Certified quality plants cannot solely guaranty truffle cultivation success. In order to develop properly, truffles need a specific type of environment. Luckily, truffle cultivation conditions are now well documented. With lots of technique and a little bit of instinct, the harvest will be excellent and plentiful.
Geographic Location
Truffles like well-defined seasons. Optimal growth is achieved when the summer is hot and punctuated by abundant rainfalls. Fructification is triggered by temperatures below the freezing point during wintertime.
Weather Conditions for Truffle Cultivation
| Burgundy Truffle | Appalachian Truffle | |
|---|---|---|
| Annual rainfall (mm) | 400-1500 | 600-1500 |
| Days with rain | 40 to >80 | 50 to >80 |
| Maximum daily rainfall (mm) | 100 to >300 | 100 to 250 |
| Sunshine (hours) | 1500 to >3000 | 1700 to 3000 |
| Mean temperature, January (°C) | <-20 to 10 | <-20 to 0 |
| Mean temperature, July (°C) | <20 to 26 | <20 to 30 |
| Growth degree days | 1700 to >2500 | 1500 to >2500 |
Optimal Truffle Cultivation Zone on the East Coast of North America
SoIl
Truffles grow in well-drained limy soils. A south-facing slope with light alkaline soil meets the perfect conditions for truffle development. It is most important to test the soil texture of the site before implanting the truffière, since this parameter is difficult to modify. Even though sandy soils are usually recommended for truffle cultivation, both the Burgundy and the Appalachian truffles tolerate high percentages of clay, as shown in the soil texture triangles. However, clayey soils need more intensive loosening due to their compact nature.
Soil Texture Suitable for Burgundy Truffle Culture
Soil Texture Suitable for Appalachian Truffle Culture
In addition to soil texture, a few other parameters are essential to truffière productivity. The core ones are listed in the table below, and pH and carbon/nitrogen ratio are the most important among them.
Target Soil Parameters Values for Truffle Cultivation
| pH* | % Org. Matter | C/N Ratio | Ppm Phosphorus | Ppm Potassium | % Clay | |
|---|---|---|---|---|---|---|
| Burgundy Truffle | 7,0 – 8,0 | 3 – 20 | 5 – 20 | 5 – 75 | 145 – 1200 | < 60 |
| Appalachian Truffle | 7,5 – 8,5 | 1 – 10 | 6 – 15 | 3 – 20 | 120 – 250 | < 60 |
*Carbonate ions essential to truffle cultivation are added while liming to adjust pH.
Soil chemistry and biology are complex sciences. Thus, although the values in the table are useful references, they don’t assure truffle harvest. Contrariwise, even if the above-mentioned conditions are not strictly met, other parameter interactions could make truffière implantation possible on the chosen site. A future truffle producer would benefit from consulting with a specialist to evaluate the site and interpret the soil analysis results.
Vegetation Antecedents
Soil is a battlefield where microorganisms fight for nutrients and symbiosis plant partners. If truffle plants were planted on a site with too many ectomycorrhizal competitors, the truffle could be overthrown. The vegetation antecedents of the chosen land thus have to be taken into account.
Plants in association with endomycorrhizae are the best antecedents for truffle production. The soil on these sites is colonized by mushrooms which cannot compete with truffles.
- Agriculture
- Prairie
- Vine
- Orchard
Woodlands usually are unfavorable antecedents for truffle cultivation. Most woodland trees are associated with ectomycorrhizal mushrooms which can outcompete the truffle mycelium. Moreover, since spores survive in soil for more than a decade, great care should be taken with woodlandsrecently cut down.
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Growth of most ectomycorrhizal mushrooms is inhibited at high pH. It is thus possible to implant truffières on woodland sites if the pH has to be adjusted to meet truffles needs. Moreover, the Appalachian truffle is a very aggressive competitor which secures its symbiosis partnership. A combination of the Appalachian truffle with soil pH modification could be a suitable solution for sites with unfavorable antecedents.
Planting Truffle Trees
Soil Preparation
Soil preparation procedures depend on the soil type of the future truffière location. A tilling depth of 30 cm is sufficient for loose soil. This will avoid mixing rocks and sterile material with the nutrient-rich topsoil. On the other hand, the first 50 cm of soil that has not been worked for a long time will probably need to be decompacted with a subsoiler.
The nature of the selected site will dictate if the soil will be worked on its whole surface, or only on plantation rows. If the whole land surface needs to be perturbated, it is advised to plant a cover crop to avoid settlement of tall weeds which would interfere with tree growth.
More often than not, soils are acid, and soil preparation processes are not complete without lime application. Nutrient deficiencies and poor C/N ratios are usually adjusted concomitantly.
