Harvesting Leek Plants: Tips On When And How To Harvest Leeks

Harvesting Leek Plants: Tips On When And How To Harvest Leeks

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By: Jackie Carroll

Leeks are members of the onion family, but instead of forming a bulb, they form a long shank. The French sometimes refer to this nutritious vegetable as the poor man’s asparagus. Leeks are rich in vitamins C, A, and folate, and they also contain kaempferol, a phytochemical believed to help prevent cancer. Let’s learn more about picking leek plants in the garden to take advantage of all they have to offer.

When to Harvest Leeks

Most leeks mature 100 to 120 days after sowing the seeds, but a few varieties mature in as few as 60 days. Begin the harvest when the stalks are about an inch (2.5 cm.) across. Depending upon your climate, you could be harvesting leek plants from late summer until early spring. Picking leek plants that mature at different times of the year lets you extend the harvest.

Leeks are best used fresh, but if you must store them, wrap them in a damp paper towel and place them in a plastic bag in the refrigerator for seven to 10 days. Smaller leeks keep longest, so use the large ones first. Don’t trim them until you are ready to use them.

How to Harvest Leeks

Harvest leeks from loose soil by pulling them up. Pulling them out of heavy soil can injure the roots. Use a garden fork to reach under the roots and lift them from heavy clay soil. Shake the plants and brush off as much soil as possible and then rinse them thoroughly. Slice leeks in half lengthwise immediately before use and rinse out any remaining soil.

Begin the garden leek harvest early by cutting a few of the leaves before the plant is ready to harvest. Use a sharp knife to cut the leaves from the plant. Harvesting too many leaves stunts the plants, so take just a few leaves from each one.

Leeks have a limited storage life, but you can overwinter part of the crop in the garden. As winter weather approaches, hill up the soil around the plants and cover them with a thick layer of mulch. Use this method to extend the harvest and enjoy fresh leeks well into winter. Some varieties overwinter better than others. Look for varieties such as ‘King Richard’ and ‘Tadorna Blue’, which are bred for overwintering.

Now that you know when and how to harvest leeks in the garden, you can enjoy the benefits of a healthy lifestyle.

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Leeks in the Garden

Leek is a hardy cool-season biennial that prefers full sun and fertile, well-drained soils. Incorporate plenty of organic matter and a complete fertilizer into the area before planting. Plant seeds Вј-ВЅ inch deep, 3-4 inches apart in the row, and 8-16 inches between rows. Side dress leeks with nitrogen in May and June to ensure good growth and high yields. Leeks require regular watering, so maintain soils near field capacity. Water stress will reduce yields and plant size. Organic mulches help conserve water, supply extra nutrients and reduce weeding. Control weeds, insects and diseases throughout the year. Leeks may be harvested and used when larger than one inch in diameter. In more mild areas of Utah, leeks can be stored in the garden by hilling up the soil around the plants and covering them with mulch. In very cold areas, harvest the plants and store in cold (32-40F), humid conditions to maintain best quality. Excellent varieties include Large American Flag and King Richard.

Leeks: Quick Care Guide

Common Name Leek, wild leek, broadleaf wild leek, King Richard leek, Hannibal leek, Roxton leek, Varna leek, Megaton leek, Dawn Giant leek, Pandora leek, Runner leek, Striker leek, American Flag leek, Lancelot leek, Surfer leek, Bandit leek, Giant Musselburgh leek, Blue Solaise leek, Carentan leek, Jolant leek, Tadorna leek, and many others
Scientific Name Allium ampeloprasum and related cultivars
Germination Time Variety-dependant, generally 8-16 days
Days to Harvest Variety dependant, 80-130 days
Light Partial to full sun
Water Regular watering, moist soil
Temperature 60 degrees Fahrenheit is optimal
Humidity Humidity okay but not required
Soil Light to hard-packed soil, nitrogen-rich
Fertilizer Compost-amended soil. Can also use fish emulsions or kelp-based liquid fertilizers or a slow-release granular fertilizer.
Pests Leek moth, thrips
Diseases Rust, powdery mildew, white-tip disease

1. Leeks

As part of the onion family, leeks are vegetables that are easy to cut and come again. If you are growing leeks outside, just cut the plant above the root end and new growth will appear on top. You can also save the ends of the plants and grow them in soil. The roots will take hold and produce new growth at the top, allowing you to double your leek harvest!

If you are looking for leek seeds, you might be interested in trying these wild ramp seeds. Similar to leeks, they have become very popular in recent years. I also do a lot of shopping from the Green Witch Seed Co. since they offer tons of heirloom varieties and all non-gmo options.

Growing Leeks

In November and December, between harvesting trips to the garden, leek growers are deciding which varieties to grow next year. Leeks ( Allium porrum or A. ampeloprasum porrum ) are the easiest to grow of all the alliums. Not only do they perform well in a wide range of climates, they can be harvested at almost any stage for use raw as baby leeks in salads or cooked in soups and sautees.

