Petunia plants are a popular annual flower as they are each to grow, produce flowers quickly, and offer long flower periods. Many varieties of petunia will grow from the seedling stage to a flowering plant in approximately 8 weeks. Petunias can be propagated easily through seed starting by collecting seed pods from mature plants or purchasing seed varieties at gardening stores.
Starting Petunia Seeds
Collect the seed pods that form below the flower after they have turned brown and dry. Place the pods on newspaper and let dry in a cool location. Shake the pods to release the dried seeds. Place the seeds in an envelope that is labeled with the collection date for future planting.
Start seeds indoors 10 to 12 weeks prior to the date you want to plant outdoors. Fill a seed starting tray with damp seed starting soil. Carefully spread seeds on top of the soil.
Water the seeds by gently spraying with a misting bottle to wash them into the top layer of starting medium. Continue to water the tray so the soil is always moist.
Cover the tray with a clear plastic cover or clear plastic wrap. Place the seed tray on a sunny or lighted location that has a temperature between 70 to 85 degrees F. Do not set the seeds in direct sunlight until they have sprouted, approximately 7 to 10 days after seeding.
Remove the cover from the tray once the seedlings sprout. Move the tray to a bright or lighted area that has a temperature of approximately 65 degrees F.
Place the petunia seed trays indoors 4 to 6 inches under fluorescent lighting until they are ready for outdoor planting. Set a timer so there is light available 16 to 18 hours per day. Increase the light height as the plants grow.
Transplant the seedlings to pots or six-pack containers once they produce three true leaves.
Fertilize the plants with a diluted liquid fertilizer every 2 weeks after they have been transplanted.
Harden the plants several weeks prior to planting outdoors by placing them in an outdoor sunny location on warm days. Bring the plants in at night during this time to prevent cold damage.