How To Start Seeds Indoors Under Lights (COMPLETE GUIDE) — Key Takeaways
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How To Start Seeds Indoors Under Lights (COMPLETE GUIDE)
Epic Gardening30mMar 7, 2026
Watch the originalPlant two seeds per cell (not one) to statistically guarantee germination, and position your grow light as close as possible to the soil surface without burning seedlings — insufficient light is the single most common failure point.
Key takeaways
Soil temp above 70°F halves tomato germination time
Soil temp above 70°F halves tomato germination time
- At 60°F soil temp, tomatoes take ~15 days to sprout; above 70°F, they sprout in 7–9 days.
- Use a heat mat only until most seeds have sprouted — after that, heat is no longer critical.
Fertilize with dilute liquid organic feed starting at week 2
Fertilize with dilute liquid organic feed starting at week 2
- FoxFarm Grow Big dose: 0.5 tsp per gallon once per week; apply every watering session (every 2–3 days) via bottom-watering after the 2-week mark.
- Seed leaves yellow at ~2 weeks because the plant exhausts their stored energy — fertilizer replaces that depleted food source.
Run an oscillating fan 6–8 hrs/day once seed leaves appear
Run an oscillating fan 6–8 hrs/day once seed leaves appear
- Wind triggers thigmomorphogenesis — plants respond by building thicker, sturdier stems that survive outdoor conditions.
- Fan increases evaporation, so water more frequently; keep it close enough to move all seedlings but not so strong it desiccates soil.
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In this video
- 1mIntroduction: Why start seeds indoors?
- 1mEssential materials for seed starting
- 2mSelecting and preparing the growing medium (soil)
- 3mTechniques for filling trays and compressing soil
- 4mPlanting guide: Variety-specific tips and rules of thumb
- 5mTomatoes
- 7mOnions
- 7mLarge seeds
- 10mCompound seeds
- 12mHerbs
- 16mSensitive roots: Transplanting beans and peas
- 18mPost-planting care: Watering techniques
- 19mLighting requirements: Intensity and duration
- 21mUsing heat mats to speed up germination
- 23mBoosting seedling vigor and "seed leaves"
- 23mUsing fans for environmental conditioning
- 25mFertilizing seedlings at the two-week mark
- 27mHardening off seedlings for outdoor transplanting
- 28mPotting up: When and how to move to larger containers
- 30mSummary and conclusion
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