Start seeds indoors approximately eight weeks before the last frost is expected. Bell pepper plants do not tolerate soil temperatures below 65 degrees Fahrenheit. Starting bell peppers indoors extends the growing season because you don't have to wait for temperatures outside to heat up.
Use a container that is at least 5 inches deep. Seed germinating containers made out of peat or other biodegradable material are ideal because when the bell pepper plants are ready to transplant outdoors, you can avoid root disruption by planting the entire pot. Whichever type of container you opt for, ensure it drains sufficiently.
Fill the container with a lightweight, potting mix. Look for products that contain sphagnum peat moss, peat humus, perlite, dolomitic lime or gypsum. Tamp the soil into the container, but not too tightly.
Water the potting mix thoroughly, but don't saturate it. Watering the potting mix before planting the seeds prevents the seeds from floating to the surface, which usually happens when newly planted seeds are watered overhead.
Press the bell pepper seeds into the potting mix about 1/4 inch deep. Cover the tops with a thin layer of pulverized sphagnum moss to help prevent damping off, which is a fungal disease that affects seedlings. It can kill seedlings before they even break through the surface or when the seedling is just an inch or two tall.
Keep the seeded containers warm. Bell peppers won't germinate in soil below 65 degrees, but 80 to 90 degrees is best. Keep the air in the growing environment between 70 and 75 degrees. Place the container on top of a refrigerator to help keep the containers warm.
Set the container inside a tray and add water to the tray to irrigate the seeds. Keep the potting mix constantly moist, but not waterlogged. Once the soil is moist enough, dump out the rest of the water in the tray.
Wait up to 10 to 14 days for bell pepper germination to happen. When the seedlings are six to eight weeks old, begin hardening them off by placing them outside in a partially shaded, wind-protected area. Start with only an hour or two at first, and gradually expose them more over the next week or two.