Starting Seeds Indoors: A Beginner’s Guide to Growing Strong Seedlings
Starting seeds indoors is one of the best ways to get a head start on the gardening season. By learning how to start seeds indoors properly, you can grow stronger plants, harvest earlier, and enjoy more vegetable and flower varieties.
Why You Want to Start Seeds Indoors
- Get a head start on the season – Harvest earlier by growing strong transplants before outdoor conditions are ready.
- Grow more varieties – Access unique vegetables and flowers not always available as plants.
- Stronger plants at planting time – Well-grown seedlings establish quickly in the garden.
- Better control – Manage light, moisture, and temperature from the beginning.
- Cost effective – A single seed packet produces many plants at a fraction of the cost of buying transplants.
How to Start Seeds Indoors Successfully
- Check the seed packet first – Most packets say “Start indoors 6–8 weeks before last frost.” Count backward from your local last frost date to determine timing.
- Use a quality seed-starting mix – A light, fine-textured mix such as Burpee Eco-Friendly Seed Starting Mix or coir pellets allows roots to develop easily.
- Plant at proper depth – Plant seeds about 2–3 times as deep as their size; very small seeds can be pressed lightly onto the surface. The packet will tell you the exact planting depth and timing.
- Use a reliable tray system – Burpee 16 XL Cell SuperSeed Tray or 36 Cell SuperSeed Tray provide consistent moisture and airflow for healthy root growth.
- Water gently – Keep soil evenly moist but never soggy; avoid letting seedlings sit in standing water.
- Thin seedlings early – Once seedlings have sprouted, thin to one plant per cell by cutting weaker seedlings at soil level instead of pulling to avoid disturbing roots.
- Light is essential – Place seedlings under a grow light or in a sunny window immediately after germination.
- Growing in a window – Place trays in a south- or southwest-facing window, as close to the glass as possible for maximum light.
- Growing under light – Full-spectrum LED grow lights, such as the Fordhook LED Grow Light, provide ideal light for seedling growth.
- Light distance – Keep lights 2–3 inches above seedlings and raise them as the plants grow.
- Light duration – Provide 16 hours of light per day, followed by 8 hours of darkness, for strong, compact growth.
- Temperature – Most seeds germinate best between 65–75°F.
Hardening Off Seedlings
- Size of plants – Wait until seedlings have 6–8 leaves and roots hold soil together before starting hardening off.
- Gradual exposure – Introduce seedlings to outdoor conditions 7–10 days before transplanting.
- Start small – Begin with a few hours in the shade, gradually increasing sunlight exposure daily.
- Bring indoors at night – Protect seedlings from cold or wind until fully acclimated.
- Protection – Shield seedlings from strong winds or extreme temperatures during the process.
- Transplant timing – frost-sensitive plants – Move seedlings outdoors after the last frost date for your area; some crops (like tomatoes, peppers, and basil) cannot tolerate frost, while others (like broccoli or kale) handle light frost.
Extra Tips for Success
- Label everything – Seedlings look alike at first; labeling keeps you organized.
- Air circulation matters – A small fan or ceiling fan strengthens stems and reduces disease risk.
- Rotate trays – Turn trays every few days to prevent seedlings from leaning.
- Don’t overwater – Wet soil invites damping-off disease; soil should be evenly moist, not wet.
Bonus Tip – Burpee Style
- Quick seed-start tip – Keep a simple notebook to track planting dates, germination, and thinning; it helps you time transplants perfectly and avoid guesswork.