Try DIY antifungal remedies: cinnamon, chamomile tea, GSE, and diatomaceous earth

Several household and natural products have antifungal properties and are commonly recommended in grower communities. The evidence varies from strong to weak -- here is what the research actually shows for each.

Cinnamon Powder

What growers claim: Dusting cinnamon on soil surface prevents mold and damping-off.

What research shows: - Lab studies (published in European Journal of Plant Pathology, 2019) confirm cinnamon water filtrates inhibited fungal mycelium growth by 54.4% at 0.5% concentration and 81.4% at 1% concentration - Cinnamon powder applied as seed dressing showed significant efficacy against damping-off caused by Rhizoctonia solani and Fusarium solani - True cinnamon (Cinnamomum verum) is the most effective species - Alcohol extractions and essential oils are far more effective than dry powder

The gap: These studies used controlled lab conditions with specific cinnamon preparations, very different from sprinkling grocery-store cinnamon on soil. No direct scientific evidence confirms the home garden method works at the concentrations growers typically use.

If you want to try it: Dust a thin layer on the soil surface after planting. Use true Ceylon cinnamon if possible. It likely provides some benefit but should not be your primary defense.

Chamomile Tea

What growers claim: Brewed chamomile tea prevents damping-off when used to water seedlings.

What research shows: - Chamomile contains antifungal compounds: apigenin, bisabolol, and chamazulene - These compounds disrupt fungal cell membranes and inhibit spore germination - Lab studies show suppression of fungal growth - Anecdotal reports from experienced growers suggest it performs comparably to chemical fungicides in some cases

The gap: Making tea is not an efficient way to extract active compounds. Field evidence is observational, not controlled. Cannot reverse advanced damping-off or overcome chronically wet, cool conditions.

If you want to try it: Brew a strong chamomile tea (2-3 bags per cup), let cool completely, use as a soil drench or misting spray. Apply preventatively, not as a cure. Best used as part of a broader strategy alongside airflow and moisture control.

Grapefruit Seed Extract (GSE)

What growers claim: GSE drops in water prevent mold on microgreens and wheatgrass.

What research shows: - Contains naringin and limonin which disrupt fungal cell membranes, bind to cellular proteins, and prevent growth - True Leaf Market sells GSE specifically marketed for microgreen mold control - Some lab studies show antifungal properties

The controversy: Multiple studies have found that the antimicrobial activity of commercial GSE products may actually come from synthetic preservatives (benzethonium chloride, methylparaben) added during manufacturing, not from the grapefruit seed itself. The scientific evidence for pure GSE is weak.

Dilution ratios commonly used: - Seed soaking water: 10 drops per cup of water - Mold treatment spray: 8-10 drops per gallon of water - Preventative mist: 10 drops per cup of water

Food-Grade Diatomaceous Earth (DE)

What growers claim: Sprinkling DE on soil surface absorbs moisture and prevents mold.

What research shows: - DE is highly absorbent and reduces surface moisture - Does not directly kill mold -- it works by moisture control only - Primarily effective as a pest deterrent (fungus gnats, etc.) - Can be mixed into soil at 15-20% by volume to improve drainage and water distribution

If you want to try it: Use only food-grade DE (not pool-grade). Dust a thin layer on the soil surface. Most useful as a supplementary measure, not a standalone mold solution. OMRI-listed brands are available (e.g., Harris Food Grade DE).

Tips

• None of these DIY remedies are as reliable as hydrogen peroxide, proper airflow, and moisture management
• They work best in combination with good practices, not as replacements
• Evidence is strongest for cinnamon (lab-confirmed antifungal compounds) and weakest for GSE (may be preservatives, not grapefruit)
• All of these are food-safe and low-risk to try -- the worst case is they don't work