 and 5 kg of wild black truffle per week—far from the 8–12 kg per day reported by veteran hunters in the 1940s–60s.

The price of black truffles in Spain varies significantly depending on the season’s yield. Prices follow a traditional supply-and-demand model, where higher yields result in lower prices. Truffle farmers are typically paid between €200 and €850 per kilogram for unwashed, ungraded black truffles, with an average of €400/kg. For summer truffles, collectors receive between €35 and €80 per kilogram.

The turnover volume of these truffles, between collectors and truffle growers, ranges from €600,000 to €15 million annually—figures that rise significantly after processing and packaging. In the European Union, average production in a good year reaches around 200 tons, but this can drop to a third in years with droughts and heatwaves. At the beginning of the 20th century, the 1,000 tons harvested at that time were easily absorbed by the market. In 1966, France alone was estimated to have a demand of 340 tons of truffles. Considering today’s higher standard of living and increased population, current demand is likely much greater. In other words, there is a growing demand for an insufficient supply of black truffles.

 

Profitability of Truffle Cultivation

How much can a truffle plantation produce? There are references of individual trees producing up to 10 kg of truffles, and some plantations of holm oaks inoculated with black truffle reaching yields of 200 kg/ha/year. However, some plantations never begin to produce due to various reasons, so truffle cultivation as a business is not without risks.

In modern truffle farming, once standards for tree certification were established and the quality of inoculated plants improved, technical plantations with irrigation, fertigation, and added truffle spores began fruiting earlier (with first truffles harvested around years 3–4). Most plantations produce 20–40 kg/ha/year until years 10–14, when they typically “take off” and reach commercial yields of 40–80–120 kg/ha/year or even higher in exceptional cases.

In Spain, a minimum production of 8–10 kg/ha/year is needed to recover the initial investment.

In other countries, where initial costs are higher (e.g., liming to raise soil pH or higher prices for truffle-inoculated plants), more truffles must be harvested before reaching profitability—or, put another way, the production cost per kilo of truffle is higher.

There are known wild truffle-producing trees over 100 years old with “burnt” zones over 12 meters in diameter that are still producing. However, the useful lifespan of a modern black truffle plantation is estimated at 30 years. Around year 25, yields typically begin to decline, and truffles become smaller. This is mostly due to increasing contamination of the host tree’s roots by other wild fungi year after year. Additionally, truffles seem to favor “fresh” soil, and once the area is fully colonized, something appears to be “missing” from the soil. For this reason, after 30 years, it is not feasible to cut down the trees and replant the same area with truffles—it’s better to switch to a different crop on the same plot.

Current net values for plantations in Spain, France, and Italy range between €19,424/ha and €66,972/ha. The average internal rate of return (IRR) is always above 9%, and the investment payback period is 10 years or more.

The sale price of truffles is estimated at €400/kg (unwashed truffles, mixed quality).

Extra costs not included here:

  • More advanced irrigation systems, with moisture and temperature sensors, online monitoring and control, and fertigation tanks: approx. €10,000/ha
  • Well drilling, construction of a water storage tank, pump house, and filtration system
  • Liming to raise soil pH to the optimal 7.8
  • Tractor and equipment: rotary harrow, vibrocultivators, branch shredder, auger or trencher for truffle nests