Starting Seeds Indoors Successfully

Place seedlings under fluorescent shop lights or LED grow lights positioned 2-4 inches above the foliage for 14-16 hours per day. A sunny south-facing window can supplement but rarely provides enough light alone, especially during cloudy spells or short winter days.

Gradually acclimate indoor-grown seedlings to outdoor conditions over 7 to 14 days before planting them in the garden. Start by placing them in a shaded, sheltered spot for two to three hours on the first day, then increase sun exposure and duration each day until they spend a full day and night…

Start seeds in a purchased, sterile seed-starting mix using clean or new containers. Never use garden soil, which is too dense, may contain weed seeds, and often harbors pathogens. If reusing pots, scrub them with soap and soak in a 10% bleach solution before rinsing thoroughly.

Keep the seed starting mix consistently moist but never waterlogged. Water from the bottom by setting containers in a shallow tray of water and letting the mix wick moisture upward. Use a humidity dome over the tray until seeds germinate, then remove it promptly to allow air circulation.

Keep soil temperature at 70-80°F (21-27°C) during germination using a seedling heat mat placed under the tray. Once seedlings emerge, reduce the ambient temperature to 65-70°F (18-21°C) for sturdy growth. Remove the heat mat after most seeds have sprouted.

Plant each seed at the depth specified on its packet. The general rule is to sow a seed two to three times as deep as its width. Very fine seeds like lettuce and petunias are pressed onto the surface and left uncovered because they need light to germinate.

Set a small fan on low speed near your seedling trays for a few hours each day. Direct the airflow near the seedlings rather than blasting them head-on. Remove humidity domes as soon as seeds have germinated to let fresh air reach the soil surface.