Their complex onion flavor, though sweet and sharp, is mild enough to be a refreshing relief to breath-conscious diners. They're rarely troubled by pests and diseases and are not finicky about soil fertility and transplanting. And in the garden, they're attractive: Some varieties have blue leaves that contrast strikingly with white stalks, and a few have foliage that deepens to violet after frosts.

Leeks are biennial plants, meaning they're programmed to germinate and grow one season, survive the winter, and then flower and scatter seeds the next season. Most varieties (except those grown for baby leeks) need about 10 to 12 weeks from sowing to reach transplant size, then 12 to 20 weeks in the garden to reach harvest size, depending on the variety and when you wish to use them in the kitchen. You can harvest frost-susceptible varieties in the summer and fall, or leave mulched, frost-tolerant varieties in the garden for winter-long harvests.

Leeks Prefer Cool Weather

They grow best when temperatures are between 55° and 75° F growth slows at temperatures above 77° F. Some varieties tolerate cold down to 22° to 24° F with no ill effects, and a few even survive temperatures below 0° F if mulched with 12 or more inches of straw. Leeks prefer fertile soil that isn't compacted or poorly drained. Like onions, they don't grow well in soils with little organic matter or in soils that are overly acidic. But the ideal leek soil is the same as for many vegetables-loose, well drained, nutrient- and humus-rich, and with a pH of 6.5.

When to Sow

In northern gardens, the standard and most reliable planting sequence for leeks begins with sowing seeds indoors 12 to 14 weeks before the last frost in your area. Then seedlings are ready to transplant 2 weeks before the last frost. For instance, if you live in Ithaca, New York, or North Platte, Nebraska, where the last frost in spring is usually in the middle of May, sow seeds indoors in mid-February. After 10 to 12 weeks (mid- to late-April), the seedlings should be about the diameter of a pencil and ready to transplant outside.

If you live where the autumns are long and cool and frost is rare (such as in USDA Hardiness Zones 8 through 9a), you can plant two crops. Sow the first crop 12 to 14 weeks before the last frost in spring. In mid-July, sow the second crop indoors. If your area could experience frost during the winter, plant a frost-tolerant variety. After germination in summer, keep seedlings in a cool but bright location until they reach transplant size in late September or early October. Then transplant them outdoors and grow and harvest them through the late fall and winter.

Because leeks prefer cool weather, if you live in zones 9b to 11 where the summers are scorching hot and the winters are mild, sow seeds (indoors) only in July or August to harvest through the late fall and winter. Or harvest after winter in spring if you plant a bolt-resistant variety.

Sow seeds 1/4 to 1/2 inch deep in a lightweight soil mix in flats. If you start leeks in the summer, chill the seeds overnight in the refrigerator before planting. The optimum soil temperature for germination is 52° to 73° F. The seeds should germinate in one or two weeks. Immediately after germination in late winter or early spring, set seedlings on a bright, south- or west-facing window sill, or under fluorescent grow lights. In 10 weeks or so, transplant them.

Set pencil-thick transplants 4 to 6 inches apart in rows that are 12 to 18 inches apart. More space per plant results in fatter leeks, and less space produces thinner ones. Use a dibble or broom handle to make holes that are 6 inches deep, and place one transplant in each hole. Water them in to settle soil around the roots, but don't fill the holes with soil. Let that happen naturally over the season. Planting leeks deep in soil blanches them, shielding the shanks (the portions below the point where the leaves fan out) from the sun and keeping them white, tender, and sweet. Leeks are palatable without blanching, but blanched shanks have better flavor.

A week after transplanting and again halfway through their growing season, give the leeks a nitrogen boost with manure tea or fish emulsion. Throughout the growing season, keep plants well watered. Also keep leeks weed-free, because as with onions, fast-growing weeds stunt the growth of young leeks. Get the weeds when they're small, and you'll avoid damaging the shallow-rooted leeks in the process of uprooting large weeds.


Leeks are ready to harvest whenever they are large enough for your taste. Most leeks can be harvested for use as baby leeks, but some varieties are bred for culinary appeal as baby leeks. In addition, like carrots, frost-tolerant leek varieties taste better after a few frosts.

To avoid damaging the edible portions, use a garden fork to loosen the soil around the leeks first. Stick the fork into the ground parallel and next to the row, and pull down on the handle, forcing the soil to release the leeks. Leave most of the roots intact, and cut the top leaves off in a V shape, with the outside leaves the shortest this not only neatens their appearance, it slows transpiration that causes limp leeks in the kitchen as well.

If you want to keep leeks through damaging cold periods, harvest and store them in a root cellar. Arrange leeks neck-to-neck, upright, in boxes or crates. Pack moist sand or mulch tightly around the bases. They should last for two to six weeks.

Varieties of Leeks

Though all leeks tolerate some frost, some overwinter better than others. Here's a guide to help you decide. Try several varieties in a small garden-the seeds store well for three years if kept cool and dry. In the list, the days to maturity are from transplanting, except where noted.

