Growing lettuce and herbs under shelf lights

Lettuce germinates in light, prefers cool temperatures and turns over in 3 to 5 weeks.

Facts from the sources

Light to germinate: NC State lists lettuce as needing light, so leave seeds on the surface or barely covered. See do seeds need light.
Germination temperature: Alabama Extension gives a 35 degree F minimum, 40 to 80 degrees F as the best range, an 85 degree F maximum and 75 degrees F as the single best temperature. A warm shelf or heat mat is not needed.
Timing: Cornell says 3 to 5 weeks from sowing to setting out, and that lettuce grows at 55 to 60 degrees F. NC State says 8 weeks before the last frost. Cornell gives parsley 9 to 10 weeks and basil 6 weeks.
Hours: UConn says greens and herbs can do with about 12 hours of light, below the 14 to 16 hours for most seedlings. See hours per day.

Cool leafy crops do not need warmth under the shelf, so skip the heat mat. See the temperature chart.
Short crops fit shallow shelves, but still need room to raise the light. See hanging height.
Small shelves can use 2-foot bars. See the 24-inch shelf page.

Sources checked 2026-10-14. Pages on this site are researched, not hands-on tested.