How to Plant, Grow, and Harvest Leeks


Leeks are grown for their thick, juicy, long stalks. They are a mild-flavored alternative to the onion. Leeks require a long growing season—up to 170 days. They grow best in cool, mild weather.

Leeks belong to the Allium family which includes onions, shallots, scallions, and garlic. Leeks don’t grow from bulbs like other Alliums, they grow thick, cylindrical white stalks. Above the stalks are fans of flat, blue-green leaves. Both the stalks and leaves are edible.

Leeks can be eaten raw in salads, added to soups or stews, or sautéed as a vegetable side dish. Leeks are most notably used in potato and leek soup, which when chilled is known as vichyssoise. The stalks are the main crop, but the leaves can also be used in soups and stews.

Short-Season and Long-Season Leeks

  • Long-season leeks have thick, cylindrical stems. They take about 120 to 170 days to reach harvest. Long-season leeks are usually planted in spring and are harvested from late summer through the winter. Mature leeks are frost-tolerant. They can be stored in the garden through the winter under heavy mulch. They also store well in a root cellar. Long-season varieties include ‘Bandit’, ‘Comanche’, ‘Carentan’, ‘Giant American Flag’, ‘Giant Musselburgh’, and ‘Runner’.
  • Short-season leeks–also called “early season” leeks–have thin stems and are generally smaller than long-season varieties. They mature in 50 to 120 days. Short-season leeks are commonly planted in spring and are harvested during the summer or early autumn. They are less hardy than long-season leeks. Short-season varieties include ‘King Richard’, ‘Lancelot’, ‘Rally’, and ‘Varna’. Plant short-season leeks where the growing season is short.
  • Sometimes short- or long-season leek varieties that mature in 90 to 120 days are referred to as “mid-season” leeks.
  • Choose a variety according to the time of year you want to harvest leeks.

Where to Plant Leeks

  • Grow leeks in full sun. Leeks will tolerate partial shade.
  • Leeks grow best in well-drained soil rich in organic matter. Add a couple of inches of aged compost or commercial organic planting mix to the planting bed in spring ahead of planting. Turn the soil to 12 inches deep.
  • A soil pH of 6.0 to 6.8 is best for leeks.
  • Grow leeks where legumes have recently grown. They will benefit from nitrogen in the soil.
  • Leeks are often sown or transplanted into trenches. Trench-planting is a way to blanch the stems making them more tender and flavorful.
  • Prepare trenches 6 to 8 inches (15-20cm) deep and 4 to 6 inches (10-15cm) wide. Seedlings will be transplanted to the bottom of the trench. As plants grow backfill soil in around the plants until the trench is eventually filled.
  • Leeks can be planted in soil-level beds. Mound up surrounding soil or mulch to blanch leeks in soil-level beds.
  • The stems of leeks also can be blanched by wrapping paper or plastic tubes around the stems.
Leeks planted in garden
Leeks require 120 to 170 days to come to harvest and grow best where the temperature ranges from 55° to 75°F (13-24°C).

Leeks Planting Time

  • Leeks require 120 to 170 days to reach harvest depending on the variety.
  • Leeks grow best in temperatures between 55° and 75°F (13-24°C). Growth will be slowed by hot weather. Begin sowing leek seeds in the garden not later than mid-spring.
  • Leek seeds germinate in soil that is 65°F, but the optimal germination temperature is between 70° and 75°F.
  • Grow leeks from transplants started indoors or from seeds sown directly in the garden.
  • In mild winter climates, start leeks indoors or direct sow seeds in the garden 12 weeks before the first frost in autumn for harvest in autumn or late winter.
  • Leeks can tolerate warm temperatures but growth will be slowed.
  • Mature leeks can tolerate cold and will survive under an insulating blanket of snow.
  • Plant 12 to 15 leeks per household member.

