How to Grow Larkspur
Consolida ajacis
Larkspur (annual Consolida) is a hardy annual that prefers full sun and well-drained, alkaline to neutral soil. It dislikes transplanting, so direct sow in autumn or early spring where winters are mild/cool. Thin for airflow and stake lightly in windy spots. Water during dry spells but avoid rich feeding, which causes flopping. For cut flowers, harvest when the lower third of florets have opened. All parts are toxic—site away from pets and children.
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.
Growing Conditions
- Min. soil temperature
- 6°C+
- Germination temperature
- 12–18°C
Pet Safety
- Sow indoors
- —
- Transplant out
- —
- 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.
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 Larkspur?
- Plant Larkspur 20cm apart with 30cm between rows.
- When does Larkspur flower?
- Larkspur typically flowers approximately 70 days after transplanting.
- Is Larkspur frost hardy?
- Larkspur is classified as Hardy.
