Grow lights for tomato seedlings

Start about 6 weeks before the last frost, germinate warm, and keep lights close.

Facts from the sources

Timing: NC State says 6 weeks before the last frost. Cornell says 6 to 8 weeks from sowing to setting out. Use the frost-date calculator.
Germination temperature: Alabama Extension gives a 50 degree F minimum, 70 to 95 degrees F as the best range, and 85 degrees F as the single best temperature. Cornell says to germinate at 75 degrees F and grow at 65 degrees F.
Light to germinate: NC State lists tomato as germinating in either light or dark.
Light after sprouting: hours and distance depend on the fixture. See hours per day and hanging height. Oklahoma State says seedlings do best under cool white light.
Lights per shelf: Saskatchewan shows two 4-foot fixtures over a 24 x 48 inch shelf, and says fruiting plants grown to maturity such as tomatoes may want up to four. See the 4-foot shelf page.

Tall, thin seedlings point to weak light. Utah State says to add light close to the plants and lower the temperature. See leggy seedlings.
Utah State lists tomatoes among warm-season plants to keep above 45 to 50 degrees F when hardening off. See hardening off.

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