13 Secrets to Starting Seeds Indoors
Seed Starting 101
Starting seeds indoors gives you a jump on the season and allows you to try more varieties than will be available locally.
Schedule Your Seeds
Good timing is critical for starting seeds indoors. To ensure you begin starting seeds at the proper time, determine the last frost date in your area (contact your Cooperative Extension Office for this date). Then read each seed packet to learn how many weeks before the last frost date the seeds should be sown and when they should be planted outside. Using a calendar, calculate when you'll need to sow seeds so the plants are ready for transplanting outdoors. The worksheet below will help you detail each vegetable, its plant date, and when to transfer it to your garden.
Prep Your Pots
Choose containers based on your needs and preferences. Thoroughly clean terra-cotta or plastic pots before reusing them for seed starting. Use large clay or plastic pots with drainage holes, also known as community pots, for starting a group of seedlings. Peat pots, cell packs, and pellets can be directly planted outdoors, so they are ideal for plants with delicate roots. For large sowings, use plastic cell packs for convenience.
Use a Soilless Mix
Use a sterile soilless mix that is about one part milled peat moss and one part vermiculite with some perlite. Most commercial seed-starting mixes also have enough fertilizer for about two weeks. Never use a mix containing topsoil or compost.
Gather Trays and Plastic Covers
Use plant trays under pots for bottom watering. Clear plastic wrap can be used to cover germinating seeds.
Add Water to Soilless Mix
In a large bucket or tub, gradually add tepid water to sterile soilless mix until it is evenly moist but not wet.
Cover the drainage holes of clay or plastic pots with a small piece of newspaper, and fill containers to the top with moistened mix. Gently tamp down mix so surface is firm and level, about 1/2 inch from the top.
Make Seed Holes
Using a dibber or pencil, make holes in mix, about twice as deep as the seed is wide, and sow seeds at the depth and distance recommended on the seed packet. Cover with more mix unless otherwise specified. Seeds that require light to germinate can be sprinkled on the soil surface.
Label pots with the type of seed and the date sown. Bottom-water containers by setting them in trays filled with an inch of tepid water. Remove pots as soon as soil surface feels moist.
Cover containers with clear plastic before placing them 2 to 3 inches below grow lights. A simple two-tube fluorescent shop light is ideal. For seeds that require darkness to germinate, use an opaque cover, and set them in a warm spot such as the top of a refrigerator.
Keep the seed-starting mix moist until germination is complete and the emergence of new seedlings slows markedly or stops. Remove covers, and if you haven't already, place seedlings under grow lights, leaving lights on about 14 to 16 hours per day. The light should be on chains so that it can always be positioned just one to two inches above the tallest seedling. Continue to bottom-water, removing pots promptly once they've been thoroughly moistened.
As soon as seedlings produce their first true leaves, begin watering with a balanced fertilizer or fish emulsion diluted to one-quarter strength. Prick out seedlings planted in community pots, and transplant them to individual pots or cell packs filled with moist soilless mix. Handle seedlings by their leaves rather than by their delicate stems.
Water and Raise Lights Higher
When soilless mix dries, water transplanted seedlings using a water breaker or mister that produces a gentle spray. As seedlings grow, raise grow lights, keeping them 2 to 4 inches above plants.
Transplant and Acclimate
If the seedlings are outgrowing their pots, transplant them to larger vessels as they grow. Before planting outdoors, gradually harden off seedlings: Two weeks before transplanting, place seedlings outdoors for a few hours at a time in a sheltered location, gradually increasing their time outside until they are acclimated.