Planting Out Leeks in the UK: The Complete Guide to Transplanting Leek Seedlings
Introduction
If you’ve grown leek seedlings indoors or in modules, it’s time for the next stage — planting them out into your garden, raised bed, or allotment. This crucial step determines whether your leeks grow into strong, thick, white stems… or end up thin and spindly.
In the UK, leek seedlings are typically planted out between late April and early July, depending on when they were sown. And with a few simple steps — especially the traditional dibbing method — you can ensure your leeks grow tall, tasty, and perfect for harvesting from autumn right through winter.
This article will guide you through exactly how to plant out leeks in the UK, including spacing, soil prep, watering, and top tips for leek-growing success.
When to Plant Out Leeks in the UK
Leek seedlings are ready to transplant when:
- They are about 6–8 inches (15–20cm) tall
- The stems are roughly pencil thickness
- Soil temperatures are above 10°C (usually late April to early July)
Avoid planting out during frost or heatwaves — choose a mild, overcast day for best results.
Where to Plant Leeks
Leeks prefer:
✅ Full sun or partial shade
✅ Free-draining but moisture-retentive soil
✅ Soil that has been well-dug and enriched with compost or rotted manure (added at least 6 months prior)
Avoid planting in freshly manured soil — this can cause misshapen stems.
How to Prepare the Soil
- Clear the bed of weeds and debris
- Rake in some general-purpose organic fertiliser (e.g. growmore, chicken manure pellets)
- Lightly rake the surface level
- Water the bed a day or two before planting to ensure moisture is present
No need to over-fertilise — leeks don’t like rich, overly nitrogenous soil at transplant time.
Tools You’ll Need
- Garden dibber or wooden stake
- Watering can
- Garden fork (to lift seedlings)
- Gloves and trowel (optional)
Step-by-Step Guide: Planting Out Leeks
🌱 Step 1: Prepare the Seedlings
- Water the leek tray well before planting to reduce stress
- Carefully tease seedlings apart
- Trim long roots and leaf tips (optional but traditional) to reduce transplant shock
🌿 Step 2: Dib and Drop
The famous “dib and drop” method is what makes British leeks so beautifully white and long-stemmed.
- Use a dibber to make deep holes 15–20cm (6–8″) deep and spaced 15cm (6″) apart in rows 30cm (12″) apart
- Drop one seedling into each hole
- Do not fill in the hole with soil — instead, water into the hole. This washes soil in gently around the roots while leaving space for the stem to expand
This allows the white stems to self-blanch as they grow.
Aftercare: Watering, Feeding & Maintenance
| Task | Tip |
|---|---|
| Watering | Water regularly during dry spells |
| Mulching | Apply straw or compost to retain moisture and reduce weeds |
| Feeding | After a few weeks, feed with seaweed feed or diluted comfrey tea |
| Weeding | Keep bed clear — leeks don’t like competition |
Once established, leeks are very low maintenance.
Optional: Earthing Up
If you want extra-long white stems:
- As the leeks grow, gently draw soil around the base
- Do this gradually over time
- Be careful not to get soil trapped between leaves — it can be hard to wash out later
This step is not essential, especially if using the dibbing method, but it’s useful if you want show-worthy leeks.
Can You Plant Out Supermarket Leeks?
Some gardeners root leftover supermarket leeks and plant them out — but results vary. For a strong crop, it’s best to use:
- Sown seedlings
- Plug plants from garden centres
- Transplants from your own trays
These give you reliable, disease-free results.
Companion Plants for Leeks
Leeks grow well with:
- Carrots (repels carrot fly)
- Celery, onions, and brassicas
- Beetroot and lettuce (good for interplanting)
- Strawberries (deters pests)
Avoid planting near legumes like peas or beans, which don’t get along with alliums.
Common Problems When Planting Out Leeks
| Problem | Cause | Solution |
|---|---|---|
| Leeks going limp | Planted in dry or hot conditions | Water well and plant during cool weather |
| Thin stems | Overcrowding or nutrient deficiency | Thin seedlings, feed regularly |
| Rust (orange spots) | Fungal disease, especially in wet weather | Remove affected leaves; improve airflow |
| Allium leaf miner | Larvae in stems, causes distortion | Use mesh or fleece in spring and autumn |
Regular checks and good hygiene will prevent most issues.
How Deep Should You Plant Leeks?
Plant in 15–20cm deep holes to allow for self-blanching. This helps develop:
- Longer white stems
- Tender flavour
- Protection from weather extremes
Deeper holes = better leeks!
Can You Plant Leeks Straight from Seed Outdoors?
Yes — but they’ll be slower to grow and more vulnerable to slugs and weeds. For best results:
- Sow in nursery rows, then transplant
- Or start indoors and plant out stronger seedlings
Direct sowing works best in mild southern climates or during warm springs.
When Will My Planted-Out Leeks Be Ready to Harvest?
Leeks take 5–7 months from seed to maturity. If planted out in May/June, expect to harvest:
| Transplanted | Ready to Harvest |
|---|---|
| May | September–December |
| June–July | November–March (overwintering) |
Pick gradually as needed — they store well in the ground.
Can You Grow Leeks in Raised Beds?
Absolutely! In fact, raised beds often offer:
✅ Better drainage
✅ Fewer weeds
✅ Easier dibbing
✅ Controlled soil quality
Ideal for small gardens or clay-heavy soil.
Conclusion
Planting out leeks is a rewarding mid-spring to early summer job that sets your garden up for a reliable autumn-winter harvest. Whether you’re growing Musselburgh or Porbella, using the traditional dibber method will help you produce thick, flavourful leeks perfect for soups, pies, and casseroles.
With just a little soil prep and aftercare, your leeks will thrive — even through frost and snow. It’s a must-grow crop for any UK kitchen gardener or allotment holder.
Top 10 Questions and Answers About Planting Out Leeks
1. When should I plant out leeks in the UK?
From late April to early July, depending on the weather and seedling size.
2. How deep should I plant leek seedlings?
15–20cm deep using the dibbing method.
3. Do I fill in the holes after planting?
No — just water them in. The soil settles naturally.
4. How far apart should I space leeks?
15cm between plants in rows 30cm apart.
5. Should I trim the roots and tops?
You can — it helps reduce transplant shock, but it’s optional.
6. Can I plant supermarket leeks?
You can root and try, but results aren’t as reliable as proper seed-grown plants.
7. Do leeks need a lot of feeding?
Not much — just a liquid feed every few weeks after they settle in.
8. Can I grow leeks in containers?
Yes — as long as the container is deep (30cm+) and well-drained.
9. Do leeks survive frost?
Yes — they’re one of the hardiest winter veg and can be left in the ground.
10. How do I know when my leeks are ready?
When stems are 2–3cm thick and at least 15cm long — lift with a fork, not by hand.