How to Grow Delphiniums
Consolida ajacis
When to Start
Direct sow outdoors as soon as soil reaches 6°C — typically early to mid spring. Can also be started indoors 4 weeks earlier for a head start.
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Growth Stages
Approximate days from start
Care Essentials
- Light balanced feed at sowing. Rarely needs additional feeding.
- Excellent cottage garden annual. Sow direct — dislikes transplanting. All parts are toxic.
Companion Planting
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Growing Conditions
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- Sow indoors
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- Transplant out
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- First harvest
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Spacing & Planting
| Plant spacing | 20 cm |
| Row spacing | 30 cm |
| Sow depth | 0.5 cm |
| Mature height | 120 cm |
| Mature spread | 30 cm |
An annual delphinium relative. Closer spacing can help stems support each other. May require netting for very straight stems for cutting.
Care Guide
- Feeding
- Light balanced feed at sowing. Rarely needs additional feeding.
- Watch for
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- Slugs on seedlings
- Powdery mildew
- Aphids
Pests & Diseases
Pest Slugs and Snails
Identification: Seedlings eaten to ground level overnight, irregular holes in young leaves, slime trails
- Beer traps and copper tape barriers
- Nematode biological control (Nemaslug) applied in spring
- Evening hand-picking
- Ferric phosphate pellets (wildlife-safe)
Pest Aphids
Identification: Clusters of small green or black insects on shoot tips and flower buds, sticky honeydew, distorted growth
- Squash by hand or blast off with a strong jet of water
- Encourage ladybirds, lacewings, and hoverflies
- Soft soap spray
- Pyrethrum-based contact insecticide
Disease Powdery Mildew Erysiphe spp.
Symptoms: White powdery coating on leaves and stems, leaves yellow and drop prematurely
Treatment: Remove badly affected foliage. Improve air circulation by thinning plants.
Prevention: Space plants well. Avoid overhead watering. Grow in full sun with good airflow.
Disease Crown Rot Sclerotinia spp.
Symptoms: Blackened, mushy stem base, plant collapses suddenly, white fungal growth may be visible at soil level
Treatment: Remove and destroy affected plants. Do not replant in the same spot.
Prevention: Ensure excellent drainage. Avoid overwatering and overcrowding. Do not mulch tight against stems.
Growing Conditions
| Min. soil temperature | 6°C |
| Germination temperature | 12–18°C |
| Base growth temperature | 5°C |
| Min. daylength to start | 9h |
| Photoperiod sensitivity | long day |
Frequently Asked Questions
- How far apart should I plant Delphiniums?
- Plant Delphiniums 20cm apart with 30cm between rows.
- When does Delphiniums flower?
- Delphiniums typically flowers approximately 70 days after transplanting.
- Is Delphiniums frost hardy?
- Delphiniums is classified as Hardy.
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