Everyone has heard stories of people going into the woods to gather truffles and most of us have probably wondered why such a highly prized food item would grow in the forest. In fact, truffles are a very special type of fungus (like mushrooms) that can only grow in a symbiotic relationship with roots of certain trees. They cannot grow alone. To grow your own truffles, and especially if you're growing in a greenhouse, make sure you have adequate space and time for a "truffle orchard."
Choose your site. Truffles and their trees--truffle orchards--can be grown inside a very large greenhouse but need plenty of sunlight and southern exposure. A greenhouse will provide the necessary warmth and protection but try to use a greenhouse that has clear glass to allow full sun, with windows that open to the south. Choose a greenhouse that is large enough to house many trees.
Prepare the soil in your greenhouse. Clear it of any branches, rocks or weeds to give the truffle orchard a clean growing experience. Oak trees are very hardy and do not require any special amendments in their soil. Truffles, on the other hand, require lime to grow. Turn over the top 12 inches of your soil and mix in a compost foundation and lime supplement. End with a mix of approximately 50 per cent garden soil, 40 per cent compost and 10 per cent lime.
Purchase oak trees injected with truffle fungus from an approved truffle grower. Since truffles are not native to the United States, this is the only way to obtain a truffle growing foundation.
Plant your oak trees to grow your truffle orchard. Dig holes that are twice as wide as the trees' roots and at least 2 feet deep. Place the trees in their holes, spread the roots, fill the holes with soil and pack it down, using your hands. While planting, manage only one tree at a time; take it through the entire planting process before you begin with the next tree, to make sure the roots don't dry out and kill both the tree and the truffle fungus. Oak trees can handle some crowding, so use a measure of 500 trees per acre. Downsize the number to fit your greenhouse.
Water your orchard well and maintain the moisture throughout the year. Oak trees do well with lots of water and the moisture is vital for the formation of truffles. Build an irrigation system in your greenhouse or utilise an overhead misting system to maintain the moisture in the soil.
Keep the oak trees mulched to protect the trees and truffles from cold temperatures and to further maintain the moisture. Use organic mulches like wood chips, grass clippings and leaves for the ideal truffle-growing situation.
Truffles can take up to five years from planting to harvest. Truffles grow best in mid-Atlantic states like North Carolina.
Small plantings (fewer than 500 trees) can result in a lack of colonisation for truffles.