About Petunias
Petunias are among the most popular and versatile summer annuals, producing trumpet-shaped blooms in a huge range of colors — from soft pastels to vivid purples, pinks, reds, and striking bicolors. They excel in containers, hanging baskets, window boxes, and garden borders, blooming continuously from late spring through frost. Spreading varieties cascade beautifully, while grandiflora types produce impressively large individual blooms.
Starting from Seed
Start petunia seeds indoors 10 weeks before your last frost date. The seeds are very fine. Sow on the surface of moist seed-starting mix — do not cover, as petunia seeds require light for germination. Maintain planting media temperature at 72-76°F using a heat mat. Germination takes 7 to 10 days. After germination, reduce temperature to 60-65°F and provide 12 to 16 hours of light daily from grow lights positioned 4 to 6 inches above seedlings. Petunia seedlings grow slowly at first but accelerate after developing several true leaves.
Planting Out
Transplant after all frost danger has passed into full sun — petunias need at least 6 hours of direct sunlight for best flowering, and more sun equals more blooms. Space 10 to 12 inches apart in well-drained, fertile soil. Petunias perform exceptionally in containers — use a quality potting mix and ensure containers have drainage holes. Hanging baskets and window boxes are where spreading petunias really shine.
Watering & Feeding
Water when the top inch of soil is dry. Container petunias need daily watering in hot weather — they're heavy drinkers when in full sun. Petunias are also heavy feeders: apply a balanced liquid fertilizer every 1 to 2 weeks throughout the growing season. Without regular feeding, flowering declines noticeably by midsummer.
Ongoing Care
Deadhead spent blooms to encourage more flowers. By midsummer, petunias can become leggy and sparse. When this happens, cut plants back by about half — they'll regrow vigorously and produce a fresh flush of blooms within 2 weeks. This midsummer rejuvenation trim is the single best technique for keeping petunias looking great all season. Petunias pair beautifully with French marigolds and annual phlox in borders, or with trailing nasturtiums in mixed containers.