For optimal germination rates, initiate seed propagation indoors under controlled conditions—unless the species exhibits a high sensitivity to root disturbance. This approach allows precise regulation of temperature, humidity, and light, improving germination consistency and seedling viability. Do not skip any recommended seed treatments, as they are essential for uniform and successful germination.
Seed Treatment (Before Sowing)
• Cold Stratification Required:
1. Moisten a paper towel or small amount of vermiculite/perlite (damp, not soaked).
2. Place seeds inside and seal in a labeled plastic bag.
3. Refrigerate at 4°C–5°C (39°F–41°F) for 3–4 weeks.
4. Check weekly: If seedlings sprout in the fridge, remove & plant immediately.
Optional: GA₃ (Gibberellic Acid)
Can be used to stimulate germination after stratification, but use with caution—too high a dose can damage seeds. Recommended only for experienced growers.
Best Time to Sow
• Indoors: 6–8 weeks before last frost
• Outdoors: Late spring or early autumn (in mild climates), after stratification
Germination Conditions
• Optimum Temp: 15–20°C (59–68°F)
• Light Requirements: Use grow lights 12 to 16 hours per day
• Germination Time: 14 to 45 days after stratification
Sowing Instructions
• Surface sow — do not cover with soil
• Press gently into the surface of moist, well-draining seed-starting mix
• Mist to keep moist, not wet
Humidity: Use a humidity dome or clear cover to maintain consistent moisture during germination. Open the dome BRIEFLY once per day to allow fresh air in and reduce mold risk. Remove the dome entirely once seedlings emerge.
Post-Germination Care
• Remove cover once seedlings appear
• Transplant when 2–3 sets of true leaves form
• Harden off seedlings gradually before planting outdoors
• Space 30–40 cm (12–16") apart
Growing Tips
• Prefers full sun to partial shade
• Soil: Moist, well-drained, rich in organic matter
• Deadhead spent blooms to encourage repeat flowering
• Divide clumps every 3 years to maintain vigor
USDA Zones: 5–9
Height: 45–60 cm (18–24")
Bloom Time: Late spring to early summer
Uses: Cottage gardens, pollinator beds, borders