When to plant leeks?
Leeks are sown outdoors mainly in March and April, and in May and June for varieties that carry into winter and spring, while indoors they start from late winter above 10 °C. Umbria's guide sets no month and asks for at least 2 years with no other alliums; Campania and Sicily do not write a sowing date.
When, by region
| North | Centre | South | |
|---|---|---|---|
| Sowing | Outdoors, the main months are March and April. May and June for later varieties, to harvest in winter and spring, and for baby leeks. Indoors from late winter, about 1.5 cm deep, above 10 °C. Outside after about 8 weeks, at 20 cm tall. | Umbria's 2025 guide does not fix a month. No repeat crop: at least 2 years, and no other alliums in between. | Campania points to the national guidelines and writes no month. Sicily's guide has no leek sowing chapter. |
| Spacing | Transplant at 20 cm, pencil thick. Holes 15 cm deep and 5 cm wide, 15-20 cm apart, or 10 cm for baby leeks. Rows 30 cm apart. Trim the roots to 2.5 cm. In a pot about 40 cm wide, four or five plants. | As in the north. Umbria does not write a spacing. | As in the north, until a southern guide writes its own spacing. The 10 °C threshold is the RHS one for indoor sowing, not a Campania or Sicily figure. |
A cold spell on an early sowing sends the plants to flower. Winter leeks stay in the ground with no cover.
March and April, May and June, indoors from late winter, 10 °C (50 °F), 1.5 cm, the 8 weeks, 20 cm, holes 15 cm deep, 15-20 cm, 10 cm for baby leeks, 30 cm, 2.5 cm and a 40 cm pot are from the RHS. The 2 years with no other alliums, and the lack of a month, are from Umbria's 2025 sheet. Campania's leek page does not fix a date. Sicily's guide has no sowing chapter. Garlic, in the same family, is in when to plant garlic. The months are in the February calendar, March, April, May and June.
March and April, then the later ones
The RHS sows outdoors in March and April, in a seedbed or in place. Later varieties, for winter and spring, and fast ones for baby leeks, go in during May and June. The drill is about 1.5 cm (¾ in) deep, rows 30 cm (1 ft) apart. A cold spell on an early sowing makes them bolt: cover with a cloche or fleece. Indoors, from late winter, keep the compost above 10 °C (50 °F). After about 8 weeks, at 20 cm (8 in), plant them out.
Transplant when the plant is 20 cm tall and pencil thick. The hole, made with a handle, is 15 cm (6 in) deep and 5 cm (2 in) wide. Do not backfill it: fill it with water, and the soil settles on its own. Trim the roots to 2.5 cm (1 in). In the row, 15-20 cm (6-8 in), or 10 cm (4 in) for baby leeks. The seedbed is in the homemade seedbed.
South and centre, with no month
Campania, on the leek sheet, points to the national guidelines for cultivation and writes neither a month nor a degree threshold. Sicily's guide has no leek sowing chapter. Where the regional month is missing, the RHS window and the packet still apply.
In Umbria, in 2025, leeks are not repeated. At least 2 years pass between crops, and no other alliums go in between, because of nematodes, Fusarium and Sclerotinia. A sowing month, on that sheet, is not there. Onion and garlic, same family, are in when to plant onions and when to plant garlic.
The white shank, water, winter
The long white shank comes from the deep hole and from earthing up, several times, without letting soil into the leaves. Water until the plant has roots. Then only in long dry spells, at the base, because water on the leaves encourages rust. How much is in watering. Baby leeks are ready in a couple of months. Full-sized ones take about six months, and are lifted with a fork from late summer. Later varieties stay in the ground through winter and into spring, with no cover: frost, the RHS writes, can sweeten them.
A pot about 40 cm (16 in) wide holds four or five mature plants, with the same holes. The compost dries out all season. See the container garden. They sit with onions and garlic in crop rotation. If a flower stalk appears, cut it at once, or the shank turns fibrous. Rust and insects are in pests and diseases.
In the app
Every plant in the catalogue has its own sowing calendar, and weather alerts for your area help you judge whether to sow now or hold off.
Frequently asked questions
When do I sow in the north?
Outdoors in March and April. In May and June, the later varieties, for winter and spring, and the baby-leek varieties. Indoors from late winter, above 10 °C, and out after about 8 weeks, at 20 cm.
What month is written in the south?
None. Campania does not fix a date. Sicily has no sowing chapter. In Umbria the month is missing too: at least 2 years, and no other alliums in between.
How do I get a long white shank?
The RHS makes holes 15 cm deep and 5 cm wide, fills them with water rather than soil, and earths up several times without letting soil into the leaves. Roots are trimmed to 2.5 cm.
How far apart, and in a pot?
15-20 cm in the row, rows 30 cm apart. For baby leeks, 10 cm. In a pot about 40 cm wide, four or five plants. Seed goes about 1.5 cm deep.
Do they stay outside in winter?
Later varieties do. The RHS leaves them in the ground into spring, with no cover, and lifts them as needed. Frost can sweeten them. Early ones are lifted from late summer.