Fluoride is detrimental to cannabis plant health and growth

Glen Johnson

Is Fluoride Hurting Your Cannabis?

January 1, 2021

Is your farm in a residential area where Fluoride is commonly added to the water supply to prevent tooth decay?

City water systems are legally allowed to dose Fluorine in the range of 1 ppm, but the toxic dose for plants is 1/5th of that amount at only 0.2 ppm.

If you think this might be affecting your farm, you may be interested in hearing some things I’ve learned recently in my own efforts to discover the potential dangers Fluoride could pose to a cannabis farm.

I recently found myself consulting for a startup farm in the commercial district in a large city. I asked to see a water test and they had one that showed incredibly clean water. However the test was missing a few key elements that can be potentially toxic to plants, so before I could sign off on the idea of skipping the installation of a very expensive RO filter system, I asked for another test that includes Boron, Potassium, Sodium, Fluorine and Copper, all of which are capable of causing nutrient lockouts if they are in excess.

The test came back with everything well below toxic thresholds – except Fluorine, which was at 0.82 ppm.

This is about 4x the tolerable amount for most plants, although there is considerable variability in the way different ages of plants, different species and different cultivars are affected. But the bottom line is that, to one degree or another, all plants are affected by Fluorine in a negative manner that stunts growth.

Digging in to see just how bad this might be, I found that if you use water containing fluoride on a consistent basis, the fluoride will build up in plant tissues — particularly the leaves — and over time it will accumulate to the point that it starts inhibiting the process of photosynthesis and causing damage to plant tissues.

Will this cause your plants to fall over dead? NO. But it’s almost worse because if there were some instant horrible damage we would immediately set about to fix the problem. With Fluorine, the damage is slow. It creeps up on you so you can’t see that it’s happening unless you do a careful side by side experiment, and even then, the difference is a percentage of diminished growth – not catastrophic death – just enough to chip away at your crops, season after season.

To see the potential for damage you can look at this Google search containing Images of Fluorine toxicity in Plants

For household plants, the most common micronutrient toxicity of all, is caused by excess fluoride.

Fluoride is an accumulativepoison in plant foliage. Accumulation may be gradual over time. Fluoride strongly inhibits photosynthesis and other processes. It will move in the transpiration stream from roots or enter as airborne particles through stomata and accumulate in leaf margins. Typical fluorine injury symptoms on broadleaf plants include marginal and tip necrosis that spread inward.
High concentrations of Fluoride in soil may seriously threaten the life of plants, devastate soil microbial activity, disrupt the soil ecology, and cause soil and water pollution.

Potential Remedies:

High calcium levels in the soil or rooting medium, such as use of dolomite, can help tie up fluoride and prevent injury.
Calcium foliar sprays can help tie up Fluoride in the leaves.
Water can be cleaned with RO filters.
Keep the water and fertilizer solution pH above 6 where Fluorine remains tied up and unavailable to plants.

Solution:

The Bone Char Filter System

Bone char is made from burning Fish or Cow bones at 500F very much like you would make BioChar.

This creates a renewable, and biodegradable, filter media that is quite cheap and uses either fish or cow bones. Searching out products that are available on the market I found a tank system that is designed to allow for user replacement of the char product after it becomes saturated. No filters to purchase!

This is the tank system which costs $1400 not counting shipping and installation. The Bone Char Media costs $500 and the system treats 450,000 gallons before you have to replace the char. The throughput is only 1.8 gpm so if this is too low for your system, you could place several of these in parallel to speed up the flow. At this rate, one unit should be able to process around a 2500 gallon tank every day. At this rate you would go roughly 225 days between media changes.

Here’s a video showing the tank system.

The following studies validate the ability of Bone Char to remove Fluorine.

Details about particle size, pH and the animal type for the char are also included.

An Evaluation of Fish Bone Char as an Appropriate Arsenic and Fluoride Removal Technology

Published Online:3 Dec 2009https://doi.org/10.1089/ees.2009.0222 View article Cost $50

Abstract:

This study evaluates fish bone char as an appropriate fluoride and arsenic removal technology for emerging regions, and investigates differences between fish bone char and cow bone char. The results… show that charring temperature affects the capacity of fish bone char to adsorb fluoride. It was found that 500°C is the best charring temperature based on removal effectiveness and residual water quality. Specific surface area is affected by charring temperature. The study also found that fish bone char can remove fluoride and arsenic simultaneously with minimal competition, albeit fluoride is removed more effectively than arsenic. Additionally, the data suggest that fish bone char is a viable option for fluoride removal in developing countries, and minor differences in fluoride removal capacity between cow bone char and fish bone char were discussed.

Adsorption of Fluoride from Water Solution on Bone Char

https://doi.org/10.1021/ie070023n PDF (219 KB)

Abstract

The effects of solution pH and temperature on the adsorption of fluoride onto bone char made from cattle bones were investigated in this work. It was found that the maximum adsorption took place at pH 3 and the adsorption capacity decreased nearly 20 times augmenting the pH from 3 to 12. This behavior was attributed to the electrostatic interactions between the surface of bone char and the fluoride ions in solution. The adsorption capacity was not influenced by temperature in the range from 15 to 35 °C. A comparison of fluoride adsorption capacities among several adsorbents revealed that the adsorption capacity of the bone char was 2.8 and 36 times greater than those of a commercial activated alumina (F-1) and a commercial activated carbon (F-400). The adsorption capacity is considerably dependent upon the physicochemical properties of the bone char surface and the solution pH.

Optimization of regenerated bone char for fluoride removal in drinking water PDF Link

Abstract
This paper presents findings of a study on optimization and application of the regenerated bone char media for the defluoridation of drinking water in Tanzania where more than 30% of all water sources have fluoride concentrations above the 1.50 mg/l which is recommended by the World Heath Organization (WHO). In this study, regeneration temperature, regeneration duration, contact time, regenerated bone char dosage and particle size were investigated. This study further indicated that the smallest size of regenerated bone char media (0.5–1.0 mm diameter) had the highest defluoridation capacity. Column filter experiments indicated that regenerated bone media is capable of removing fluoride from drinking water to meet both WHO and Tanzania recommended values.

The summary of all that info is to say that removal of Fluoride is possible with low tech, low expense and a renewable resource filter material.

On a more personal note…

This is the first time I’ve ever taken a close look at how Fluorine affects people.

My toothpaste and mouthwash products are now sitting in the trash where they belong. I can’t believe that our government (which I would like to think I could trust) has dropped the ball on this to such an extreme extent. I’m just really disappointed – again.