How to Plant Dahlia Seeds
When to Start
- Indoors: Start seeds 6–8 weeks before your last frost date.
- Outdoors: Sow directly after all danger of frost has passed and soil is warm (not recommended in short-season climates — indoor starting gives much better results).
Materials Needed For Starting Indoors
- Seed-starting trays or small pots
- Seed-starting mix (light, well-draining soil)
- Spray bottle or gentle watering can
- Grow lights or bright sunny location
- Plant labels (highly recommended)
Steps for Starting Indoors
1. Fill Trays With Seed-Starting Mix
- Lightly moisten the mix before filling trays.
2. Plant Seeds Shallowly
- Sow seeds ¼ inch deep. 1 seed per cell.
- Gently press soil over seeds.
- Mist soil to dampen evenly
- cover with plastic dome to retain moisture. Leave on until seeds sprout.
3. Provide Warmth & Light & Water
- Ideal temperature: 70–75°F (21–24°C) for germination.
- Provide bright light or grow lights for 12–14 hours per day once seedlings emerge. I use shop lights - nothing fancy.
- Airflow is key when planting inside. I keep an oscillating fan on them during the day. This also helps strengthen the stems.
- Water from the bottom to avoid damping-off.
4. Harden Off
- 1 week before planting outside: Get seedlings used to outdoor life (start with shade, then move to sun).
Planting Outdoors
- Full sun (at least 6 hours/day)
- Well-draining soil, enriched with compost
- Spacing: 12–18 inches apart. If you are short on space you can plant them closer and cull the ones you do not want.
- Plant seedlings at the same depth as in pots.
- Water well after planting.
Ongoing Care
| Need | Details |
|---|---|
| Water | Keep soil evenly moist, avoid soaking |
| Feeding | Start feeding with a balanced flower fertilizer 2–3 weeks after transplant |
| Support | Taller varieties may need staking |
| Deadheading | Remove spent blooms to encourage more flowers |