Seed Treatment (Pre-Planting Preparation)
Cold Stratification:
- Mix seeds with moist sand or a damp paper towel.
- Place in a sealed plastic bag and refrigerate at 40°F (4°C) for 3–4 weeks.
- Check weekly to keep medium moist (not soggy).
- If seedlings sprout in the fridge, remove and plant immediately.
Alternative Natural Stratification:
- Sow seeds outdoors in late fall for natural cold treatment over winter.
Best Planting Time
Indoors: Start 6–8 weeks before last frost.
Outdoors: Sow directly in early spring or fall.
Soil Requirements
- Well-draining, moist, rich soil. Ideal pH 6.0–7.0.
- A mix of loam and compost works well.
Sunlight: Prefers partial shade. Tolerates full sun in cooler climates.
Planting Depth
- Surface sow — press seeds lightly into soil.
- Do not cover (light aids germination).
Spacing: 12–18 inches (30–45 cm) apart to allow airflow.
Watering: Keep soil evenly moist, not waterlogged. Use gentle misting spray to avoid disturbing seeds.
Temperature for Germination: 59–68°F (15–20°C).
Germination Time: 30–90 days after stratification.
Care After Germination
Thinning: When seedlings develop 2 sets of true leaves, space 12–18 inches apart.
Fertilization: Apply balanced liquid fertilizer every 4–6 weeks.
Mulching: Use a thin layer of organic mulch to retain moisture and suppress weeds.
Deadheading: Remove spent flowers to encourage more blooms and control self-seeding.
Winter Care: In cold regions, mulch lightly to protect roots. Columbine often self-seeds naturally.