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Snake Oil

Guest Article for the Tallahassee Democrat

January 10, 2014

By Stan Rosenthal

If you go to the internet and look up snake oil you will find the following definition from the source Wikipedia:

“Snake oil is an expression that originally referred to fraudulent health products or unproven medicine but has come to refer to any product with questionable or unverifiable quality or benefit. By extension, a snake oil salesman is someone who knowingly sells fraudulent goods or who is himself or herself a fraud, quack, charlatan, and the like.”

As an Extension Agent with the University of Florida my job is to promote research based information.  Thus “snake oil” when defined as “any product with questionable or unverifiable quality or benefit” is contrary to what we in Extension are trying to accomplish.  Now to make a point, just because a product is unverifiable doesn’t mean that it won’t work or will not be verifiable in the future.  The problem is that these products are often a waste of time and money and in some cases do harm.  Purchasing such products would be like buying a car from someone you didn’t know and you were not able to test drive the car until after you bought it.

An example of snake oil that I run across with trees is the use of mycorrhizae-forming fungi. Mycorrhiza is a symbiotic relationship (mutually beneficial) with plants and fungi that forms in the roots system of plants. Without going into a lot of detail, we know that plants are helped by this relationship as the fungus helps plants take up water and nutrients better.  Although we are far from knowing all the types of mycorrhizae-forming fungi, we know that there are thousands of types and that most plants (including trees) have this association.  We also know from fossil records that this fungi and plant relationship has been going on for hundreds of millions of years.

How many species of mycorrhizae-forming fungi are there?  We actually don’t know.  There are no doubt, many, many species that benefit our trees.  The problem is that many mycorrhizae-forming fungi species are unique to a particular tree species.  In some cases, specific species of mycorrhizae have been identified and added to soil that specific tree species can benefit from where it wasn’t already available in the soil.  This, at times, has shown great results in tree growth and health.  A quick search on the internet will show you that you can buy a bag of mycorrhizae-forming fungi for your trees.  A few are targeted for specific species but most are sold as a one-size-fits-all cocktail.  Of these two categories, the one to be most skeptical of is the one-size-fits-all cocktail because it con­tains a plethora of fungal species simply in the hopes that one will be the appropriate species to fit the tree.  It is very unlikely this will help your trees.  In fact, it is likely that you already have this fungus in your soil.  If not, it is doubtful that it is the specific fungi that you need.  This concern is backed up by research, such as a study published by the University of Florida’s Dr. Gilman in 2001.  This study found that adding spores of mycorrhizae-forming fungi to the backfill soil around recently transplanted trees, had no impact on tree survival or growth.

So how do you protect against being sold snake oil?  First, remember anyone can act as if they are an expert whether on the internet or in person.  Check your sources.  Second, just because someone used something and thinks it fixed their problem doesn’t mean it is true.  Often, when these situations are looked at objectively, they can be explained by another factor that occurred that the claimant was not aware of.  Finally, take care as to determine what the motivation of the seller is.  Is his/her main goal to sell you something to make money?   For example tree paint, packaged to heal pruning cuts on trees, was found to do nothing positive for the tree, although I am sure much of it was sold to homeowners’ trying to help their trees.

Stan Rosenthal is an Extension Agent with Leon County/University of Florida IFAS Extension.  For more information about gardening in our area, visit the UF/ IFAS Leon County Extension website at  For gardening questions, email us at


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