I am considering growing some Porcini mushrooms (Boletus edulis) under a maple tree in my backyard. The tree is ~10 years old and is very lush; so I imagine that at its base there might be enough shade for the Porcini to grow. There is also a good layer of mulch at the base of the maple. Will the Porcini form a symbiotic relationship with the maple? What things can I do to enhance my chances of producing mushrooms and of helping out the maple?
No, maples do not grow symbiotically with Porcini or any ectomycorrhizal species. They only grow with vesicular-arbuscular (VA) mycorrhizal fungi, which do not fruit. While other trees have been innoculated with Porcini, there is little evidence that thees trees eventually produce mishrooms.
Boletus aedulis, ie Porcini, Best variety. It is mainly found in the woods of oak and chestnut of the plain, and beech and fir forests of the high mountains. It is symbiotic fungi, gregarious, which can develop in groups of many specimens.
EDIT - Second answer
Porcini mushrooms are protected across Europe. In Austria it is forbidden even to touch them.
In Italy the Forest Guard and some allowed growers sell fir trees (small and medium size), with roots already inoculated with hyphae of porcine. A cultivation for dissemination of spores is considered impossible, to no success.
They carry pieces of soil with some roots with hyphae and place them between the roots of small spruce trees, or on the base, in the ground, before a transplant. They are then allowed to grow (fir and mushroom) and create a full symbiosis. Then they sell the fir inoculated with his "bread" of soil without touching the roots.
The fir tree is then planted in the ground of the buyer, and monitored for several years.
I have absolutely no idea how to play the private cultivation in Canada.