Start seeds indoors for the best variety. You'll find only a selection of plant choices at garden centers and nurseries. And it's an inexpensive option to grow a range of plant types. Start many vegetable seeds up to 14 weeks before planting and some flower seeds up to 12 weeks for a summer garden. Give your seeds the best start by providing them with the best care.
Read seed packets to determine when to start. Start seeds from four to 14 weeks before planting outdoors.
Fill a bucket or sink with bleach. Soak any previously used cell flats in the bleach for 30 minutes to sterilize. After 30 minutes rinse the cell flats with tap water and dry with a clean towel.
Set the cell flats in a tray. Fill the cell flats with the seed-starting mix. Water the cell flats with a light spray until moist.
Sow one to two seeds in each cell. Seed packets advise on planting depth; typically, plant seeds four times as deep as their width. Press the seed into the soil and place a layer of soil back over the seed.
Cover seeds with a layer of fine vermiculite, available at most garden centers, if they require light to germinate. Seeds that require light for germination include lettuce, impatiens and petunias. If seeds require darkness for germination, place cell packs in a dark plastic bag until they sprout. Seeds that require dark germination include verbena and annual phlox. Consult your seed packet for specific light needs during germination.
Place cell flats in an area free of hot or cold drafts, away from heat registers. Maintain the air temperature above 60 degrees F.
Hang a fluorescent light over the cell flats. Suspend the lights from a chain. Move the lights up as the seedlings emerge and grow. Keep lights 2 inches from the top of seedlings. Only turn on the lights for 12 to 16 hours per day. Give the plants a period of dark for proper development.
Spray the soil in the cell flats with a light mist of water from a spray bottle whenever the soil appears dry. Stick just the tip of your finger in the soil to test dryness. If you feel moisture, skip watering.