Mycorrhizal innoculants?

dwheeler at dwheeler at
Sat Nov 29 13:32:13 EST 1997

Mycorrhizae are fungi that associate with the feeder roots of plants,
assisting in water and nutrient absorption. Some have also been found to
associate with nitrogen-fixing bacteria, presumably increasing the growth
of trees without fertilization. Mycorrhizae can fruit as individual
spores in soil; as truffles; as mushrooms like King Bolete, matsutake,
chanterelles, or Amanita mushrooms. The interest to foresters is that
these fungi can probably also increase the growth of trees tremendously,
and may be more valuable than the trees themselves.

Thousands of citations for mycorrhizae can be found on the internet. So:
how many foresters a) know they exist, and b) use them?

Many mycorrhizae are species specific, that is to say, they associate
only with one species of plant. Other mycorrhizae are associated with
many hosts. For example, Pisolithus tinctorius has been found to
associate with a wide variety of plants in near wasteland environments.
Thus, it is a good fungi to inoculate with plants in areas where survival
rates are nearly non- existent and where normal soil mycorrhizae have
been decimated, as from construction or mining activities. However, P.t.
doesn't really encourage plants to grow rapidly. It merely sustains life.
P.t. is often replaced by other mycorrhizae when sufficient organic
matter is added to soil.

Several years ago, I started messing around with mycorrhizal fungi.
Douglas fir without mycorrhizal fungi don't live for long. Trees with
mycorrhizae tend to grow rapidly. Quercus palustra at least locally tends
to grow several feet a year, even with locally acidic rain, provided a
species of Scleroderma is present. Has anyone else worked with
mycorrhizal inoculation of seedlings or established trees?

With 10 years of research/observation from a local Christmas tree farm
near Oregon City, I can now say there appears to be a clear and profound
change of mycorrhizae as trees mature. Recent data suggests that a single
half- centimeter of root can be a host to 7 different species of
mycorrhizae. Many mycorrhizae are apparently more valuable for the
mushroom market the the host tree is worth on the timber market: truffles
come immediately to mind, which typically sell for several hundred
dollars per pound, and can produce several pounds per tree. I have
successfully produced several species of native truffle with Douglas fir.
This effectively increases the production and harvest schedule, all while
increasing growth rates. Certain trees can produce a variety of truffles
within the same year, usually 3-4 species of truffles. Last July a
mycologist with Oregon State University examined the closest rootlets we
could find near Tuber giganteum Gilkey. Oddly, nearly all of the roots
were inoculated not with Tuber, but with another fungus that had been
inoculated earlier. Yet nearly all the truffles found were Tubers, or
true truffles!

Has anyone examined their trees for truffle production? And if not, why?

Daniel B. Wheeler

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