Fluorescent Light Duration for Seedlings: 18 Hours On, 6 Off

Optimal Photoperiod for Strong Growth

Run double-tube fluorescent lights 18 hours on, 6 hours off daily. This mimics long spring days and promotes compact, sturdy seedlings.

Don't Forget Soil Temperature

Keep the growing medium at a constant 75°F. Bottom heat from a seedling heat mat makes a dramatic difference in germination speed and root development.