Seed Treatment
• Cold Stratification Required:
1. Sow seeds on the surface—do not cover.
2. Keep moist at 64–72°F (18–22°C) for 2–4 weeks.
3. Then refrigerate or place outdoors at –4 to +4°C (25–39°F) for 4–6 weeks.
4. Covering the tray with snow during this cooling period is beneficial.
5. After stratification, move to +5 to +12°C (41–54°F) until germination.
If seedlings sprout during cold stratification, gently remove and plant immediately.
Maximum Germination Time
• Up to 90 days or longer with stratification.
Optimum Temperature
• Initial phase: 64–72°F (18–22°C)
• Cooling period: –4 to +4°C (25–39°F)
• Post-stratification: 41–54°F (5–12°C)
Sowing Instructions
• Use acidic, well-draining seed-starting mix.
• Surface-sow: seeds need light to germinate.
• Mist gently and keep consistently moist—not wet.
• Use a humidity dome or clear plastic to retain moisture.
Post-Germination Care
• Grow in bright, indirect light.
• Mist to water—avoid disturbing tiny roots.
• Transplant when seedlings are strong enough to handle.
• Gradually acclimate to outdoor conditions.
Overwintering (If Not Hardy in Your Zone)
• Lift in autumn and pot up.
• Store in a cool, dry place at 45°F (7°C) through winter.
Alternate Method
• Seeds may also be sown at 55–61°F (13–16°C) in late winter, though results may vary.
Note: Rhododendron seeds are slow to germinate and need patience and precise temperature control for success. Best results are often achieved by mimicking natural alpine conditions.