Petunias come in many varieties, single blooms and double blooms, with ruffled petals or plain. Collecting and saving seeds from petunias allows you to grow your favorite varieties each year without the expense of purchasing new seeds or transplants. Petunias produce small seed pods under the petals once the flowers begin to fade. Timing is crucial when collecting petunia seeds, as they are so small they are lost once the seed pods split open.
Check the petunia flowers daily for signs of wilting or drooping petals. Be prepared to collect the seeds as soon as the blooms begin to fade.
Place a small cloth bag over the top of the flower head once the petals begin withering. Use a small cotton bag or the tulle bags that are sold for party favors. Secure the bag to the flower stem with a paper clip.
Check the seed pod daily once the cloth bag is on it. Cut the flower stem off once the seed pod begins to split and release seeds.
Remove the bag, taking care not to spill any seeds. Hold the pod over the bag and finish splitting it open, shaking out the remaining seeds.
Mark an envelope with the petunia variety and year harvested. Place the seeds inside; then store the envelope in a cool, dry place until it is time to replant the seeds.