What conditions do seeds need indoors?
Written by
Julia Anderson
Reviewed by
Prof. Charles Hartman, Ph.D.By managing perfect indoor conditions, you guarantee consistency with seed germination success in the indoor garden. Unlike an outdoor garden, you can precisely control and manage all environmental factors. Paying attention to containers, soil, temperature, lighting, and moisture is essential. Each factor plays a role in facilitating the seeds' growth potential. Adequate preparation prevents germination failures that occur due to mold or a lack of growth altogether.
Container Setup
- Use trays with drainage holes preventing waterlogging
- Cover with humidity domes maintaining 70-80% humidity initially
- Remove domes immediately after sprouting for airflow
Soil & Temperature
- Sterile seed-starting mix avoids diseases in garden soil
- Maintain 65-90°F (18-32°C) range with heat mats or cool zones
- Monitor with soil thermometer not air temperature readings
Light & Moisture
- Provide 12-16 hours daily from LEDs or fluorescents
- Position lights 2-4 inches (5-10 cm) above seedlings
- Maintain consistent dampness like wrung-out sponge texture
Light quality is just as important, if not more important, than the amount of light. Full-spectrum LEDs actually replicate sunlight best. When using lights, keep them close but adjustable, as you will need to gradually raise the lights as the seedlings grow tall enough to avoid burning them. Rotate your trays once a day to ensure even exposure to the light. If you do not supply adequate light, seedlings will become spindly and go weak.
Moisture management inhibits fungal problems. Wet from beneath with tray irrigation. The soil surface will dry, preventing mold growth. Mist only at soil surfaces that appear dry. Use room temperature water to avoid shock. Consistent dampness without saturation is important.
Temperature needs vary by seed. Group seeds according to temperature needs. Examples include peppers and tomatoes, which are typically found in a warm zone with temperatures ranging from 75°F to 85°F: lettuces and spinach, preferably in cooler zones of 65°F. Therefore, you may use either multiple heat mats or placement altogether. This is very efficient and will greatly increase germination rates.
Begin with easy seeds, like basil. Once you've gotten comfortable with the basics, you can move on to tomatoes or peppers. Use a gardening journal to document conditions, meeting conditions, successes, and things that need adjustment. Your indoor germination skills will improve each time you plant.
Read the full article: How to Germinate Seeds: 7 Foolproof Steps
