Sowing Seeds Outdoors

• Zinnia plants are tolerant of almost any kind of soil type except wet or poorly drained, but prefer humusy, uniformly moist soil. Select a site in full sun and sow seeds directly in the ground. In hot Southern regions, select a site with some afternoon shade to keep the plants from burning. Plant seeds in spring, after the last frost date in your area, when nighttime temperatures remain at least 50 degrees Fahrenheit. To extend the flower show, put out more seeds at two- to three-week intervals until June. Zinnia seeds germinate well, so don't sow the seeds too close together in the garden. Make furrows in the soil and fill it with vermiculite. Sow the seeds on the vermiculite and cover lightly with more vermiculite. Water using a fine mist.
  
  

Starting Seeds Indoors

• Zinnia seeds may be germinated indoors four to six weeks before the last frost of spring. If you use peat pots that will go directly into the ground later, place seeds singly in 2- to 3-inch pots and cover each seed loosely with a little planting medium. In flats, use a planting medium with a pH of 5.8 to 6.2. The distance between seeds may vary between different types of zinnias, so follow the seed package directions for seed spacing. Cover the seeds lightly with soil or vermiculite and mist thoroughly. Seeds germinate best in temperatures around 70 degrees Fahrenheit. Transplant the seedlings to the garden as soon as temperatures stay above freezing.
  
  

Seed Tapes

• Although more expensive than loose seeds in packets, seed tapes are exquisitely simple to use. Zinnia seed tapes contain seeds suspended in a water-soluble medium that melts away to let the seeds germinate. Seed tapes eliminate overcrowding of seedlings and can be cut to fit any length desired. With tapes, you can arrange zinnias ramrod straight along sidewalks, driveways and paths.
  
  

Harvesting Seeds

• When zinnia blooms fade and dry out, cut them off -- called deadheading -- to encourage further flowering. Remove seeds from the spent flowers and store them in an airtight container in the refrigerator. Put a little powdered milk in the container with the seeds to absorb excess moisture. The seeds will almost certainly produce plants and flowers slightly different from the parent plant.