When to Use Grow Lights for Seedlings？

Is a grow light necessary for seedlings? The short answer is: it depends!

Seedlings need 12–16 hours of bright, consistent light daily to develop strong stems and healthy leaves. If your space lacks south-facing windows (or if you’re starting seeds in winter, when daylight is short and weak), seedlings will stretch toward dim light, becoming “leggy” (thin, fragile stems) and more prone to disease. Grow lights fix this gap: they deliver targeted light that mimics sunlight, ensuring seedlings get the intensity and duration they need to thrive—no matter the season or space.

What Plants Actually Need Grow Lights for Seedlings, and When?

  • Leafy greens (lettuce, kale): Start using lights the day seeds germinate (usually 3–7 days after sowing). They need 12–14 hours of light daily to avoid legginess.
  • Tomatoes, peppers, and eggplants: These warm-weather veggies are slow to mature, so gardeners often start them 6–8 weeks before the last frost. Since this is typically in late winter/early spring (low light), use grow lights immediately post-germination for 14–16 hours daily.
  • Herbs (basil, cilantro): Delicate and quick to stretch, they need lights within 2 days of sprouting (12–14 hours daily).
  • Root crops (carrots, beets): Less critical if you have bright windows, but grow lights still help produce stockier seedlings (use 10–12 hours daily if light is limited).

The key rule: if seedlings are leaning, their leaves are pale, or stems are thin within 1–2 weeks of sprouting, it’s time to add a grow light.

Check our 18W Tubular LED Grow Lights for Seedlings and Cloning!

LED Grow Lights for Seedlings

Which Spectrum Suits Seedlings?