Planting Density
Planting density has to be planned carefully so the soil of the mature truffière receives just enough sunlight to warm the earth and ensure truffle development. In general, the deeper, richer, better irrigated soils call for dispersed planting, since such soil conditions promote tree growth. Higher density planting would yield early truffle production, but would in turn reduce the lifespan of the truffière by canopy closure.
To couple early productivity and longevity, it is possible to start with a dense plantation, and then thin out as the canopy is closing. Another interesting strategy to delay canopy closure would be to alternate tall wide trees, such as oak, with stockier trees, such as hazelnut.
Planting density also has to be adjusted according to truffle species. Indeed, the Burgundy truffle prefers cool and shaded environments; hence the recommended planting density of 600 to 1000 plants per hectare. On the other hand, the Appalachian truffle prefers warm bright areas, and the suggested planting density is 300 to 700 plants per hectare, accordingly.
Planting Technique
Truffle plants can be planted before the growth season in spring or before dormancy in fall. The technique requires a bit more caution than regular tree planting to avoid damaging the truffle mushroom.
- Dampen the clod and roots of the truffle plant.
- Dig a hole with a depth and diameter of 20 to 30 cm.
- Place the tree in the hole, keeping the clod intact.
- Make sure the collar is just under soil level.
- Fill the hole with fine dirt complying with truffle cultivation parameters.
- Compress the dirt by hand, making sure the dirt level near the trunk is slightly higher than the rim of the hole, to avoid water accumulation leading to root rot.
- Water the tree with 2 to 3 liters of water.
- Make sure the collar lies about 2 cm below the surface of the added dirt.
Adding a stake is highly recommended. To stimulate plant growth and ensure protection from animals, a mini Tubex greenhouse can be added to each tree.
Irrigation
A big fraction of truffle cultivation success is determined by proper water supplying. A truffière setup in drought-prone areas should include an irrigation system. Depending on the size of the truffière, a tank, a well, or a small artificial lake are suitable water reservoir options. Water should be dispensed through sprinklers to avoid damaging the mycorrhizae.
Truffière Maintenance
The life of a truffière is composed of three different stages. Each stage needs specific maintenance to promote root growth and preservation, which in turn will result in a generous truffle harvest.
Truffle Plant Settling
(1 to 3 years)
During the plant settling stage, the tree produces many fine roots on which mycorrhizae develop. Mycorrhizae development, to which truffle maturation is directly related, is highly dependent on water supply. Thus, during rainless periods, depending on soil type, each tree should receive between 5 to 10 liters of water every 8 to 12 days.
Weeding should also be performed in order to minimize competition for water, nutrients, and space. During springtime, mechanical weeding helps aerate the soil and promotes root growth. From the second year on, low branches should be pruned to avoid double trunks and to prevent disease spreading. A little fertilizer should also be laid around the tree in nutrient-poor areas.
Truffle Mycelium Expansion
(3 to 10 years)
It is once the tree properly settled that the truffle mycelium extends its symbiosis and colonizes extensively the surrounding soil. A zone of yellow withered vegetation, the brulé, will slowly appear around the tree trunk as the mycelium expands. From this stage on, soil aeration will become critical: truffles need space to develop.
The soil should be worked on a depth of around 20 cm to maximize aeration and to prune the roots. Root pruning is especially important for the Appalachian truffle, as it stimulates mycorrhizae development. Heavy machinery circulation in the truffière should be subsequently avoided, as it would compact the soil. Since water in excess could cause mycelium asphyxiation, soil moisture should be checked at a depth of 20 cm before watering, especially in clayey areas.
Proper pruning of trees in symbiosis with the Appalachian truffle is essential for truffière sustainability. This truffle needs an open canopy, so pruning efforts should be oriented towards obtaining tall thin trees. Since the Burgundy truffle prefers cool, shady environments, pruning of its symbiosis partner should be mostly aesthetic. At this stage, weeding is not necessary, and mowing should be preferred; the mycelium will benefit from the nutrients transferred by the decomposing grass. Once every 3 years, a soil analysis should nevertheless be performed to avoid any nutrient deficiency or pH fluctuation.
Fructification
(7 to 35 years)
At that stage, the objective is to preserve the work already completed! Water is critical for good truffle development, so natural water deprivation has to be counterbalanced by watering during dry periods.
Harvest
Truffle harvest generally occurs between 2 to 3 years after the first brulé display, which takes place 4 to 7 years after truffière planting. Man cannot detect the distinct scent of mature truffles beneath 40 cm of soil. The truffle cultivator thus has to team up with a truffle dog, which will scratch the soil upon finding the precious mushroom. The truffle cultivator can then excavate the fruit of his labor.
To promote harvest at optimal maturity, the truffière is visited at least once a week during peak season. Immature truffles are left to ripen, and will be harvested later on: from September to December for the Burgundy Truffle, and from August to December for the Appalachian truffle.
