JoAnne Skelly: Fact or fiction: Cinnamon helps your plants

JoAnne Skelly

JoAnne Skelly

Recently, I read something about powdered cinnamon and possible uses as a pest repellant, fungicide, and more.
Gardeningknowhow.com had an article which claimed that cinnamon could be used to deter ants in a home or greenhouse because “Ants don’t like to walk where cinnamon powder lays…” Another claim is that cinnamon works as a rooting compound, stimulating root growth. In addition, cinnamon can be used as a fungicide for damping off disease. It’s also supposed to stop mushrooms growing in planters, compost or mulch.
Years ago, I read research reporting that ants can be killed using talcum powder. The ants would get the powder all over them by walking through it and carrying it back to their nest. The powder prevented them from absorbing water through their exoskeleton causing the ants to dry up and die. Perhaps the effect is the same with cinnamon.
Morningchores.com claims cinnamon discourages the fungal disease known as rust, when it is sprinkled on the soil at planting. Also, that cinnamon can “heal plant wounds.” It is supposed to repel rabbits, mice and rodents by confusing their “scent instincts.” The author writes that it “Prevents mosquitos.” She states it can be used effectively on houseplants as well although I would worry about it burning the leaves. She does report that there is no scientific evidence to support the claims that cinnamon is beneficial to plants, just anecdotal evidence, but that cinnamon can’t harm anything either, which isn’t necessarily true.
Plants do not have the ability to “heal” wounds. If pruned properly, they compartmentalize the wounded area closing it off. That is not healing. I’m willing to try cinnamon in the ground squirrel holes going under the house. The smell would be much better than mothballs! I wonder if it would deter cats from using flower beds as a litter box. I don’t know how putting cinnamon on the soil prevents mosquitos.
There is research to support some of the claims about cinnamon, primarily its oils. The National Library of Medicine in an article (Kowalska, J. et al. August 31, 2022. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8433798/) reviewing research on cinnamon, says that “due to its antibacterial and pharmacological properties, it can be used in processing, medicine and agriculture.” Researchers reported that “Cinnamon acts on pests mainly as a repellent, although in higher doses it has a biocidal effect and prevents egg-laying.” Cinnamon oils and extracts do “hinder bacterial and fungal growth…” Because it can, in some cases and quantities, also injure plants, it may be a possible herbicide. “It can be used in organic farming as a promising alternative to chemical pesticides for use in plant protection…”
If you decide to try powdered cinnamon, to avoid burning plants it may be best to apply it only to soil, not directly onto leaves. Beware. Do not breath in cinnamon, because it can burn nasal and lung passages.
JoAnne Skelly is an Associate Professor & Extension Educator Emerita University of Nevada Cooperative Extension. Email skellyj@unr.edu

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