Starting Leeks from Seed Indoors

  • Starting leeks indoors: Sow leek seeds indoors in early spring; start seed indoors 10 to 6 weeks before the last expected spring frost.
  • Start leeks indoors in a sterile, seed-starting mix; use a cell tray of 6-packs. Plant a few seeds per cell. Sow seeds ¼ to ½ inch (12mm) deep.
  • Seeds will germinate in 10 to 14 days at 70°F (21°C).
  • Keep seedlings under grow lights for 12 to 16 hours a day until they are transplant size, about 6 inches tall. Gently separate clusters or clumps of seedlings before transplanting.
  • Transplant leek seedlings into the garden as early as 4 to 5 weeks before the last expected spring frost when they are about 4 to 6 inches (10cm) tall. Transplants should be in the garden no later than early summer for autumn harvest.
  • To encourage stocky stem growth, keep the tops of seedlings started indoors to 4 inches (10cm) tall until they are transplanted into the garden.
Mature leeks can tolerate cold and will survive under an insulating blanket of snow.
Mature leeks can tolerate cold and will survive under an insulating blanket of snow.

Planting and Spacing Leeks

  • Sow leek seeds ¼ to ½ inch (12mm) deep. Cover seed lightly with soil.
  • Seeds germinate in 10 to 14 days at 70°F (21°C).
  • Thin or transplant leeks to 4 to 6 inches (10-15cm) apart. Space rows 12 to 16 inches (30-40cm) apart.
  • Stagger-plant leeks in double rows; this will give fanning leaves more room to grow.
  • Leeks can be sown or transplanted into trenches 5 to 6 inches (12-15cm) deep. Trench planting allows for back-filling soil around the stems as they grow; this is one method of blanching the stems. (Blanched stems will be white and tender.)
  • If you transplant a seedling into a trench, continuously backfill the soil to cover all but the top 1 or 2 inches (2.5-5cm) of leaves. Do not backfill soil more than 1 inch at a time; filling in soil too quickly can cause stems to rot. Use a trowel or your hands to gently backfill soil around the stalks.
  • Trenches are gradually filled in over the course of the growing season.
  • Do not backfill or mound soil over the point where leaves start to branch out from the stems; stay below branching.
  • An alternative to backfilling soil is to blanch leek stalks by wrapping brown paper or cardboard around the stalks and tying the material in place loosely; this method will also work to blanch the stalks. You can also place plastic or cardboard tubes around the stalks. Slip 6-inch tubes of cardboard (paper towel or toilet paper tubes) or plastic (such as thin-walled, 2-inch, PVC pipe) over the stalks when they are almost an inch thick.
  • You can also allow watering to naturally collapse the soil around plants filling in the trenches.

Container Growing Leeks

  • Leeks can be grown in a 6- to 8-inches deep container. Space plants 4 inches apart.
  • Leeks growing in containers will likely not reach full size.
  • Grow leeks in a potting mix rich in garden compost. Ask at the garden center for recommended potting soil.
  • Rather than hilling soil up around each leek plant to blanch the stems, set cardboard or plastic tube around each stalk to exclude sunlight.
  • Use your finger or a dibber to create holes for transplants.
  • You can also wrap newspaper or cardboard around the stalks in order to blanch them.
  • As young plants grow and the stalks elongate you will need to increase the length of the tube or material surrounding the stalks.

Companion Plants for Leeks

  • Plant leeks with carrots, celery, garlic, and onions.
  • Leeks are often planted near carrots because they repel carrot flies.

Watering Leeks

  • Keep the soil around leeks evenly moist; water when the surface becomes just dry.
  • Leeks need about an inch of water each week. During dry spells, monitor the soil conditions and moisture carefully. Stick your index finger into the soil, if it comes away dry, water the plants.
  • It is best to water leeks at the base of the plant so as not to splash soil into the crevices between the overlapping leaves. Overhead watering can also leave leek susceptible to fungal disease.

Feeding Leeks

  • Prepare planting beds with well-aged manure and aged compost in advance of planting.
  • Leeks need a steady supply of nitrogen as they grow in order to reach full size.
  • Begin feeding leeks about 4 weeks after sowing seeds and continue feeding each month until harvest.
  • Fertilize leeks with compost tea, dilute fish emulsion, dilute seaweed extract, cottonseed meal, and other nitrogen fertilizers. An organic balanced fertilizer of 10-5-5 can be used.
  • Feed plants with compost tea every four weeks during the growing season.
Blanching leeks
Leeks growing in plastic pipes to blanch and extend the stems

Caring for Leeks

  • To grow large, white, succulent leeks, blanch the lower part of the stem by hilling up soil or mulch around stalks to exclude the light as they develop. You can also allow trenches to simply collapse around the stems. Blanching will make the stalks longer and tender.
  • Hill up around stalks to just below the leaf junction. Do not add soil higher than the leaf junction; this will help prevent soil and grit from lodging between leaves and stems.
  • Add 12 inches or more of straw above plants when the weather nears freezing. Leeks must be protected from freezing temperatures.
  • Mulch between rows and weed regularly, especially early in the season. Weeds compete with leeks for moisture and nutrients.
  • Leeks can bolt if there is too little soil moisture or too much phosphorus in the soil. Prolonged temperature below 45°F can cause leeks to bolt.

