What Are the Germination Periods for Petunias?

Germinating Containers

• To germinate petunia seeds, choose containers to hold your planting medium that can be watered from the bottom and drain well. Ideally, you should be able to place the container in a shallow tray of water and moisten the planting medium from the bottom so that you don't disturb the petunia seeds. If you are reusing containers to germinate your petunias, it is best to wash the pots with a mild detergent and rinse thoroughly before you use them again. The containers should also be sanitized by dipping them in a mixture of 1 part bleach to 9 parts water.

Planting Medium and Moisture

• Use a commercially produced, soil-less pasteurized growing medium to germinate your petunia seeds. Iowa State Extension service recommends using a product like Jiffy Mix or Redi-earth. The containers should be filled to within the top 1/2 inch of the container. Moisten and drain the planting medium before adding the petunia seeds to speed the germination process. While the medium is moist, petunia seeds should be pressed gently into the top of the medium but not covered. To keep the planting medium from drying out and help maintain a consistent moisture level, cover your germinating container with clear plastic wrap or a plastic dome that can be removed when sprouts emerge.

Light

• Petunia seeds require light to germinate. If you bury them in your planting medium, chances are that you will not see many sprouts. Your sprouting containers should be placed in an area where they receive bright, but indirect, sunlight. Light exposure will help your petunias germinate faster. The University of Rhode Island Extension indicates that petunia seeds can germinate in as little as three to four days but it can take up to 12 days, according to the Iowa State University Extension. Once seedlings emerge, they can be placed under a fluorescent light for 12 to 16 hours a day.

Temperature

• A consistent soil temperature will help your petunia seeds germinate quickly. Iowa State University Extension recommends that you place your petunia seeds in an area that is between 75 and 80 degrees Fahrenheit. This temperature range is optimal for petunia seed germination.