Here’s a , covering seed starting, transplanting, and regional timing for maximum blooms. 1. Key Principle: Petunias Hate Frost Petunias are tender perennials (grown as annuals in most climates). 👉 Never plant outdoors until after the last spring frost. Soil temperature should be at least 60°F (15°C) — ideally 65°F (18°C). 2. When to Start Petunia Seeds Indoors | Growing Method | Timing (before last frost) | |----------------|----------------------------| | Standard seeds | 10–12 weeks | | Pelleted seeds | 8–10 weeks (easier to handle) |
If your last frost is May 1, start seeds Feb 15–Mar 1 . ⚠️ Petunia seeds are tiny and need light to germinate — press into soil, don’t cover. 3. When to Plant Transplants / Seedlings Outdoors | Climate Zone | Approximate Outdoor Planting Time | |--------------|------------------------------------| | Zones 3–4 | Late May to early June | | Zones 5–6 | Mid-May | | Zones 7–8 | Mid-to-late April | | Zones 9–10 | March (or fall for winter color) | when to grow petunias