Deciphering fact from fiction about plant care can be challenging for even the most seasoned gardener. Misinformation about natural remedies or cures for plant diseases can spread like wildfire, making it difficult to decide on a treatment method for your sick plants.
One common myth is applying cinnamon to the soil surface to cure a plant with root rot.
It’s easy to see how a myth like this could start; cinnamon has inherent antifungal properties.
Many studies have proven that when cinnamon oil or powder is applied directly to a fungus in a sterile environment, it stops the growth of the fungus. Many essential oils like clove, oregano, or mint also stop the growth of fungi in a sterile environment where they are applied directly to a fungus.
Cinnamon powder has also been shown to treat post-harvest diseases like Botrytis cinerea, which is a common mold that you’ve probably seen growing on those strawberries or leftovers you forgot about in your fridge.
The key to cinnamon’s antifungal property is that it must directly contact the body of a fungus.
That means that you must apply the cinnamon directly to the white fuzzy body of a fungi for it to work. With root rot, the body of the fungus is on the roots underneath the soil, so dusting cinnamon on the surface of the soil will have no effect.
Cinnamon often can have the opposite of the intended effect and damage delicate root systems of plants like orchids. Many essential oils can damage sensitive tissues in humans, too, so always be sure to use products only for the purpose they’re intended, and follow all label directions.
Treating root rot should instead focus on the causes of the disease. Most of the time root rot is caused by overwatering. When creating a watering plan, remember to let plants dry out a little in between waterings. Many plants like to dry out and allow their roots to breathe. When they are kept constantly wet, the roots are not exposed to air and can’t perform cellular respiration. The roots become weakened and begin to die as root rot begins.
If you have a potted plant, make sure its pot has a drainage hole and adequate drainage. CSU Extension’s Plant Talk article number 1318 at planttalk.colostate.edu can help you determine the right watering plan for your houseplants.
It’s true cinnamon can be a useful treatment in some cases. Scientific studies have shown cinnamon is an effective treatment for post-harvest diseases like the ones you might find in your fridge and the disease Sclerotinia, which grows on the surface of the soil and on stem surfaces can be treated by the application of cinnamon oil. However, commercial fungicides or preventative measures are more effective in these cases.
For more information on this and other topics, visit extension.colostate.edu or contact your local CSU Extension Office.
Tommy Roth is the CSU Extension Boulder County Home Horticulture Coordinator.
