Purdue Extension Service

Vanderburgh County, Indiana

Additives Not Needed When Transplanting

By Larry Caplan, Extension Horticulture Educator, Vanderburgh County, IN

For the Evansville Courier and Press, March 21, 2008

There are many products on the market that claim they should be added to the soil when planting trees and shrubs to guarantee success. Seaweed extracts, formulations of amino acids, "magic microbes," and other products claim to reduce stress in plants. A popular additive is vitamin B1, also called thiamine, which supposedly protects plants from transplant shock.

I've seen advertisements and magazine articles that say there is research to endorse the use of these products, but is there any truth to these claims? Is there any credible unbiased University research to back up the marketing hype?

According to Dr. Mike Mickelbart of Purdue's Department of Horticulture, the original claim that vitamin B1 would aid in root development came 80 years ago when a scientific paper describing the "growth factor" effects of vitamin B1 was published. Based on that paper, chemical companies began to market vitamin B1 as an agrochemical, to be used when transplanting. The thought was that the vitamin would increase root growth in transplanted plants, and therefore aid in their establishment.

The problem is that the companies extrapolated the lab tests to the field without actually testing to see if it was true. The original research was to examine the effect of vitamin B1 on pieces of cut roots (no shoots present). We now know that vitamin B1 is produced in the leaves and transported down to the roots naturally, so that a transplanted shrub or tree is already producing the material, and does not need us to add more of it.

Also, further research showed that is wasn't vitamin B1 acting alone that enhanced root growth. Far more important is a growth regulator called "auxin." If you've ever used a "rooting hormone" when trying to grow cuttings, you are using an artificial form of auxin.

A third problem with adding vitamin B1, extracts, or any other carbon-based compounds to the soil is that they are often used as a food source by soil microbes. Most of the time, the compounds are broken down before the plant can take it up.

Some ads provide anecdotal evidence from unnamed gardeners who swear by the results of the product. However, these gardeners didn't perform a controlled study, comparing plants treated with the vitamin with those that were not treated. If the plants did well, was it because of the vitamin, or was it just a really good spring? (As a matter of fact, several universities HAVE tested vitamin B1, and have found no effects on plant growth or root development.)

Bottom line: don't fall for expensive or fancy-sounding short cuts. The best way to successfully transplant trees, shrubs, flowers and vegetables is to prepare the soil properly, plant properly, and water properly. Anything else is just untested voodoo.

For more information on proper planting, contact the Purdue Extension Service at (812) 435-5287.