Sanitize trays and equipment between every growing cycle

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.

Step-by-Step Process

1. Remove all soil/medium and root debris immediately after harvest
2. Scrub trays with warm soapy water and a brush to remove organic residue
3. Rinse thoroughly with clean water
4. Sanitize using one of the methods below
5. Air dry completely before storing or replanting -- moisture on stored trays breeds mold

Bleach Solution (Gold Standard for Health Departments)

• Concentration: 1 tablespoon of household bleach per 1 gallon of water (approximately 50-200 ppm)
• Soak time: 15-20 minutes
• Rinse thoroughly with clean water after soaking -- bleach residue can harm seedlings
• Approved by most health departments for commercial food operations
• Do not exceed 200 ppm -- higher concentrations leave toxic residue and damage plastic over time

Hydrogen Peroxide Solution

• Concentration: 3% hydrogen peroxide diluted 1:10 with water
• Soak time: 10-15 minutes
• Environmentally safer than bleach (degrades to water and oxygen)
• No rinsing strictly required, though rinsing is good practice
• Preferred by many commercial microgreen growers

Vinegar Solution

• Concentration: 1:1 white vinegar to water
• Application: Spray on trays, let sit for 10 minutes, then rinse
• Can be followed with a hydrogen peroxide spray (applied separately, not mixed) for enhanced effectiveness
• Less effective than bleach or H2O2 for killing spores

Commercial Sanitizers

• SaniDate 5.0 (BioSafe Systems): Hydrogen peroxide + peroxyacetic acid based; OMRI listed; effective at 40 ppm for pathogens; no residue, not pH dependent; can also be used for produce washing and irrigation water treatment
• Physan 20: Use 1.5 tablespoons per gallon for hard surface disinfection; very concentrated -- measure precisely, never estimate
• ZeroTol 2.0: 1:100 dilution for pre-cleaned surfaces
• Contact your local health department for approved sanitizers in your jurisdiction -- requirements vary by county, state, and region

Equipment Beyond Trays

• Sanitize scissors/knives, spray bottles, and any tools that contact plants
• Clean shelf surfaces and growing racks monthly
• Replace spray bottle nozzles periodically -- they harbor biofilm

Tips

• Dedicated trays for mold-prone varieties (sunflower, pea) prevent cross-contamination
• Heavy-duty 1020 trays (Bootstrap Farmer, Bootstrap Farmer Extra Strength) last hundreds of cycles when properly maintained
• If trays develop staining or rough texture that cannot be scrubbed clean, replace them -- rough surfaces harbor spores in micro-crevices
• For commercial operations, document your sanitation SOP for food safety audits