When to Start Begonia Seeds Indoors for Spring Planting

Begonia seeds are dust-fine and slow—they need an early start.

Timing

• Sow 12 weeks before last frost (January–February for April planting).
• Press onto surface of moist sterile mix—do not cover (light required).
• Keep at 75–80°F; high humidity (plastic dome).
• Germination in 2–3 weeks.

Transplanting Out

• Wait until nights consistently >50°F.
• Harden off 7–10 days.
• Plant in shade/part shade, rich moist soil.

Key Tips

• Use fine mist or bottom water—seeds wash away easily.
• Fertilize weakly after true leaves appear.
• Tuberous begonias: start tubers indoors same timeline.

Early start = summer-long blooms. Don't rush outdoors—cold kills them fast.