The Vitamin B1 Myth

Plants manufacture auxins and hormones that are used to regulate their growth.  In many instances, supplying these hormones and auxins to plants can stimulate the growth of roots, foliage, regulate internodal spacing and promote flowering and fruiting.  While these occur naturally in plants, man-made versions like NAA can produce a similar effect as those naturally occurring hormones and auxins.

Plants manufacture B vitamins: riboflavin, thiamine, and nicotinic acid. An increase in the content of these vitamins is frequently observed with an increase in the protein content of cereal grains and vegetables suggesting that these vitamins play a role in synthesis of proteins. While plants manufacture vitamins, they do not take up vitamins as these molecules far too large to pass through root membranes. Humans and some other animals rely upon dietary intake of vitamin B6 and certain amino acids which are essential in the diet as they cannot be synthesized like many other vitamins.

You can find vitamin B1 on the shelves in many garden centers.  Typical claims are that applying vitamin B1 to new plantings helps to overcome transplant shock.  Is there any truth to this claim or is this merely another horticultural myth?  Studies at the University of California, Davis conclude that there is no basis to support the claim that vitamin B1 benefits plants by stimulating root growth or reducing transplant shock as many advertisements claim.

Jeff Schalau, an extension agent with the Arizona Cooperative Extension, Yavapai County wrote: “Application of vitamin B1 (thiamine) to root systems of whole plants does not stimulate root growth.  This myth arose from early work on plant growth regulators, called auxins, which were mixed with vitamin B1. Various studies using both woody plants and annual flowers and crops failed to demonstrate that vitamin B1 treatments provide any subsequent growth response.”

Robert Cox, Horticulture Agent, Colorado State University Cooperative Extension wrote:  “Several studies using (a variety of herbaceous and woody plants) have failed to demonstrate that vitamin B1 treatments provide any type of growth response.  While root stimulator products are not necessary for transplant success, if you do use one, make sure it contains a rooting hormone and fertilizer rather than just vitamin B1.  The vitamin B1 is for marketing purposes rather than actual effect.”

An independent study to test the claim that vitamin B1 applied to plants results in better foliage or root growth was conducted by the editors of Sunset Magazine. The results of the study were published in the magazine.  Starting with fast growing bedding plants, six different treatments were used:

  • B1 alone
  • B1 with phosphorous
  • B1 with 3-10-3 fertlizer
  • B1 with 10-10-10 fertilizer
  • 10-10-10 fertilizer alone
  • Plain water

The results at two weeks showed new leaves and growth on all plants except those given vitamin B1 alone.  The B1 only plants showed no growth at all.  The plants in treatment 5 (fertilizer alone) were blooming after four weeks.  Those receiving B1 with fertilizer (treatments 2, 3 & 4) took two more weeks to bloom.  After six weeks, fertilized plants had better color, more blooms and more foliage.  The shocking conclusion:  Plants that received only water out performed those receiving solutions treated with B1!  Lesson: stick with water and nutrients.  Skip vitamin B1.

As a result of in-house testing of vitamin B1, Almaden Valley Nursery, a retail garden center, pulled vitamin B1 products from their retail shelves, refusing to subject their customers to another snake oil product.  These studies should convince you that proper nutrition applications are the best bet for healthy plants.

What can you do to promote root growth?

For propagation of vegetative cuttings or promoting root growth when transplanting, there are effective options.  IBA (Indole-3-butyric acid), IAA (Indole-3- acetic acid) and NAA (1-Naphthalene acetic acid) are auxins that stimulate root growth. Some B1 products contain one or both of these auxins which will be beneficial when transplanting.  One “Super …” product consists of NAA and B1 despite claims on the label that it contains more vitamins and hormones than exist in nature. It is the NAA that provides benefits. B1 provides only color and scent!

NAA is particularly effective in inducing root growth on cuttings because its primary effect is to enhance lateral root growth rather than primary root growth.  However, NAA, like IBA suppresses top growth of plants and, therefore, should not be used on a continuing basis.  One or two applications after transplanting rooted cuttings or other plants into new containers or the ground will suffice to promote lateral root growth.  The plant can take over from there with its naturally generated hormones and auxins. For optimum results, insure that your plants are receiving complete nutrition*, adequate water and proper levels of light.

Dyna-Gro® KLN Concentrate and Root-Gel® contain both IBA and NAAand are very

effective for vegetative propagation and stimulating root growth at any time. KLN Concentrate is most effective on herbaceous cuttings in general while Root-Gel® is often more effective for more difficult to root, woody cuttings. In addition, Dyna-Gro® Pro-TeKt®: The Silicon Solution® has produced 100% success rate in rooting vegetative cuttings without the application of any auxins or hormones.  Combined with KLN Concentrate, the two are even more effective used as a drench into the rooting medium before or after sticking the cuttings.