In my personal experience (though many will disagree) there is no plant on earth that routinely works well with introduced mychorrizae.

I have used T22, stuff from fungiperfecti and others and none of it ever produced viable mychorrizae in containers or in the ground.

Conversely I had mychorrizae form naturally in one bed in the shade that I never introduced any innoculant to.

It formed on the roots of an evergreen shrub and ignored the annuals around it.

In my view this is a build it and it will come thing. If conditions are right then symbiotic fungi will grow and if conditions are not right you can spend lots of money on spores and innoculants and none of it will take. Being organic isn't enough. Most of these fungi live and thrive in very narrow environmental conditions.

2. I have read where tomatoes don't have the mycorrhizal association,

Sir Albert Howard suggested that the Mycorrhizal Fungi and its association with plants be studied back in the 1890'a but no one really did until just a short time ago and as a result we still do not know all we should about the relationship these fungi have with the plants. Some plants do have a symbiotic relationship while others do not appear to, such as the mustard family. Some lists of plants that do use these fungi list tomatoes while other lists do not have tomatoes on them.
What we do know, and have known since Sir Albert Howards days, is that many plants to form a symbiotic relationship with Mycorrhizal Fungi and both benefit from that relationship. We also know that tilling soil disturbs that relationship for a long time. What we do not know is whether innoculating soil with spores really is all that beneficial, because each plant species has specific Mycorrhizal Fungi that work with them and the fungi that works with plant species A may not do the same with plant species B.

I do think the entire mustard family does not use mycorhizzae. I am sure there are others, bit I do not know which ones they are.

Some mustards, such as garlic mustard, have escaped into the wild, where they disrupt mycorhizzal relationships of native wildflowers. It has become all too common to see woodlands that were once carpeted with trillium, dutchman's briches, bloodroot, asters, anenomes, leeks, and dozens of other species that are now monocultures of garlic mustard.

Thank you all for your input. I was reading -- possibly in Acres USA -- that mychorrizae have a value beyond increasing the water and nutrient intake of the plant they infect. Apparently they are a powerful source of added soil carbon, either by sloughing off pieces or by exudates, I'm not sure. This interests me because my pet theory is that loss of soil carbon has been the root cause of loss of natural fertility and, consequently, the reason for the popuarity of NPK fertility, pesticdes, and hebicides. Comments? Regards, Peter,

Your theory is correct, except it was the use of the synthetic fertilizers that caused the loss of soil organic matter as well as people not replenishing that organic matter. Liebig postulated that plants only need the NPK, theorizing that the rest would come from the soil and that was true as long as sufficient OM remained in the soil. Howard postualted that Liebig was wrong and all that was needed was organic matter including compost. Many of us, following the teachings of Sir Albert Howard have seen that this is true, compost and organic matter is all that is needed to maintain soil fertility.

Where can I pick this up?

Since mycorrhiza refers to a symbitoic relationship that certain fungi have with plants, and not to any specific fungi, those that sell "Mycorrhizal Fungi" are really seling you a magic elixar and you would be much better off and further ahead making your soil into that good, healthy soil where the fungi that will be naturally present will develop that symbiotic relationship without your spending your money on something that will not do much.

Mycorrhizal fungus develops naturally on the soil surface by the process of COLD composting. You can 'grow' your own by...
1. Using the Ruth Stout method of mulching with hay or straw. Never disturbing the soil, just keep mulching on the surface over the years, moving the mulch aside to plant. Toss veggie parts such as carrot tops, on top of the mulch to decompose.

2. Shredding leaves, branches, fall garden trimmings and returning them as a mulch under shrubs and trees.

3. Using bark mulches which are never disturbed except to plant.

4. Setting aside a dedicated, out-of-the-way spot under a shrub where you create a flat pile (never over 8" high) of clippings, grass cuttings that slowly cold compost. When planting you can reach under this pile gently and extract a bit of this rich soil to add to your new planting. MF develops on soil surface, so gently add it to the top of a new planting before mulching. Water well.

As Kimm says above, healthy soil/compost is good stuff. But, the trick to encouraging MF is to mulch and not disturb the soil any more than necessary. Not all plants utilize MF, but the various types will develop through cold composting for those that do.

At end of season, cut off all plants in garden that will not overwinter. Leave the roots in the garden to break down naturally. Do not till garden, but follow the above advice. Leaving the roots to decompose opens channels throughout your garden filled with rich OM that will attract and help reproduce beneficial fungal hyphae (sp?). This in turn will help nuture along mychorrizae's advance through the garden where it co exists with live plant roots. Only took me a few years to learn the hazards of tilling.