Just scratching the surface of this yet and have not tried it myself, but I came across this info on a french iris forum, so just thought I should pass it along. I then got a link from there to an article about cactus culture, https://www.cactuspro.com/arti... (in french, scroll down some to see the part about cinnamon).

I've started to search a little about the subject and it seems cinnamon and cinnamon oil has gone through some scientific testing when it comes to potato tubers and soft rot.

Various methods of application from dusting the cuts with cinnamon, soaking tubers (rhizomes for us) in it, spraying foliage as a preventative, watering soil and so on. I don't think it works simply mixing cinnamon powder with water, but I could be wrong about that. The cactus article suggested using acetone as a solvent. Some of the scientific potato articles I've seen suggested ethanol.

As I said, I haven't tried this, but would love to find out more . Maybe someone has already tried this?

Like all other types of bark, cinnamon contains anti-fungal substances and cinnamon on seedlings (never tried it with iris seedlings) that are prone to damping-off is a time-tested method and I have used it with success.

Cinnamon is also believed to have other beneficial effects on plants:
https://www.gardeningknowhow.c...
http://www.sun-gazing.com/spri...

Cinnamon and other spices on seedlings:
http://theadventurebite.com/da...

I was told by a fellow NGE member to sprinkle cinnamon on Dahlia bulbs to prevent rot, but I hadn't thought about it for irises.

That would make them smell good enough to eat!

William and Lilli ~ for sharing that information regarding cinnamon and other natural ingredients for their fungicidal properties. I have previously used it on growing seedlings in winter, but had not thought about using it for irises.

Another thing I have used on growing seedlings in the winter under lights is chamomile tea. I never thought to use it in the iris beds....

https://www.gardeningknowhow.c...

I've filed this cinnamon info away in case of rot! Thanks.

Interesting information! Thanks for the links.

Interesting information, but maybe no ethanol on the rhizomes!

In the very small concentrations we are talking about here, where you only use the ethanol as a solvent for the cinnamon and then dilutes this with water, I don't think it will be dangerous for the rhizomes. But when in doubt, always try it on a very small scale first. I wouldn't personally want to spray directly in strong sun either.

That said I'm still looking for a really good recipe for a spray. I'm concerned that the spray in the French link might have a too low cinnamon content in the prepared solution as compared to the more scientific papers, but on the other hand I use google translate on it, so might be something else that I misunderstand.

However I might have found a few more interesting recipes and in English this time. It seems cinnamon have some popularity among orchid growers: http://firstrays.com/free-info...

One of those recipes use rubbing alcohol and another uses hot water to make a spray.
I'm sort of inclined to try the rubbing alcohol one, but add some water to the mixture. Thoughts?

Another very interesting idea is the one to mix cinnamon powder with a casein-based glue (Elmer's) or cooking oil to make a thick paste.This would then have some water resistant properties, which certainly would be welcome in rainy weather.

As the recipe in the above link is using rubbing alcohol, it seems proper to highlight that not all rubbing alcohols are the same.
Over here most seem to use ethanol, instead of the the isopropyl based that is assumed in the above recipe. One needs to check this carefully!

Using ethanol at full strength on plants probably isn't a great idea, although I have seen some sprays mentioned for plant use that have 20-30% ethanol in them, so this can still be worth exploring. Unfortunately I'm not able to post a link to the Pdf involved, but this was part of a trial to see if ethanol can be as beneficial to plants as methanol. Methanol sprays is supposed to increase yields on some plants, but of course methanol is toxic to humans so ethanol would be safer to use.

You can even water your plants with alcohol and provided you don't use to much it will be okay. It is supposed to give shorter stems on some forcing bulbs.

This is not really a link I ever anticipated posting, but if you like to know more about the effect of alcohol on plants, you can read some here:
https://sciencing.com/effect-a...

I just sprinkle the powdered cinnamon directly on top of the soil and never water the seedlings from the top - which is always a good idea with plants that are prone to dampening-off.

...... the active component of cinnamon, which has the main fungicidal action is the phenylpropene compound, Eugenol, plus the co-activity of a number of other essential oils in much smaller concentrations. Cinnamon is a member of the Lauraceae family, many members of which have the same compound plus numerous other essential aromatic components.

Cinnamomum: cinnamon, cassia and camphor laurel
Laurus: bay laurel
Persea: avocado

Also the Myrtle family contains the same bio compounds of which Clove is a member of.
There are already a number of products on the market that utilize Eugenol as a insecticide, miticide, and acaricide, and it shows some bio activity towards certain pathogenic fungi
some more info here:
https://www.naturepest.com/clo...

thank you for that article, timothy. makes a lot of sense. i remember the dentist packing a clove scented gauze, and we used cinnamon in the kitchen where i worked, to discourage ants in the microwave. only problem was that we couldn't get some of that brn/reddish stain (leftover powder) in the seams of (edited to correct typo) the microwave oven.

Excellent info about about the Eugenol, Timothy. It will make it much easier to search for more info on the subject as well.

I especially noted the efficiency against Botrytis cinerea, which I found very interesting. Botrytis is big problems for my lilies, so would be worth trying this to see if it was better than the baking soda spray I currently use or perhaps one can even combine the two or alternate between them.

Now if Eugenol could prove to be efficient on iris leaf spot as well, that would have been awesome.

Edit: spelling

Timothy!

IrisLilli said: Timothy!

Another from me too!

Some experimenting.

I let a tablespoon of cinnamon soak in 3 tablespoons of 85% rubbing alcohol for several days. This was mostly ethanol but also had a small amount of isopropyl alcohol in it. I filtered it and added a tablespoon of this mixture to a liter of water, added a teaspoon of baking soda and 1/2 teaspoon of dish washing liquid(to help the spray wet the waxy foliage better) and 1/2 teaspoon of liquid soap.

I sprayed this solution on Maui Moonlight, Ask Alma, Seraphita, 3 smaller rhizomes of Dangerous Mood and 3 rhizomes of Red zinger(near my boiler room entrance). I also tried this on the lily Robina and my most easterly plantings of the lily Whistler. I will be checking these for any bad reactions before proceeding any further.

My hope is then that this will be somewhat preventive to leaf spot on irises and Botrytis cinerea on lilies and also of course work preventative against bacterial soft rot. Baking soda has some effect on Botrytis cinerea on lilies and is supposed to help with leaf spot on irises, but I'm uncertain of what dose to use for irises. More baking soda should have better effect, but can also burn leaves.

To mix cinnamon and baking soda together is rather experimental and I do not know what the effect will be, so nothing I recommend, just want to inform anyone interested that I'm testing it.

interested in your results, william.

have you tried ground cinnamon sprinkled directly on the rhizomes? iif anyone else has, i would be interested in learning of the results.

Yes, I have tried sprinkling cinnamon directly on the rhizomes, but I have no real opinion if it is effective or not, as I only done it a few times and it was not very serious, as I still relied on bleach to sanitize the rhizomes. Based on what I read about rot preventing in potatoes I'm thinking one would probably need to apply cinnamon before rot becomes an issue, as a preventive measure. I don't believe it is a cure. Without intentionally attempting to infect rhizomes, and having a control group, it would also be very difficult to properly measure effectiveness, but infecting rhizomes on purpose is not for me!