How to Grow Sweet Peas
Lathyrus odoratus
Sweet peas are cool-loving annual climbers for full sun and rich, well-drained soil. Sow in autumn under cover or in spring, using deep pots; pinch seedlings to branch. Plant out with sturdy netting or canes and tie in regularly. Keep soil evenly moist and pick flowers every two days to prolong bloom; remove seedpods promptly. Avoid high nitrogen, which promotes leaf at the expense of flowers. Fragrant varieties excel in open, sunny spots with good airflow.
When to Start
Direct sow outdoors as soon as soil reaches 5°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
- High-potash liquid feed weekly once flowering starts.
- The more you pick, the more they flower. Soak or nick seeds before sowing. Need a tall support (1.8m+).
Growing Conditions
- Min. soil temperature
- 5°C+
- Germination temperature
- 12–18°C
Pet Safety
- Sow indoors
- —
- Transplant out
- —
- First harvest
- —
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Spacing & Planting
| Plant spacing | 15 cm |
| Row spacing | 45 cm |
| Sow depth | 2 cm |
| Mature height | 200 cm |
| Mature spread | 30 cm |
A climbing annual. Space seeds along the base of a support structure (trellis, netting, or teepee). Sowing in a zig-zag pattern gives a denser display.
Pests & Diseases
Pest Aphids
Identification: Clusters of green or black insects on growing tips, tendrils, and flower buds; sticky honeydew; distorted growth; sooty mould
- Blast off with a jet of water
- Spray with insecticidal soap, targeting shoot tips and undersides of leaves
- Encourage ladybirds, lacewings, and hoverflies
- Spray with a systemic insecticide containing acetamiprid; avoid spraying open flowers to protect pollinators
Pest Slugs and Snails
Identification: Seedlings eaten at ground level; ragged holes in young leaves; slime trails on foliage and around pots
- Apply organic slug pellets (ferric phosphate based) around seedlings
- Use copper tape around pots and containers
- Hand-pick at dusk; use beer traps
- Apply ferric phosphate slug pellets around vulnerable plants
Pest Mice
Identification: Seeds disappear from pots or drills; disturbed soil where seeds were sown; seedlings nipped off at ground level
- Cover seed trays and pots with fine mesh or chicken wire until seedlings are established
- Sow in a greenhouse or on a high shelf away from mouse access
- Set humane traps near sowing areas
Disease Powdery Mildew Erysiphe pisi
Symptoms: White, powdery coating on leaves and stems; leaves yellow and die back; flowering declines
Treatment: Remove badly affected leaves; spray with a sulphur-based fungicide or potassium bicarbonate solution
Prevention: Space plants for good airflow; water at the base; avoid overhead watering; keep roots cool with mulch
Disease Foot Rot Fusarium spp.
Symptoms: Dark, water-soaked lesions at the base of stems; plants wilt and collapse; roots may be brown and rotting
Treatment: Remove and destroy affected plants; improve drainage; avoid overwatering
Prevention: Use clean compost for sowing; avoid waterlogged soil; rotate planting positions; do not sow too deeply
Disease Pea Mosaic Virus Pea seed-borne mosaic virus
Symptoms: Mottled, streaked leaves with yellow and green patterns; stunted growth; flowers may show colour-breaking streaks
Treatment: No cure — remove and destroy infected plants to prevent spread
Prevention: Control aphids which spread the virus; remove infected plants promptly; do not save seed from affected plants
Growing Conditions
| Min. soil temperature | 5°C |
| Germination temperature | 12–18°C |
| Base growth temperature | 4°C |
| Min. daylength to start | 9h |
| Photoperiod sensitivity | long day |
Frequently Asked Questions
- How far apart should I plant Sweet Peas?
- Plant Sweet Peas 15cm apart with 45cm between rows.
- When does Sweet Peas flower?
- Sweet Peas typically flowers approximately 70 days after transplanting.
- Is Sweet Peas frost hardy?
- Sweet Peas is classified as Hardy.
