Flower / Warm season
Grandiflora Petunia
Hanging baskets, patio containers, and warm-season annual borders.
Grown for large colorful blooms, not edible harvest.
Seed spacing and maturity
- Days to maturity
- 85
- Germination temperature
- 70-80F
- Seed depth
- 0.125 inches
- Spacing
- 12 inches
- Row spacing
- 18 inches
- Start method
- Start indoors
Frost-date timing
- Indoor start
- 10 weeks before last frost
- Transplant
- 14 days after last frost
Action plan
- Can I plant this now?
- Use your local last-frost, first-frost, and soil-temperature checks before treating this crop as plantable today.
- Start indoors or direct sow?
- Start indoors, harden off, then transplant into the final bed when local timing is safe.
- How much space?
- 12 inches in-row spacing, 18 inches between rows, and 0.125 inch seed depth.
- Best companions?
- Use this as part of a diverse flowering or herb planting, and treat companion claims as site-specific rather than guaranteed pest control.
- Common failure modes?
- Seed is tiny and slow; do not bury deeply. Moderate water with good drainage in containers and beds. Light, fertile, well-drained soil or container mix.
Growing profile
- Sun
- Full sun
- Water
- Moderate water with good drainage in containers and beds.
- Soil
- Light, fertile, well-drained soil or container mix.
- Watch
- Seed is tiny and slow; do not bury deeply.
- annual
- containers
- transplant
- warm-season
Browse context
- Flower Catalog Category collection
- Nightshade Family Rotation and family context
- Warm Season Seeds Season collection
- Start Indoors Seeds Start-method collection
- Container-Friendly Seeds Practical trait collection
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Source: UMN starting seeds indoors