Leeks Pests

  • Onion thrips are tiny yellow-brown insects that suck juices from plants. They may attack leeks in dry weather. Hose thrips off of plants. Onion thrips suck juices from leaves causing the leaves to be silvery or rusty-streaked. Spray plants with water to wash off thrips or spray with neem oil. Beneficial insects such as lacewing larvae and predatory thrips will ear onion thrips.
  • Onion maggots (the larvae of a fly) can attack leek shanks and roots. Onion maggots are small white larvae that feed at the base of the plant, tunneling into the stalk. Cover plants with floating row cover to prevent flies from laying eggs. Beneficial nematodes will kill onion maggots.
  • Allium leaf miners are fly-like pests that feed on plant sap and lay eggs on the leaves. They can be controlled with neem oil or by beneficial insects.

Leeks Diseases

  • Leeks have can be attacked by fungal diseases rust and downy mildew.
  • Do not overhead water leaks.
  • Spray-mist plants with compost tea which is an anti-fungal or get an organic fungicide at the garden center.
Leeks can be harvested as soon as they are big enough to use.
Leeks can be harvested as soon as they are big enough to use.

Harvesting Leeks

  • Harvest leeks as soon as they are big enough to use or wait until they reach mature size. Leeks can be harvested when they are scallion or shallot-size.
  • Leeks will be near their mature size when stems reach 1 to 2 inches (2.5-5cm) in diameter and leaves are 12 to 18 inches (30-45cm) tall.
  • To encourage full stalk growth, cut off the top half of the leaves about midsummer.
  • The flavor of leeks is improved after plants are hit by a light frost.
  • Lift leeks as you need them through winter but complete the harvest before the ground freezes.
  • Do not wash leeks until you are ready to use them.

Storing Leeks

  • Keep leeks in the garden until you are ready to use them.
  • Rinse between leaves and stems to remove soil and grit.
  • Leeks will keep in the refrigerator in a plastic bag for up to one week or in a cold, moist place for 2 to 3 months.
  • You can keep leeks in moist sand or soil in a cool place–32 to 40–for six to eight weeks.
  • When freezing weather arrives, leeks can be dug from the garden and stored in cool–32°F to 40°F–and moist place.
  • Leeks can be stored upright in a box with the roots set in moistened sand or soil and then stored in a cool cellar.
  • Leeks can be kept in the garden over winter and survive a hard freeze if heavily mulched. Leeks are biennials; if leeks are left in the garden until spring they are likely to develop seed heads which will compromise the flavor.

Leeks in the Kitchen

  • Leeks can be served raw or cooked. Fresh leeks are milder flavored than onions and shallots.
  • The topmost leaves are usually tough; discard the tops or add them to a stockpot or something that will be boiling for a long time.
  • Wash leeks carefully before using to get rid of any dirt that got into the tops; you can cut the leek in half from root to top and then hold it under running water or swish it in a pan of water, pulling the layers apart and rinsing as you go. Then shake dry.
  • Raw, finely chopped leeks are often added to salads–use in combination or as a substitute for onions, shallots, or chives.
  • Young leeks can be served like scallions or spring onions.
  • Leek greens are often used to flavor quiche, broth, stews, and purees.
  • Steam of braise leeks and ser chilled in a salad.
  • Sautée thinly slice leeks by cooking them over low heat with thinly sliced mushrooms.
  • Leeds can be boiled until tender; serve them with melted butter.
  • Cut the white part of the leek into thin slices and precook by frying before adding it to a soup.
  • Leeks are rich in vitamins–vitamins K, B6, and C–and minerals including manganese and iron. Leeks also contain flavonoid antioxidants.

