Vitamin B-1: The Garden Myth That Won't Die

 Gardeners, their parents and their grandparents have heard this refrain at nurseries for decades: "Get a bottle of B-1, it will help reduce transplant shock for that new plant you are buying."

The truth, though, is the same as it has been for 70 years: it isn't the Vitamin B-1 (thiamine hydrochloride) in the bottle that reduces transplant shock.

First a definition of "transplant shock" from Purdue University: "Transplant shock is a term that refers to a number of stresses occurring in recently transplanted trees and shrubs. It involves failure of the plant to root well, consequently the plant becomes poorly established in the landscape. New transplants do not have extensive root systems, and they are frequently stressed by lack of sufficient water. Plants suffering from water stress may be more susceptible to injury from other causes such as the weather, insects, or disease. When several stresses are being experienced, the plant may no longer be able to function properly."

And right there you have the answer to effectively reduce transplant shock: water correctly.

Thiamine exists in nature, produced for plants via leaves and sunlight. Plants, as well as soil microbes, create their own Vitamin B1. Thiamine is a cofactor (molecule that binds to an enzyme to help/allow it to function) important in the construction and break down of carbohydrates for growth or energy storage/release.

In the 1930's, thiamine was shown to increase root development in plant tissue cultures - in the lab - especially in the dark. But those results couldn’t be replicated consistently in the field.


 Research at the University of California has shown that the addition of Vitamin B-1 to a plant doesn't make any difference at all.

Tests done at Sunset Magazine showed similar results: it's not the Vitamin B-1, it's the other ingredients in the bottle that might make a difference in roots and growth of new plants.


Back in the 1940's, naturally occurring plant growth regulators, known as auxins, were isolated and tested. Auxins were found to stimulate cell elongation in roots and stem tissue. Bingo!

Around that time, a commercial product, Transplantone, was developed that contained auxins and thiamine. Later research showed that it was the auxins, not the thiamine, that encouraged roots. 

But the die was cast: gardeners got into the habit of getting vitamins for their plants.

What does stimulate root growth? A rooting hormone containing auxins such as Indole Butyric Acid, Naphthylacetic acid or Paclobutryzol. 

Another source of auxins: seaweed extracts.

One surprise that popped up in my research: the much-ridiculed Superthrive contains auxins...as well as, of course, Vitamin B-1. Anyone who has tried to pore through the densely hyperbolic endorsements on a Superthrive label looking for the ingredients, well...good luck. 

However, I did find the ingredients on a 10 year-old, unused bottle of Superthrive sitting in my greenhouse. Is it the same formulation today? I don't know. But seeing how they haven't apparently changed the outside of the bottle much over the years, I have a feeling the insides are still the same.

The debate about the benefits of adding thiamine or other additives (including Superthrive) to plants still rage, with proponents citing research supporting their viewpoint.

Bottom line: The benefits of root formation contained in a bottle of Vitamin B-1 or any other additive product are the auxins, if any, that are included.  Small amounts of nitrogen can also encourage root development. Other fertilizer ingredients that might be contained do not necessarily reduce transplant shock. Putting the right plant in the right place, with healthy soil, along with the proper amount of sun, water and fertilizer, is all most gardeners need for success.