Petunias are dependable annuals, perfect in containers, hanging baskets or in a flower bed. The range of colors is almost endless, from white to pastel pink and yellow to bright purple and hot pink. Although the surefire way to get started with petunias is to purchase bedding plants, if you're adventurous, you can collect seeds from existing petunias, and plant them the following year. Keep in mind that only a small percentage of the seeds will be viable, and that there is no guarantee the color will be the same as the original plant.
Choose a few of your healthiest petunia plants, and allow several petunia blooms to die on the plant. When they are completely dead, cut the blooms from the plant with a pair of garden shears. Save the seed pod, or calyx, on each dead petunia. It will look like a small, plump pod at the base of the bloom.
Toss the seed pods in a paper sack, and put the sack in a dry, well-ventilated place. Let the seed pods dry for several days, or until they are completely dry. If you want, you can leave them in the paper sack until spring. If you're saving seeds from plants of different colors, put each color in a separate sack and label the sack. A paper lunch bag works well for small amounts.
Remove the seed pods from the bag, and working carefully, open the calyx and remove the small, round seeds. Put the petunia seeds in a resealable plastic bag or other sealed container, and store them in a dark, cool place until spring planting time.