Cinnamon – Does it Stop Damping Off in Seedlings?

Cinnamon is commonly used by gardeners to prevent damping off in seedlings but does it really work? Lots of people claim that it does, but I can’t find any scientific studies that use cinnamon in the same way as gardeners, but there is evidence that it might work.

There is also an issue about which cinnamon should be used. There is the real or true cinnamon and the fake cinnamon. Which one, if either, stops damping off?

I spent quite some time reviewing the information and this subject is a lot more complex than I had originally thought. Here are the spicy details about cinnamon and damping off.

What is Damping Off?

Gardeners talk about damping off as if it is one disease that affects seedlings, but in fact it is many  different diseases caused by different fungi. To the casual gardener, they just happen to all have similar symptoms. The lower stem of new seedlings gets thin, and the seedling falls over and dies.

Damping off is not really a disease. It is better to think of it as a symptom of many diseases – it describes what happens to the seedling. Several fungi can cause this problem, including species of rhizoctonia, fusarium and phytophthora. The most common culprit is the soil fungus pythium.

Gardeners usually use the dry powdered cinnamon, and sprinkle it on the newly germinated seedlings in the hopes that it stops damping-off.

More Information on Damping-off here.

What is Cinnamon?

That probably seems like an odd question to ask, but the answer is much more complicated than you think.

Cinnamon is a powder that is formed by grinding bark from a number of different trees in the genus Cinnamomum. This genus contains over 300 species and at least 4 or 5 are used to make cinnamon.

Many websites talk about the true cinnamon and compare it to the fake cinnamon, but in reality they are several so-called fake ones and two different species names are referenced for the real stuff.

The true cinnamon, also called Sri Lanka or Ceylon, is reported to be produced from C. zeylanicum or C. verum. But these are the same species. C. verum is the currently accepted name and C. zeylanicum is a synonym.

The fake cinnamon is usually called cassia or Chinese and many sites make it sound as if cassia is a completely different type of plant. Cassia is a common name used to refer to Cinnamomum aromaticum and Cinnamonum cassia. These last two plants are the same species and scientists have not agreed on which is the correct name. I’ll go with The Plant List and call it C. cassia.

Hold on a minute. There are more fake cinnamons.

• C. burmannii, the Indonesian cinnamon
• C. loureiroi, the Vietnamese cinnamon
• C. citriodorum, the Malabar cinnamon
• C. tamale, the Indian cinnamon

Cinnamon is also produced from an unrelated species, Canella winterana.

The problem we have is that, in North America at least, almost all types are just called cinnamon. We do not distinguish between them, unless it is the true Ceylon cinnamon. This latter one is much more expensive, and it is usually labeled correctly to justify the higher price.

Which cinnamon stops damping-off? Since most reports from the general public just say cinnamon, we don’t really know which one they used.

What Does the Science Say?

The antifungal and antimicrobial properties of cinnamon have been studied and confirmed. At least one of the active antifungal  components, cinnamaldehyde, has been well studied and there is some understanding about how it controls fungi at a chemical level.

Unfortunately, for several reasons we can’t conclude from these studies that cinnamon, as used by gardeners, controls damping-off. Here is why.

Type of Cinnamon Studied

Several studies do not specify the name of the species tested and in most cases only a single species was used. I even found one study that used a species that is not commonly used to make commercial cinnamon.

One study did compare the essential oils of several species and found that all of them had some antifungal properties, but some were much more effective than others. The true cinnamon, C. verum, was the most effective.

Form of Cinnamon Used

Studies have used four forms of cinnamon; dry powder, aqueous (ie water) extraction, alcohol extraction and commercial essential oil. The latter two forms have been studied the most, probably because they contain the highest levels of organic compounds.

Aqueous, essential oil (second study) and alcohol extracts all showed antifungal properties. Essential oils are more effective than alcohol extracts, probably because the active ingredients are more concentrated. It is reasonable to expect that aqueous extracts are the lest effective.

One study mixed the powder with soil and found some effects. I found no study that sprinkled the dry powder on the surface of the soil, which is the common method used by gardeners.

Fungi Being Studied

A wide range of fungi were studied; many have nothing to do with damping-off. Although a few damping-off species were tested using either alcohol extractions or essential oils (ref 2), none were tested with dry powder.

Not surprisingly, the effectiveness of cinnamon to control fungi varied by species.

In vitro Testing

Many of the studies were in vitro tests that simply looked at the effect of cinnamon on fungi growing in petri dishes. No soil or seedlings were involved. These tests clearly show antifungal properties but they can’t be extrapolated to conclude that similar results would be obtained with potted seedlings.

Commercial Products

Most commercial products for damping-off contain synthetic fungicides and these products probably work well.

I did find one product, Cinnamite, that contained cinnamaldehyde, which is the known active antifungal agent in cinnamon, but the product is labeled for use against mites, aphids and powdery mildew, but not against damping-off.

Conclusion

All forms of cinnamon seem to suppress a wide range of fungal species including those that cause damping off. The true cinnamon is more effective than the fake cinnamons. Essential oils are more effective than other forms of extract.

Gardeners sprinkle the powder onto seedlings or the surface of the soil. Watering these would create aqueous extracts, but nobody knows if the amount of active ingredient in these extracts would be enough to reduce the growth of damping-off fungi.

There is a lot of anecdotal evidence, but we all know the value of that. I doubt that very many gardeners have used controls, which means their conclusions are meaningless.

If you are going to use a spice to treat damping-off, cinnamon is your best choice. It probably works to some extent, but there is no direct scientific evidence that it will prevent damping-off in seedlings.

References:

1. Difference Between True and Fake Cinnamon; https://www.healthline.com/nutrition/ceylon-vs-cassia-cinnamon#section6
2. Antimicrobial and Antifungal Activities of Spices; http://www.mdpi.com/1422-0067/18/6/1283/pdf
3. Cinnamaldehyde and its Derivatives, Antifungal Agents; https://www.ncbi.nlm.nih.gov/pubmed/27259370
4. Image Source for cinnamon: Cinnamon Vogue
5. Image of damping-off; INAKAvillasge211