When you move to plant peppers outside, your plants will do better once temperatures are staying above 55 degrees F. at night. Before that, they will grow quite slow. Starting pepper plants indoors is best because growing bell peppers require this higher nighttime temperature.rowing bell peppers should be done in the warm season. This usually means you don’t put them outside until sometime near Memorial Day. When thinking about how to grow peppers, remember that they prefer higher temperatures, and when you plant peppers you need to be sure that the chance of frost is long gone.