The calendar date depends on your climate. I use mine to start tomatoes about 4 weeks before my average last frost date.Go into the "Goodies" section and pick the Garden Planting Calendar. Enter your zip code for the average last frost. The four weeks give me a good headstart and the tomatoes are just growing out the top by the time all danger of frost is past. I can take the water walls off the plants and the tomatoes really take off.
David R
