Iowa State University
Extension and Outreach Horticulturist
Many gardeners like to get a head start on the gardening season by starting flower and vegetable seedlings indoors. Successfully growing seedlings indoors requires high quality seeds, a germination medium, containers, lights and other supplies, note horticulture specialists with Iowa State University Extension and Outreach. To have additional questions answered, contact the Hortline at 515-294-3108 or hortline @iastate.edu.
How do I get started?
The first step is purchasing seeds, and flower and vegetable seeds can be purchased at local garden centers and other retailers. They are also available from numerous mail-order companies.
Mail-order/internet sources include (but are not limited to):
• Park Seed, One Parkton Ave., Greenwood, SC 29647 (www.parkseed.com)
• W. Atlee Burpee, 300 Park Ave., Warminster, PA 18974 (www.burpee.com)
• Stokes Seeds, P.O. Box 548, Buffalo, NY 14240 (www.stokeseeds.com)
• Harris Seeds, P.O. Box 24966, Rochester, NY 14624 (www.harrisseeds.com)
• Johnny’s Selected Seeds, 955 Benton Ave., Winslow, ME 04901 (www.johnnyseeds.com)
• Seed Savers Exchange, 3094 North Winn Road, Decorah, IA 52101 (www.seedsavers.org)
What should I consider?
When germinating seeds, the medium should be lightweight, porous and free of pathogens. Excellent seed-starting media are commercially prepared soilless mixes, like Jiffy Mix.
There are plenty of container options that can be used to start transplants. Gardeners can purchase flats, trays, pots, compressed peat or coir pellets and other products. Previously used flats, trays and pots should be cleaned and disinfected before use. Wash previously used containers in soapy water, then disinfect them in a solution of one-part chlorine bleach and nine-parts water. Cut-off milk cartons, plastic jugs, paper cups, plastic food boxes and other containers can also be used to start seeds. Holes should be punched in the bottom of milk cartons, jugs, paper cups and similar containers to allow for drainage.
Most flower and vegetable seeds germinate best when the temperature of the germination medium is 70-75 degrees Fahrenheit. Placing containers in a warm location in the house, such as near a heat register, usually works fine. In cool environments, electric heat mats can be used to ensure medium-warm temperatures.
While seedlings can be grown in a sunny window, they often become tall and spindly because of insufficient light. For best results, grow seedlings under fluorescent lights. Expensive “grow lights” are not necessary. A standard fluorescent fixture with two 32- or 40-watt tubes works fine. The fluorescent lights should be positioned no more than 4-6 inches above the seedlings. Keep the lights on for 12-16 hours each day.
For more information on starting seedlings at home, refer to the ISU Extension and Outreach publication "Starting Garden Transplants at Home."