Starting Seeds Indoors Under Lights

Light is the single most important factor when you are starting seeds indoors before the last frost. Without high-intensity, localized lighting, seedlings will stretch toward your windows in a desperate, spindly reach that leaves them weak and prone to falling over. Done well, indoor seed starting gives you a month or more of a head start on your growing season, resulting in sturdy, compact starts that transplant with minimal shock. Setting up a dedicated station—even a small one—removes the guesswork from germination. By controlling the light duration and proximity, you turn a passive windowsill hobby into a reliable production line. The goal is to replicate the intensity of the summer sun in a controlled, indoor environment, ensuring your plants develop thick stems and deep green foliage from day one.

  1. Choose the Right Light Source. Use full-spectrum LED shop lights or dedicated T5 fluorescent fixtures. Avoid standard incandescent bulbs, as they generate too much heat and lack the intensity needed for healthy growth.
  2. Fill and Settle Your Trays. Fill modular seed trays or cell packs with a high-quality, pre-moistened seed starting mix. Tap the trays firmly on your table to settle the mix and eliminate large air pockets.
  3. Plant Seeds at Perfect Depth. Place seeds at the depth indicated on the packet, usually two to three times their diameter. Gently cover them with a light dusting of medium and press down firmly to ensure good soil-to-seed contact.
  4. Lock in Humidity for Germination. Cover your trays with a clear plastic dome or plastic wrap to lock in humidity until germination occurs. Remove the humidity cover as soon as the first green loops break the surface.
  5. Position Lights Two Inches High. Hang your lights so they are adjustable, setting the fixture no more than two inches above the top of the seedlings. Raise the lights incrementally as the plants gain height to maintain that two-inch clearance.
  6. Strengthen Stems With Air Flow. Set up a small oscillating fan near the trays to provide gentle airflow across the seedlings. This strengthens the stems and prevents fungal issues caused by stagnant air.