How to Extend the Harvest

  • Mulch spring-planted, slow-growing leeks with a thick layer of straw in late autumn for harvest through the winter.
  • Sow slower-growing varieties in summer for an early spring harvest.
  • Sow fast-growing varieties in winter in a plastic tunnel or cold frame for spring harvest.

Saving Leek Seeds

  • Leeks are biennial.
  • Overwinter leeks in the garden; in the second year they will raise a seed stalk that bees can pollinate.
  • Leeks are best isolated from other alliums if you intend to save seed and want them to breed true.
  • Leek seeds are viable for about 3 years.

Leeks Frequently Asked Questions

Q: Are leeks hare to grow?

A: Leeks require a long period to reach maturity, but they are simple to grow. Their culture takes more attention than skill.

Q: Should I start leeks indoors?

A: If you have a short growing season, start leeks indoors. Sow seed indoors 12 weeks before the last frost in spring. Thin sprouts to 1 inch apart. When leeks are pencil thin, transplant them into the garden 4 to 6 inches apart.

Q: Can I grow leeks in a mild winter region?

A: Yes, start leeks outdoors in mid-winter in mild winter regions or plant seeds from late summer to late autumn for harvest the next spring.

Q: How can I blanch leeks?

A: The traditional way to blanch leeks is to set them in a 6-inch furrow and then gradually fill them in to blanch the stalks as the plants grow. This technique requires a lot of work and grit and soil can get into the folds in the stalks. An alternative is to wrap the leeks with brown paper or slip 6-inch tubes of cardboard or plastic (such as thin-walled, 2-inch, PVC pipe) over the stalks when they are almost an inch thick.

Q: Do I have to blanch leeks?

A: No. Leeks will be perfectly useable if you do not blanch the stalks. Blanching makes the stalks whiter and perhaps more succulent.

Q: When should I harvest leeks?

A: Leek varieties vary in maturity dates from 70 to 140 days. Leeks are edible at pencil-thin size or you can wait until they reach maturity when the stalks will be 1 to 2 inches in diameter. Don’t let them flower in the second year; they will be too tough to use in the kitchen.

Leek Varieties to Grow

  • ‘American Flag’ (90-120 days): classic, home garden variety; sweet flavor; 8 to 9 inches long, 1 inch in diameter.
  • ‘Bandit’ (100 days): thick, heavy, winter leeks for late harvest and overwintering.
  • ‘Carentan’ (90 days): green leaves and white shanks.
  • ‘Comanche’ (75 days): long, white shanks; dark-blue leaves; early fall harvest.
  • ‘De Carentan (110 days); long stems; sweet flavor; fine texture; grows rapidly; French variety.
  • ‘Elephant Leek’ (85 days): large stems; vigorous grower; widely grown.
  • ‘French Summer Kilma (75 days): dark blue-green leaves; long slender stems; European variety.
  • ‘Giant Musselburgh (105 days): Scottish heirloom, best winter hardy.
  • ‘King Richard’ (75 days): grows to full size in summer; not winter hardy.
  • ‘Lancelot’ (70 days): bolt resistant, virus tolerant.
  • ‘Large American Flag’ (130 days): thick stems; sweet flavor; widely grown.
  • ‘Lincoln’ (50-100 days): early variety with long, white shanks.
  • ‘Rally’ (85 days): heavy, uniform shanks; rust tolerant.
  • ‘Runner’ (100 days): thick, heavy shanks; blue-green leaves; winter leek.
  • ‘Tardorna’ (100 days): open-pollinated; medium-length shanks; fall-winter harvest.
  • ‘Tivi’ (75 days): long straight shaft; green tops; sweet flavor; Danish variety.
  • ‘Varna’ (60 days): quick-growing summer leek; good for baby leek.

About Leeks

  • The leek is a hardy biennial grown as an annual. It is a mild-flavored member of the onion family.
  • Leeks have thick white stalks topped with fanning, deed-green, strap-like leaves.
  • Left in the garden for a second season, leeks will flower and will not be flavorful.
  • Botanical name: Allium ampeloprasum Porrum Group
  • Family: Amaryllidaceae (onion family) — other alliums include onions, shallots, and scallions
  • Origin: Mediterranean, Egypt

More tips: How to Harvest and Store Leeks.

Grow 80 vegetables: KITCHEN GARDEN GROWERS’ GUIDE


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