Indoor Seed Starting

Starting seeds indoors for an early growing season head start.

Why Start Seeds Indoors?

Starting seeds indoors gives you a head start on the growing season. It is especially valuable in regions with short summers, allowing you to grow heat-loving crops like tomatoes, peppers, and eggplants that need a long growing period.

When to Start Seeds Indoors

Timing depends on your last frost date and the specific crop. Generally:

  • 6-8 weeks before last frost: Tomatoes, peppers, eggplant
  • 4-6 weeks before last frost: Squash, cucumbers, melons
  • 8-10 weeks before last frost: Onions, leeks, celery
  • 10-12 weeks before last frost: Lavender, rosemary, some flowers

Equipment Needed

  • Seed-starting trays or small pots (72-cell trays work well)
  • Sterile seed-starting mix (not garden soil)
  • Labels and marker
  • Humidity dome or plastic wrap
  • Heat mat (optional, for warm-season crops)
  • Grow lights or sunny south-facing window

Step-by-Step Process

  1. Fill containers: Moisten seed-starting mix until damp. Fill cells or pots to within 1/4 inch of the top.
  2. Plant seeds: Follow depth guidelines on seed packet. Generally, plant at 2x seed diameter depth.
  3. Label immediately: Write variety name and date on each cell or row.
  4. Water gently: Mist with spray bottle to settle seeds without displacing them.
  5. Cover with dome: Place humidity dome on top to maintain moisture.
  6. Provide warmth: Place on heat mat or warm surface (70-75┬░F for most seeds).
  7. Check daily: Remove dome once seeds germinate to prevent damping off.
  8. Add light: Place under grow lights 2-3 inches above seedlings for 14-16 hours daily.

Caring for Seedlings

  • Water from bottom: Place trays in water-filled saucers to encourage deep root growth.
  • Fertilize: Once true leaves appear, feed with dilute liquid fertilizer (quarter strength).
  • Air circulation: Gentle fan for 30 minutes daily strengthens stems.
  • Thin if needed: Remove weak seedlings, leaving strongest per cell.
  • Hardening off: Gradually expose to outdoor conditions over 7-10 days before transplanting.

Common Problems

  • Leggy seedlings: Insufficient light ΓÇö move lights closer or add more hours
  • Damping off: Fungal disease from overwatering ΓÇö improve air circulation
  • Slow germination: Temperature too low ΓÇö use heat mat
  • Mold on soil: Reduce watering, increase ventilation

Applies to