I am currently reading an excellent book on the subject of mycorrhizal fungi. There is a lot of talk on line about the relationship between these helpful fungi and our trees, some of the talk appears to be accurate but a lot is unhelpful and inaccurate. I will draw out a few of the more interesting relevant points for you all.

  1. The first fact is the amazing one: the length of mycorrhirae can be 10,000 times longer than the roots of the tree!!!!
  2. The roots seem to ‘call out’ to the spores of the fungi by using chemical signatures given off by the roots in the soil – these can reach at most to about 15mm. The spores then grow towards the roots and prepare for their arrival by communicating back with other chemicals.
  3. If the roots have sufficient nutrients they emit less of these chemicals as they seem to have less need of the beneficial fungi. In this way the plant controls the relationship
  4. There are thousands of different species of fungi that can form these symbiotic (mutually beneficial) relationships, most are capable of making contact with a range of host plants, but sometimes only a single species.
  5. However the benefit of a certain species of fungi attaching to a certain species of tree will depend entirely on the external factors of the soil (water, nutrient, temperature, etc). There is not a single ‘best’ combination!
  6.  It would seem that for a company to market a packet of spores without stating which species of tree they will work for is either showing a lack of understanding or, at worse, willfully misleading!
  7. Some fungi grow on young roots and then as the soil ‘matures’ other older growth fungi species out-compete and the soil flora changes naturally over a decade or more.
  8. Mycorrhizae are like the leaves on the trees, they flourish in the warm summer months and can die back almost entirely in the winter (when the tree has dropped its leaves and is not producing energy) only to regrow the next year
  9. More to come when I have read the next chapter…

The book is Mycorrhizal Functioning, edited by M. Allen (’93), 534 pages of hardcore science…