Growing Tips: Petunia

Quick Reference:

Annual, a plant that completes it’s life cycle in one season. Germinates in 7 to 12 days with an optimum soil temperature of 72 degrees F. Seed needs light to germinate. DO NOT cover seed. Space seed ½ to ¾ inch apart on the soil surface. Space plants 8 to 12 inches apart in the garden. The soil surface MUST be kept moist at all times until seedlings emerge. Plant height: 10 to 15 inches.

When and where to plant:

Petunias grow slowly in cool weather and in Alaska should be started indoors 10-12 weeks before last frost to assure bloom over a long season. Fill a container that has drainage holes with sterilized potting soil, sprinkle the very fine seed on soil surface., DO NOT cover with soil, the seed requires light to germinate. Water well for good seed-soil contact. Cover container with clear plastic and keep warm and moist. Remove the plastic as soon as the seedlings start to sprout. When seedlings show their first green leaves water with a half strength solution of liquid plant food. When the seedlings reach their 3-4 leaf stage, transplant to individual plastic pots, grow in a warm, sunny area and water with a liquid solution of plant food every two weeks and until the garden is ready. Petunias transplant easily. Plant outdoors in a sunny location, in rich, light, sandy, well drained soil. Cultivate the soil, enrich it with plant food and organic matter and transplant seedlings to the garden after the danger of frost is past. Seeds that are started directly in the garden will bloom in very late summer.


Almost no other annual succeeds so easily. Once planted in the garden keep soil moist and feed with plant food monthly. For denser plants and more flowers, pinch or shear plants when 6"/15 cm. tall, the more the plants are sheared the more they bloom.