How to grow leeks

Inspired by a helpful YouTube guide. We based this guide on the GrowVeg video "Growing Leeks from Sowing to Harvest", which takes you through every stage from sowing seed in modules to harvesting fat winter leeks. It is particularly good on the transplanting method, which trips a lot of people up the first time.

1. Sow seeds into modules in early spring

Sow from late February into small modules or a seed tray indoors. Sprinkle a few seeds per cell and cover lightly. They germinate at around 10–13°C, so a windowsill or cool greenhouse is fine — no need for a propagator.

Thin each cell to the strongest seedling once they are up. You are aiming for transplants roughly the thickness of a pencil before they go outside, which takes about eight to ten weeks.

2. Harden off before planting out

From May onward, start moving trays outside during the day and back in at night. Do this over a week or two. Leeks are tough, but a sudden move from warm windowsill to cold ground will check their growth noticeably.

Once they are acclimatised, they can go out permanently. Early varieties go in from May, maincrop ones anytime up to July.

3. Transplant using a dibber into deep holes

Make holes about 15cm deep and 15cm apart using a thick dibber or a piece of dowel. Drop one seedling into each hole. Do not fill the hole with soil — just pour water in gently. The soil will wash in naturally around the roots and the hole will slowly fill as the leek grows.

This is the traditional British method and it works. The stem blanches in the dark hole, giving you that long white shank that makes leeks so useful in the kitchen.

4. Earth up as the leeks grow

As the season progresses, pull soil up around the base of each leek to further exclude light and extend the blanched section. Do this gradually — a few centimetres at a time — and avoid getting soil into the centre of the plant.

Keep the bed weed-free. Leeks are slow growers and weeds will overtake them quickly if left unchecked.

5. Water in dry spells

Once established, leeks are fairly drought-tolerant. That said, a good soak every week or so in dry summer weather will help them put on size before winter arrives. Feed with a balanced fertiliser in mid-summer if growth looks slow.

Leek rust (orange powdery patches on the leaves) looks alarming but rarely causes serious harm. Remove affected leaves and ensure good air circulation. Mild varieties suffer less than maincrop ones.

6. Harvest from autumn through to spring

Leeks can be harvested any time from September, starting with the largest and leaving the rest to carry on growing. Ease them out with a fork rather than yanking — the roots grip firmly and the stem will snap if you are too aggressive.

Left in the ground, leeks will stand through hard frost without much fuss. That is the whole point of growing them: fresh vegetables throughout the coldest months when most other crops are finished.

When to call a handyman

Leeks are very much a grow-it-yourself project. If you need raised beds built, a vegetable patch cleared, or help installing a compost bin to feed the bed next season, Richard can help with any of that groundwork.