How to Grow Leeks
Allium ampeloprasum
Sow leeks indoors from January or outdoors from March, and transplant into deep 15 cm holes from late May onwards — water in without backfilling to blanch the stems. Space 12-15 cm apart in rows 25-30 cm apart. Cover with fine insect mesh to prevent leek moth and allium leaf miner. Leeks are very hardy and can be left in the ground all winter, lifting with a fork as needed.
When to Start
Direct sow outdoors as soon as soil reaches 6°C — typically early to mid spring. Can also be started indoors 9 weeks earlier for a head start.
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Growth Stages
Approximate days from start
Care Essentials
- Balanced fertiliser at planting. Liquid feed monthly during growing season.
- Plant in deep holes (15cm) and fill gradually to blanch the stems. Cover with fine mesh to prevent leek moth.
Growing Conditions
- Min. soil temperature
- 6°C+
- Germination temperature
- 12–22°C
Pet Safety
- Sow indoors
- —
- Transplant out
- —
- First harvest
- —
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Spacing & Planting
| Plant spacing | 12 cm |
| Row spacing | 25 cm |
| Sow depth | 1 cm |
| Mature height | 60 cm |
| Mature spread | 15 cm |
Transplant seedlings into deep holes to encourage long white shanks. Spacing allows for good stem thickness.
Pests & Diseases
Pest Leek Moth
Identification: Pale tunnels or mines in leaves, small cream-coloured caterpillars boring into the stem, frass visible at entry holes
- Cover with fine insect mesh from planting through to harvest
- Inspect plants regularly and remove caterpillars by hand
- Crop rotation to reduce local populations
- No effective chemical treatments available to home gardeners
Pest Allium Leaf Miner
Identification: Lines of white dots on leaves where adult flies have punctured, brown pupae inside stems, distorted and rotting plants
- Cover with insect mesh during the two flight periods (March-April and October-November)
- Crop rotation
- Remove and destroy affected plants
- No effective chemical treatments available to home gardeners
Pest Slugs and Snails
Identification: Irregular holes in leaves, slime trails, hollowed-out stems at soil level
- Beer traps and copper barriers
- Nematode biological control (Nemaslug)
- Evening hand-picking
- Ferric phosphate pellets (wildlife-safe)
Disease Leek Rust Puccinia porri
Symptoms: Bright orange pustules on leaves, heavy infections cause yellowing and dieback of foliage
Treatment: Remove badly affected outer leaves. Plants usually survive and remain edible.
Prevention: Space plants well for airflow. Avoid high-nitrogen feeds. Choose rust-resistant varieties. Rotate crops.
Disease White Tip Phytophthora porri
Symptoms: White, papery tips on leaves that gradually spread downward, leaves may become twisted
Treatment: Remove affected leaves. Improve air circulation.
Prevention: Avoid overhead watering. Space plants well. Rotate allium crops on a 3-year cycle.
Growing Conditions
| Min. soil temperature | 6°C |
| Germination temperature | 12–22°C |
| Base growth temperature | 5°C |
| Min. daylength to start | 8.5h |
| Photoperiod sensitivity | long day |
Frequently Asked Questions
- How far apart should I plant Leeks?
- Plant Leeks 12cm apart with 25cm between rows.
- When can I harvest Leeks?
- Leeks is ready to harvest approximately 120 days after transplanting.
- Is Leeks frost hardy?
- Leeks is classified as Hardy.
