How to Grow Petunias from Seed (Beginner’s Guide)

Petunias are one of the most rewarding flowers to start from seed — reliable, fast and endlessly colorful. Here is what works.

Sowing

Petunia seeds are tiny and need light to germinate. Press them onto the surface of moist seed-starting mix without covering, and keep soil warm at about 70–75°F. Germination takes 7–14 days.

Light & water

Once sprouted, petunias want plenty of light — a grow light or sunny window — and evenly moist (not soggy) soil. Water from below to avoid damping off.

Pinching & planting out

When seedlings have a few true leaves, pinch the tips to encourage a full, trailing shape. Harden them off and move outside after the last frost into full sun. Plant 8–12 inches apart.

Ongoing care

Deadhead spent blooms and feed lightly every couple of weeks through summer for continuous flowers until frost.

USDA note: petunias are grown as warm-season annuals everywhere; they behave as perennials only in zones 9–11.