Last Saturday I went to hunt truffles to Tarragona, in an area rather peculiar. Peculiar because truffles (melanosporum and brumale) fruit naturally on licorella (a kind of slate rocks) acid soils with no carbonates and pH of 7 or below.
In the picture you can see the chestnut tree under which we gathered Tuber brumale. A few years ago, chesnuts were good truffle producers, but over 10 years ago Tuber melanosporum no longer fruits there. Chestnut trees have canker and have been dying and thus truffles underneath. The new shoots coming out, they die in a few years and there is not enough time to generate new truffieres.
Chestnut tree does not produce a burnt due to the amount of litter and debris that accumulates on the ground. In fact, truffles come under the leaves, as does Tuber uncinatum in beech forest. Black truffles, when used to fruit in those chestnut trees, were numerous but small in size (as a brumale). Tuber aestivum appears to be very rare in chestnut out in that area, although I remember the summer truffle had been described in northern Portugal under Castanea.
We finished the day hunting Tuber melanosporum under holm oaks in the same area were licorella has an acid reaction. Studies of these areas, which are already underway, can give valuable information, especially for growing truffles in the southern hemisphere, where the truffle is growing artificially in acid limed soils.
In another post I will explain the “trick” to make this happen and practical consequences for truffle growing on acid soils.
Marcos S. Morcillo