+1 to what Buzz said. Regarding the heating mat - a caution and a consideration. Most (if not all) heating mats are sold without thermostats. If you are going to use a mat, get a thermostat as most get too hot - they will cook your seeds. The thermostats aren't terribly expensive, and are worth it for as many as you are starting. The consideration is that you might not need a mat. I usually start seeds in January/February, and am in N.E. Ohio - snow country. I keep my house pretty cool in the winter, and put my seeds on top of the fridge to germinate - that's enough warmth for them. You're in Long Beach (I used to live not far from you) and it's just the start of September so it's probably still plenty warm outside. You might consider just placing the tray outside in a warm spot. Even if you don't have a warm spot to start them in (such as if you live in an apartment) you still may not need a mat if you have a warm spot in the house - could simply be a sunny window, the top of your own fridge, or even a stereo speaker. Regardless, keep in mind that the mat is only needed for actual germination - once they sprout, remove the mat or the plants may get leggy.