How to Grow Leek
Leek At a Glance
Difficulty
Moderate
Category
Vegetable
Sun Exposure
Full Sun, Partial Sun
Frost Tolerance
Frost Hardy
Cold Hardiness
Survives to -18°C
Plant Family
Amaryllidaceae
Growing Season
Cool Season
Plant Lifecycle
Biennial
How to Start It
★ Recommended for beginners
Leeks need a long, slow season to grow thick stems, longer than most of our summers allow from an outdoor sowing, so start them inside. Sow seeds 1 cm deep in a deep tray about 8 weeks before your last frost, and they sprout in 7 to 14 days; trim the leaves to about 10 cm with scissors if they flop. Plant them out about 4 weeks after your last frost, once they are about as thick as a pencil: drop each one into a 15 cm deep hole made with a stick, 15 cm apart, and fill the hole with water only, not soil. Before planting out, set the pots outside in a sheltered spot for a few hours a day, a little longer each day for about a week, so they toughen up (this is called hardening off).
Leeks are slow, but they are hardy and easy, and they can stay in the ground well into fall and early winter, ready to pick whenever you need one. Planting them deep is what gives you a long, white, tender stem.
When To Start
First chance to plant
60 Days Before Last Frost
Last chance to plant
60 Days Before First Frost
When should you plant Leek?
Your planting dates depend on your local climate. Sign up and add your location to unlock personalized dates.
Your Leek Planting Window
Start planting
May 15, 2026
Last chance
Sep 10, 2026
Your Leek Calendar
Set your location to turn these into exact dates and reminders.
Start leek seeds indoors in a deep tray
8 weeks before your last frost· every year
Plant pencil thick leeks into deep holes, then water in
30 days after your last frost· every year
Pull leeks as you need them, even after frost
Around your first frost· every year· optional
Start hardening off your leek seedlings: an hour outside today, a little longer each day.
20 days after your last frost
Water your new leek plants well while they settle in. Deep and slow is best.
About 1 days after you plant it
Your leeks are on their way! Keep the soil evenly damp and pull any weeds that crowd the young stems.
About 54 days after you plant it
Nice work so far! Pile a little soil around the stems to keep more of each leek white and tender.
About 94 days after you plant it
Picking time may be here: check your leek.
About 120 days after you plant it
The Journey Ahead
Leek's Lifecycle
Seedling
Mature Plant
Seed Production
Step 2
Planting & Sprouting
Expect sprouts in 7–14 days
Growing Tips
- 1Grow leeks in full sun, at least 6 hours a day.
- 2Mix plenty of compost into the soil, since leeks are hungry and grow for months.
- 3Water deeply about once a week so the soil never dries out, and feed with worm castings or compost tea every 3 to 4 weeks through summer.
- 4As they grow, pile soil or straw up around the stems a few times (this is called hilling) to keep more of each stem white and mild.
- 5Cover young plants with row cover to keep off the small flies and moths whose grubs tunnel into the stems.
- 6Leeks, like onions, are toxic to cats and dogs, so keep chewing pets away.
Seedling Phase
Step 3
Growth & Maturity
~120
Days to Maturity
45 cm
Mature Height
5 cm
Mature Width
Pests to Watch For
Diseases to Watch For
Mature Plant
Step 4
Harvesting
Harvest Window
45 days
When to Pick
Pull when stalks are thick and base is swollen
How to Harvest
- 1Start pulling leeks when the stems are about 2 to 3 cm thick, from late summer on.
- 2Loosen the soil beside each leek with a fork first, then lift it out, since pulling by the leaves snaps them.
- 3Leave the rest in the ground and pick as needed, since leeks handle hard frost, and cover them with straw to keep digging some into early winter.
- 4Trim the roots and the dark green tops, then slice the stem lengthwise and rinse out the soil hidden between the layers.
- 5Keep leeks unwashed in the fridge for 1 to 2 weeks.
Step 5
Saving Seeds
How to Save Seeds
Leeks are biennial: they only flower and make seed in their second summer. In mild areas, leave a few of your best plants in the ground over winter under a thick layer of straw; in cold areas, dig them up in fall, pot them, and keep them somewhere cold that does not freeze, then replant in spring. Bees cross leeks with other leeks (not with onions), so let only one variety flower within about 800 m, and let at least 6 plants flower together. Hybrid F1 seeds will not grow true, so save only from a variety that is not a hybrid. When the big round flower heads turn dry and papery and you see black seeds, cut them into a paper bag and dry them for another 2 weeks. Rub out the seeds and store them labelled in a cool, dark, dry place, where they keep about 2 to 3 years.
Seed Production
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