Contact the local extension to determine the average date of the last spring frost. Begin seed propagation 12 weeks before the final frost.
Choose containers for the seeds. Use any material that is waterproof and holds its shape: egg crates, plastic cell packs, yogurt containers, old cans, paper cups, etc.
Soak containers for 20 to 30 minutes in a sanitizing solution made from ¾ C. bleach and 1 gal. warm water. Rinse them well and then set them in the sunlight to dry.
Punch two to four holes in the bottom of each container with a screwdriver or ice pick.
Scoop commercial potting soil into the containers and fill them to within 1 inch of the rim.
Sprinkle water over the top of the soil and press down lightly to compress the planting media.
Fold an index card in half, lengthwise. Pour some seeds into the groove, and then use a toothpick to transfer three or four seeds from the card onto the soil.
Scatter loose potting soil over the top of the seeds to bury them.
Mist the soil lightly with lukewarm water, then cover the containers with sheets of plastic cling film, and set them in a warm, well-lit location.
Check the seeds at least once a day. Add water as often as needed to keep the soil moist.
Remove the plastic cling film when the first leaves appear; when the sprouts are 3 to 4 inches tall, thin the seedlings down to one plant per container.
Transplant the seedlings into the garden in the early summer, leaving 12 inches of space between each plant.