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Purchase high-quality seeds packed for the current year. Before using them, test old seeds, and always store seeds correctly for later use.
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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 are naturally sterile, and because they can be directly planted outdoors, they are ideal for plants with delicate roots. For large sowings, use plastic cell packs for convenience.
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Use a sterile soilless mix that's about one part milled peat moss to one part vermiculite with some perlite. Most commercial seed-starting mixes also have enough fertilizer for about 2 weeks. Never use a mix containing topsoil or compost.
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Planting Trays and Covers
Use plant trays under pots for bottom watering, and top seeds with a clear cover. Clear plastic wrap can also be used to cover germinating seeds.
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Always label seeds with the variety and date sown.
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Choose full-spectrum fluorescent lights that can be positioned directly above seeds and raised as seedlings grow. Grow lights not only provide the light required for healthy development, but they also warm the soil, speeding germination.
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Before starting seeds indoors, find out the last frost date in your area. Read the seed packets to learn how many weeks before this date they should be started and when the seeds should be planted outdoors. Calculate your sowing date accordingly.
Did you know that poppy seeds can be scattered directly on the winter ground -- even on patches of snow? The seeds need weeks of cold to germinate, and plants will begin to emerge in spring.
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In a large bucket or tub, gradually add tepid water to sterile soilless mix until it is evenly moist but not wet.
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Cover the drainage holes of clay or plastic pots with a small piece of newspaper, and fill containers to the top with moistened mix. Tamp down mix so surface is firm and level, about 1/2 inch from the top.
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Using a dibble 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.
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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.
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Cover containers with clear plastic before placing them 2 to 3 inches below grow lights. 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
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Check Containers Daily
Once you've sown seeds indoors, check containers daily for new shoots. 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. Continue to bottom-water.
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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. Lift seedlings by their leaves rather than by their delicate stems.
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Raise Grow Lights
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.
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Transplant if Necessary
If necessary, transplant seedling to a larger pot as it grows. Before planting outdoors, gradually harden off seedlings: Two weeks before transplanting, place seedlings outdoors for a few hours at a time, gradually increasing their time outside until they are acclimated.
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Martha and her head gardener Ryan McCallister get ready for spring in the Bedford Farm greenhouse -- and show you all you need to know about indoor seed starting.