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
Soak seeds in lukewarm water for 6–8 hours before sowing.
When to Sow
Indoors: Start seeds 6–8 weeks (42–56 days) before your last expected frost.
Outdoors (for natural stratification): Direct sow in autumn in mild climates or early spring in cooler areas once soil is workable.
Optimum Germination Temperature: Use a heat mat to maintain steady temperatures of 18–22°C (65–72°F)
Germination Time: up to 21 days
Light Requirements for Germination
Needs light to germinate. Surface sow—do not cover with soil.
Use grow lights to maintain 12–16 hours of light per day.
How to Sow Indoors
- Use a fine, well-draining seed-starting mix in trays or small pots.
- Gently press seeds into the surface of pre-moistened soil without covering them.
- Mist lightly to avoid displacing the seeds.
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
- Once seedlings develop 2–3 true leaves, transplant them to individual pots or harden off before moving outdoors.
- Final spacing: 20–30 cm (8–12 in) apart
- Type: Hardy annual
- Mature height: 30–45 cm (12–18 in)
- Prefers full sun and well-draining soil. Avoid overwatering.
- Deadhead spent blooms to encourage prolonged flowering.