Does cinnamon kill fungus in soil?

Last updated: October 2026

Not reliably. Cinnamon (Cinnamomum spp.) contains antifungal compounds, and in lab dishes its powder stopped damping-off fungi only when it made up 8% of the growth medium.¹ The greenhouse trial behind that work coated faba bean seeds rather than dusting soil.¹ Clean seed-starting mix, disinfected trays, good airflow and careful watering are the proven ways to prevent damping-off.²

Why do people think cinnamon kills fungus?

The idea has a real chemical basis.¹ Cinnamon is the dried bark of Cinnamomum trees; Ceylon cinnamon (Cinnamomum verum) is called true cinnamon, and cassia cinnamon (Cinnamomum aromaticum) is the type most commonly sold in North America.⁷ Its antifungal constituents include cinnamic aldehyde and eugenol.¹

In laboratory dishes, cinnamon works against fungi.¹ A study that mixed 20 powdered spices into fungal growth medium found that cinnamon was among the spices with a highly significant inhibitory effect on soilborne fungi that cause damping-off.¹ A 2026 review of plant essential oils reports that cinnamon oil changes the structure of fungal hyphae and suppresses aerial mycelium.³ Lab inhibition is where the evidence is strongest, and it is also where the gap with garden use begins.^1,3

In North America damping-off pressure tracks indoor seed starting in late winter and spring, when cool, wet media favor Pythium, Phytophthora and Sclerotinia². In the Southern Hemisphere the same seed-starting window runs from about July to October.

What does the evidence show for cinnamon and damping-off?

The dose in the lab was high.¹ Complete inhibition of the major fungi tested needed powdered spice at 8% of the culture medium, or extract at 6%.¹ Extracts inhibited fungal growth more than the powders did.¹

The greenhouse test was a seed treatment, not a soil dusting.¹ Faba bean seeds were coated with spice powder or soaked in spice extract, then sown in soil deliberately infested with Fusarium solani or Rhizoctonia solani.¹ Cinnamon was one of the two spices with the highest protective effect, and the spice treatments performed similarly to a commercial fungicide seed dressing in reducing damping-off.¹ Extracts did better before seedlings emerged and powders did better after emergence.¹ The trial did not test Pythium, and it used one crop.¹

Translating lab activity into plant protection is the hard step for plant oils generally.³ The 2026 review lists compositional variability, volatility, phytotoxicity, limited persistence, inconsistent dose responses and insufficient field validation as the limits on practical use of essential oils against plant pathogens.³

What does EPA say about cinnamon as a pesticide?

Cinnamon and cinnamon oil are on the list of active ingredients allowed in minimum risk pesticides, the products exempt from federal registration under 40 CFR 152.25(f).⁴ Exempt products are not reviewed by EPA, and EPA treats label statements that imply federal review or endorsement of such products as misleading.⁵ A minimum risk listing therefore says nothing about whether a cinnamon product controls damping-off; if you use any product, follow the product label.⁵

What causes damping-off in seedlings?

Damping-off is caused primarily by fungi already present in the growing medium, and several genera are involved.² Seeds can be attacked before they emerge, which shows up as a poor stand, and emerged seedlings rot at or near the soil line, then shrivel, collapse or stay stunted.² Weak seedlings and germinating seed are most vulnerable when growing conditions are poor.²

What works instead to prevent damping-off?

Prevention rests on clean materials and growing conditions that let seedlings emerge quickly.² NC State Extension lists these steps:

• Clean and disinfect seed trays and flats, store them clean, and avoid reinfesting treated soil.²
• Use a sterilized soilless mix for bedding plants, or soil with good drainage, structure and aeration.²
• Use fungicide-treated seed with high germination where it is available.²
• Avoid overly thick stands, and sow at the proper depth and soil temperature for quick emergence.²
• Keep air moving and light intensity adequate.²
• Once damping-off appears, water less often, improve drainage and ventilation, and remove affected flats.²
• For organic growers, biological products containing Bacillus subtilis, Streptomyces lydicus, Trichoderma or Gliocladium virens are available and work best combined with these cultural practices; follow the product label.²

Does cinnamon help cuttings root?

The evidence is thin and comes from single-species trials.⁶ In a 2024 study on leaf cuttings of the succulent Prometheum sempervivoides, the highest dose of a commercial rooting hormone gave the best rooting.⁶ Cinnamon powder raised the survival of cuttings planted 24 hours after they were taken, and it outperformed aloe vera gel as a natural rooting aid.⁶ That is a modest result for one plant, and it does not show that cinnamon replaces a rooting hormone.⁶