Tuber aestivum (summer truffle) or Tuber uncinatum (Burgundy truffle) is a hypogeous (growing and its living below the surface of the ground), ectomycorrhizal ascomycetes in the genus Tuber. These specie is valued for its gastronomic significance and is found across a wide range of temperate European regions. Morphologically, it is characterized by spherical to irregular fruiting bodies (2 to 7 cm in diameter), dark brown to black peridia (outer skin) covered with prominent polygonal warts and light-colored gleba (inner flesh) with intricate white marbling, T. uncinatum often displays a darker gleba and a more intense aroma than T. aestivum (Paolocci et al. 2004).

For a long time these two species have been considered as separate species because they looked different. However, modern DNA analysis has revealed that they are actually just two different physical forms of the very same species (Wedén et al. 2005; Molinier et al. 2013). According to scientific naming rules, the oldest name has priority, so T. aestivum is now the correct official name, and T. uncinatum is just synonym word for it (Wedén et al. 2005).

Ecologically, this species forms ectomycorrhizae with a broad suite of deciduous hosts—most commonly oak (Quercus spp.), hazel (Corylus avellana), beech (Fagus sylvatica), and hornbeam (Carpinus betulus)—and occasionally with conifers in mixed stands. It thrives in well-drained, calcareous soils, often overlying sedimentary bedrock, where pH generally ranges from neutral to slightly alkaline (Iotti et al. 2016).

Fruiting phenology differs between morphotypes:

• Summer truffle ecotype (T. aestivum): May–September

• Burgundy ecotype (T. uncinatum): September–January (autumn-winter)

The autumn–winter ecotype typically develops a richer volatile profile and slightly darker gleba than the summer form (Paolocci et al. 2004; Molinier et al. 2013).

Due to its adaptability and culinary appeal, Tuber aestivum is widely cultivated and harvested in Europe and has become a cornerstone of truffle agroforestry.

In its native range, Tuber aestivum is often found in the same areas as Tuber melanosporum but can tolerate a wider range of climates and soils. It is found in the wild throughout Europe as far north as southern Sweden and the UK, and it is successfully farmed both in the Northern and Southern Hemisphere.

Host trees are typically broad leaved trees (e.g. hazel, linden) and these truffles fruit more readily under a more dense tree canopy than Tuber melanosporum.

 

Tuber aestivum tolerates a wider range of soil types than Tuber melanosporum. This species can can be a good option in areas with poorly draining soils such as silty clay and silty clay loam soils.

Tuber aestivum occupies a wide ecological range in Europe and parts of North Africa. Its distribution is shaped by specific climatic conditions, soil types, and symbiotic associations with host trees. They are natively most successful in temperate climates with calcareous, well-drained soils and form crucial symbioses with deciduous trees. Understanding their ecological preferences is essential for effective conservation and cultivation strategies.

Geographical Distribution

T. aestivum and T. uncinatum are broadly distributed across Europe, from Mediterranean regions to more temperate and even continental zones in the north and east. Key regions include France, Italy, Spain, Germany, Switzerland, Hungary, Romania, Bulgaria, and Sweden (Weden et al., 2004; Büntgen et al., 2017). In North Africa, T. aestivum has been found in suitable ecological pockets in Morocco and Algeria (Mouhaddab et al., 2023).

In France, T. uncinatum dominates in eastern regions such as Burgundy, Champagne, Lorraine, and Alsace (Robin Pépinières, n.d.). In Hungary, natural habitats are found in the Jászság region under deciduous forest stands (Oláh et al., 2019). Isolated populations in Gotland, Sweden, demonstrate the species’ ability to adapt to colder, less typical climates (Weden et al., 2004).

Climate Preferences

T. aestivum thrives in temperate climates. Optimal mean annual temperatures range between 7°C and 12°C (45°F and 54°F), with winter lows near 1°C  (34°F) (Papp et al., 2020; Tănase et al., 2020). Precipitation ranges between 400 mm and 1500 mm (16 in and 59 in) annually, with well-distributed rainfall preferred over strong seasonal variation (Mouhaddab et al., 2023).

T. uncinatum is considered better adapted to cooler, more humid environments, typically found at higher altitudes or latitudes compared to T. aestivum (Robin Pépinières, n.d.).

Soil Characteristics

Tuber eastivum prefers calcareous soils with the following characteristics (Oláh et al., 2019; Tănase et al., 2020):

• pH: Slightly basic, optimum at 7.5 accommodating a range between 6.5 and 8.5

• Texture: Well-drained with moderate clay content (up to 40%)

• Organic matter: High (up to 20%), with a carbon:nitrogen ratio close to 20:1

In Hungarian truffle-producing areas, chernozems (soils characterized by high organic matter) and gleysols (soils characterized as being waterlogged) dominate, while in Transylvania, pH values from 5.9 to 9.4 have been recorded in productive soils (Tănase et al., 2020).

Ecological Niche and Symbiosis

T. aestivum forms obligate ectomycorrhizal relationships with deciduous trees such as:

• Corylus avellana (hazel)

• Quercus robur (English oak)

• Carpinus betulus (hornbeam)

Burgundy truffle is harvested in the Northern Hemisphere: August – December
Summer truffle is harvested in the Northern Hemisphere: June – August

The asci (sac-like structures containing a fungal spores) are typically somewhat spherical to broadly oval, measuring 90–120 × 70–100 µm, and generally contain 3-8 ascospores (a spore contained in an ascus) each. The ascospores themselves are roughly spherical, (25–)30–40 µm in diameter, with a finely reticulate ornamentation of ridges and spines 3–5 µm high. In maturing specimens, the spore surface ridges thicken and may fuse into a more alveolate (contains holes) pattern (Paolocci et al. 2004; Wedén et al. 2005).

 

 

Color: yellowish-brown to ochre when young, dark-brown when older

Surface: characteristically wooly surface, due to the presence of many curled, interwoven cystidia

Mantle: pseudoparenchymatous with angular cells in the outer and inner layers

Summer truffles have a strong, earthy, and musky aroma with nutty undertones. The fragrance is considered less intense than Tuber melanosporum but still quite distinctive. The flavor is delicate, with subtle notes of hazelnut and forest mushroom.
Burgundy truffle is more pungent than the Summer truffle. It resists heat better than other truffles and it can be used in cooked dishes like pate, sausages, sauces, soups, or omelets, but be mindful not to overcook as it can mute the delicate flavor.
Both are often thinly shaved raw over pasta, risotto, salads, carpaccio, or even toast with olive oil.,
Summer and Burgundy Truffle must be eaten within 2 weeks from time of harvest.