How do I prevent and treat mold on microgreens?
Mold is the most common and destructive problem in microgreen growing, caused by excess moisture, poor airflow, high temperatures, contaminated seeds, and overcrowding. Species like Rhizopus, Mucor, Aspergillus, and Penicillium thrive in the warm, humid conditions microgreens need. Prevention through environmental control, sanitation, and proper technique is far more effective than treatment. Sunflower, pea shoots, wheatgrass, basil, and cilantro are the most mold-susceptible varieties.
- Control airflow, humidity, and temperature to prevent mold environmentally5
Environmental control is the single most effective mold prevention strategy. Mold requires three things to grow: moisture, warmth, and stagnant air. Remove any one of these and mold cannot establish.
📌 diy📌 free2/11/2026, 1:25:05 AM
🛠️ Small oscillating or clip-on fan, thermometer, hygrometer
- Identify mold vs. root hairs and know common mold species5
Before treating mold, confirm it is actually mold. The most common false alarm in microgreen growing is confusing healthy root hairs with mold. Knowing which mold species you are dealing with also helps determine the right response.
📌 best practice2/11/2026, 1:28:11 AM
🛠️ Spray bottle with water (for the water test)
- Sanitize trays and equipment between every growing cycle4
Reusing contaminated trays is a leading cause of recurring mold. Fungal spores survive on plastic surfaces between cycles and re-infect new plantings. Clean and sanitize trays after every harvest.
📌 diy📌 best practice2/11/2026, 1:25:49 AM
🛠️ Bleach or hydrogen peroxide, scrub brush, basin for soaking, trays
- Choose the right growing medium to minimize mold risk4
The growing medium directly affects moisture retention, drainage, and pathogen load. Different media have very different mold profiles, and switching medium can solve chronic mold problems.
📌 best practice2/11/2026, 1:26:24 AM
🛠️ Growing medium of choice (coconut coir, hemp mats, BioStrate, or soil), trays
- Use proper seeding density and bottom watering to prevent mold5
Overcrowding and top-watering are two of the most common causes of mold in microgreen trays. Correct seeding density allows airflow between plants, and bottom watering keeps the leaf canopy dry.
📌 diy📌 free2/11/2026, 1:27:14 AM
🛠️ 1020 trays with holes, 1020 solid bottom trays, spray bottle
- Try DIY antifungal remedies: cinnamon, chamomile tea, GSE, and diatomaceous earth3
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.
📌 diy📌 free2/11/2026, 1:27:45 AM
🛠️ Cinnamon powder, chamomile tea bags, grapefruit seed extract, food-grade diatomaceous earth (all optional)
- Use OMRI-listed biofungicides for organic mold prevention4
Several OMRI-listed (Organic Materials Review Institute) biological and natural fungicides are approved for use on food crops and provide effective mold control without synthetic chemicals. These products are suitable for commercial growers selling organic microgreens.
📌 commercial2/11/2026, 1:26:50 AM
🛠️ OMRI-listed fungicide of choice, sprayer or drenching equipment, PPE
- Use hydrogen peroxide spray to treat active mold on microgreens4
Food-grade hydrogen peroxide is the safest and most widely recommended treatment for active mold on microgreens. It kills mold on contact, breaks down into water and oxygen, and leaves no harmful residue on edible plants.
📌 diy📌 free2/11/2026, 1:25:26 AM
🛠️ 3% food-grade hydrogen peroxide, spray bottle, measuring spoons
- Sanitize seeds before planting to eliminate mold spores5
Most mold problems originate from spores already present on the seed coat. Pre-treating seeds -- especially large seeds like sunflower, pea, and cilantro -- dramatically reduces mold outbreaks. Multiple methods exist ranging from free DIY to commercial products.
📌 diy📌 free2/11/2026, 1:24:37 AM
🛠️ 3% food-grade hydrogen peroxide, bowl for soaking, strainer, measuring spoons
- Use ZeroTol 2.0 or OxiDate 2.0 for commercial-grade mold control5
BioSafe Systems makes the two most widely used commercial fungicides for microgreen growers: ZeroTol 2.0 and OxiDate 2.0. Both use hydrogen peroxide combined with peroxyacetic acid to kill mold, bacteria, and algae on contact with zero residue and no pre-harvest interval.
📌 commercial2/11/2026, 1:24:15 AM
🛠️ ZeroTol 2.0 or OxiDate 2.0, spray bottle or sprayer, measuring tools