Truffles are the underground fruiting bodies of some fungal species. They require particular climate conditions and soil types as well as suitable hosts in order to thrive. Truffles establish a symbiotic relationship with the roots of host trees, with each party receiving nutrients or minerals more efficiently through the relationship.
Truffles are found wild throughout the world and are highly prized by chefs. Due to their high value they are now extensively cultivated throughout much of the world, including Australia, New Zealand, the United Kingdom, the United States and Europe. Truffles prefer growing in areas with cool winters, damply warm springs and hot summers with intermittent annual rainfall around 28 inches. Cultivated truffle crops require a good water supply during their early stages to establish the host trees. Irrigation may be required in periods of drought, otherwise small and distorted fruits may result.
Ideal soils are well-drained and porous. Those over a chalk or limestone bedrock provide the correct pH of around 7.5 to 8.3 as well as minerals, but this does not exclude other shallow, gravelly soil types from use. Iron-rich red limestone with incorporated organic matter is considered best for black truffles, while Burgundy and white truffles are often seen on sandy soils in the wild.
Establishing a plantation requires shallow plowing of the soil and planting inoculated tree saplings impregnated with mycorrhiza fungi. After planting, weed suppression is necessary to ensure establishment of the trees without competition.
The black and Burgundy truffles grow successfully on host roots of English oak, which can take six to eight years to produce good commercial quantities of truffles. Mediterranean oak, also known as holly oak or holm oak, is faster growing than English oak and host to several truffle species. Downy or pubescence oak is native to southern Europe and southwest Asia and is often found as a host tree in the wild. European hazel is a fast-growing large shrub commonly used in truffle plantations due to the advantage of its nuts being a secondary crop. Douglas fir, found in Oregon and Washington, has been successfully inoculated with Oregon white truffle fungi.