Free Microgreens Seed Density Calculator
Calculate precise seeding weights in grams, blackout days, light cycle duration, and expected harvest yield for standard 1020 and 1010 trays.
🌿 Variety & Tray Selection
📊 Recommended Seeding Weight
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The Science of Microgreens Seeding Density
Finding the sweet spot for seed density is the single most critical factor in profitable microgreen farming. Under-seeding results in sparse, floppy stems that collapse on harvest. Over-seeding suffocates airflow at the soil line, encouraging damping-off mold (Pythium) that can wipe out an entire rack overnight.
Weighted Blackout Stacking
Large seeds like Sunflower and Pea benefit enormously from a weighted blackout stack (placing a 10-15 lb paver or brick on top of stacked trays for the first 3-4 days). The downward physical pressure forces roots deep into the media and produces thick, uniform, upright stems.
Mucilaginous Seeds: Never Pre-Soak
While hard seeds like sunflower and peas require an 8-12 hour cold soak, never soak mucilaginous seeds like Arugula, Basil, or Chia. The moment they contact water, they exude a sticky gel coat that prevents even spreading. Sow them completely dry.
Frequently Asked Questions
Why do my sunflower microgreens have seed hulls stuck to the leaves?
Seed hulls stick when the germination humidity is too low or when the trays weren't stacked with enough weight. Keeping a moist paper towel or humidity dome during early blackout softens the shells so the growing cotyledons can shed them cleanly.
How many grams of broccoli seeds should I plant in a 1020 tray?
Standard commercial recommendation is 25 to 30 grams of dry broccoli seeds for a 1020 tray. Seeding heavier than 35g leads to dense foliage where mildew easily takes hold.
What is the difference between white root hairs and mold?
Healthy microgreen seedlings produce microscopic white root hairs that look like fuzzy fuzz along the taproot. True mold forms a spiderweb-like gray or blueish network that bridges across multiple stems, feels slimy, and smells sour.