How to Raise Petunias From Seeds

Growing petunias from seeds provides you with more varieties from which to choose.

Growing petunias from seeds provides you with a larger selection of petunia varieties from which you can choose. It also allows you to grow more plants for less money. It does, however, take up to three months before your petunias will be large enough to plant outside. Many novice gardeners shy away from starting petunias from seed due to the amount of time that it takes and the challenge of working with tiny petunia seeds.

Things You'll Need

• Planting medium/soil
• Containers
• Water bottle
• Plastic wrap
• Flats or small pots
• Fluorescent light with timer (optional)
• Liquid fertilizer

Instructions

1. Fill a container with clean potting soil or milled sphagnum moss. Spread petunia seeds on top of the planting medium, pressing the seeds lightly into the soil. Fill a spray bottle with water and apply a fine mist to the petunia seeds.

2. Cover the container with plastic and place in a warm location. According to the University of Minnesota, the room should be between 70 and 85 degrees Fahrenheit. The container should be in a bright spot that does not receive direct sunlight. The seeds should take approximately seven to 10 days to begin to sprout.

3. Remove the plastic covering once the seeds have sprouted. Relocate the container in a cooler location that averages 65 degrees Fahrenheit during the day and between 55 and 65 degrees Fahrenheit during the night. Allow the soil to dry out slightly between waterings; however, it is crucial that you water your young plants regularly during the next two to three weeks.

4. Transplant seedlings into flats or individual peat pots once they have two to three leaves. Fertilize seedlings with diluted liquid fertilizer once every two weeks for the next six to eight weeks until plants are ready to be planted outdoors.

5. Ready your young petunia plants for planting outdoors. Approximately one week prior to planting outside, place petunias outside during warm, sunny days. Bring plants indoors at night.

6. Plant petunias outdoors once the danger of frost is over and the soil is 60 degrees Fahrenheit or warmer. Space plants between six and 18 inches apart, depending on the variety that you are planting.

Tips & Warnings

• Place your petunias beneath a fluorescent light for 16 to 18 hours daily for optimal results. You can begin doing this as soon as you sow the seeds; always maintain a distance of four to six inches between the seeds/plants and the light fixture. Continue exposing seedlings to light until you are ready to plant outdoors.

• Grandiflora and multiflora petunias should be placed 12 inches apart. Space milliflora varieties between four and six inches apart. Plant spreading varieties 18 inches apart.

• Deadhead dying petunias throughout the growing season to encourage extended blooming.

• Avoid soil temperatures cooler than 70 degrees Fahrenheit during seed germination to minimize the risk of your seedlings contracting damping-off disease.

References

• University of Minnesota Extension: Growing Petunias
• University of Rhode Island Landscape Horticulture Program: Growing Petunias