How To Start Seeds Indoors Under Lights (COMPLETE GUIDE)

Quick Overview

To successfully start seeds indoors under lights, use a fine, uniform, moist (but not soaking wet) seed starting mix, plant seeds to a depth of twice their width, and keep the grow light very close (about 2-4 inches) to the seedlings, adjusting it upward as they grow to prevent legginess, while supplementing with liquid organic fertilizer once true leaves appear.

Key Points: Seed starting requires a fine, uniform growing medium without large particles or bark to ensure good root contact and prevent air pockets. Seeds should generally be planted to a depth of twice their width, though some small seeds like dill may only need surface sowing. For large seeds like squash or beans, placing the pointed end up ensures the root grows down, while small seeds like dill should be barely covered. A grow light should be kept very close—around 2-4 inches—to the seedlings, adjusting the light height upward as the plants grow to prevent etiolation (legginess). Seedlings should receive 12 to 16 hours of light daily, which can be managed using a timer. Once true leaves appear (usually 1-2 weeks after germination), begin fertilizing once per week with a diluted liquid organic fertilizer, such as FoxFarm Grow Big. Hardening off seedlings by gradually exposing them to outdoor conditions (wind and direct sunlight) over a week or two before transplanting is crucial to prevent transplant shock.

Context: The video provides a complete guide on starting seeds indoors using artificial grow lights, contrasting the initial germination phase with the subsequent growth phase requiring light and nutrients. The presenter demonstrates the process using various seed types—including tomatoes, onions, beans, squash, and herbs like cilantro and dill—in multi-cell trays, emphasizing the importance of proper soil preparation, planting depth, light management, watering techniques, and eventual hardening off before transplanting.

Detailed Analysis

The complete guide for starting seeds indoors under lights covers material selection, planting techniques, and post-germination care. Essential materials include seeds, planting trays (like the 1020 bottom tray with 6-cell or 4-cell inserts), a fine seed-starting mix, a grow light, and a heat mat (optional but recommended). The growing medium must be fine and uniform, with no large chunks of bark or rock, to allow young roots to adhere easily. Planting depth should be twice the seed's width; for large seeds like squash, plant the pointed side up. For small seeds like dill, surface sowing is appropriate. Once planted, bottom-watering is recommended to wick moisture up through the soil, ensuring even moisture without disturbing the seeds. Seed germination rates vary by plant; tomatoes take about 7-9 days at 75°F, while dill can take 20-25 days. Once seedlings emerge (showing their seed leaves), the grow light is critical and must be kept very close (2-4 inches) to prevent etiolation (stretching). The light should run for 12-16 hours daily, preferably on a timer. Once true leaves appear (usually 1-2 weeks post-germination), begin feeding with a diluted liquid organic fertilizer, such as FoxFarm Grow Big (half a teaspoon per gallon, once per week). Finally, before transplanting seedlings outdoors, they must undergo hardening off by gradually increasing their exposure to wind and direct sunlight over 7-10 days to prevent transplant shock.