Good varieties for frost-free regions:

'Otina' (120 days). Long, thick early leeks from France flavor delicate enough to be eaten raw in salads. Blue-green foliage.

'Titan' (70 days). Dark green leaves. Good for summer and fall harvesting. Very long stalks, early growth, and dark green foliage.

'Varna' (50 to 85 days). Fast-growing, slender, and tall variety grown (often in bunching crops) for baby leeks. Light green leaves.

Good varieties for mild-winter regions: 'Albinstar' (110 days from sowing). Dutch seedsmen developed this one especially for use as baby leeks, so harvest these when they're about 1/2 inch thick for baby leeks, or grow to full size. Deep green leaves.

'Electra' (150 days). Good for summer and fall harvests, but can be overwintered with protection. Dark blue-green foliage and long white stalks.

'King Richard' (75 days). Bolt-resistant. Market gardeners often grow this variety for baby leeks because of fast growth. Tender, tall, and slender stems. Light-green leaves.

'Pancho' (80 days). An early leek that's good for summer and fall harvests. Short, thick stems with deep blue-green foliage.

'Parton' (85 days). The only F1 hybrid leek and new to North America this year. Yields are purportedly 35 percent higher than those of open-pollinated varieties. Long and fast-growing with green leaves.

'Splendid' (95 to 105 days). From Denmark. Long, slender stalks and green foliage.

'Tadorna' (100 days). Medium length, white shaft contrasts sharply with very dark blue-green leaves.

Good varieties for cold-winter regions: 'Arkansas' (108 to 120 days). Bolt-resistant. Dark, blue-green leaves.

'Bleu de Solaise' (105 days). This French heirloom can be overwintered in short-season areas. Leaves are large and blue.

'Durabel' (125 days). Bred to handle winter weather, this Danish variety has milder flavor for use raw and more tender texture than some winter-hardy leeks. Bolt-resistant.

'Giant Musselburgh' (110 days). Popular, large heirloom that also does well in the South. Bolt-resistant. Green fan-shaped leaves.

'Large American Flag' (same as 'American Flag', or 'Broad London') (130 to 140 days). Popular home garden variety producing fat leeks with broad green leaves.

'Laura' (115 days). Extra hardy for fall harvest and overwintering. Dark green leaves on medium-length stalk.

'Longina' (140 days). Adapted to a variety of growing conditions. Long, thick stems and deep blue-green foliage.

'St. Victor' (145 days). New strain selected from 'Bleu de Solaise'. Stores well in the ground, and foliage turns to deep violet as cold increases.

'Winter Giant' (same as 'Alaska') (115 days). With broad, blue-green foliage, a stocky, bolt-resistant heirloom.

Kathryn Khosla is a university horticulture graduate, and at the time of this article, lived in central New York.

Photography by National Gardening Association and Charlie Nardozzi/National Gardening Association

Garden Variety: Some tips on growing and harvesting leeks

Jennifer Smith

When many crops in Kansas vegetable gardens are nearing the end of their season, leeks are just coming into their own. Gardeners and farmers who planted them last spring may begin harvest in September to early October depending on the planting and maturity dates for the variety they are growing. With careful planning, selection, and a little extra care, harvest may continue throughout the winter.

Leeks are related to onions, garlic, shallots, and other alliums and grow in a similar fashion. At the base of the plant is a bundle of leaf sheaths that look like a small white onion. The white bulb-like structure is topped by long, slender, dark green leaves. Leeks are sold with leaves intact and much of the leaves may be used in cooking along with the white base.

Cooks use leeks raw in salads or cooked as a flavoring for soups and stews, stir-fry, Turkish and Welsh cuisine, and other dishes. They are often described as having a mild onion-like flavor. Purchasing fresh, local leeks while they are in season is the best way to try them at their peak of freshness and flavor.

To add leeks to the garden next year, plan to plant them in spring. If starting from seed, plant the seeds in trays indoors a couple of months before they will be moved outdoors. Purchasing seedlings may be easier although harder to find. Consider purchasing leek plants online or by mail order if they are unavailable locally. Plant in full sun in any type of garden with well-drained fertile soil. Leeks can even be grown in tall containers.

To get the white base on leeks, the base must be completely hidden from the sun. Plant leeks six to eight inches deep and about 6 inches apart to give them room to grow. If the plants are too short to plant at that depth at the time of transplanting, dig the hole to that depth, but only fill it in enough to support the plant. As the plant gains height, the hole can be filled in to ground level.

Mulch plants after transplanting to reduce weed competition and reduce soil and moisture fluctuations. Straw or prairie hay are typically preferred in vegetable gardens, but any sort of mulch is better than leaving bare soil around the plants.

When stems are about an inch thick, mound soil and/or mulch up on the stems to create even more depth.

Harvest begins when leeks have reached the size of your liking. Harvest a few at a time and/or as the leeks needed since they will continue to grow very slowly when left in the ground. Use a spading fork or shovel to loosen the soil around the plant and lift them out of the deep soil. Trim the roots and tops, wash, and they are ready to use.

Leeks are generally considered hardy to USDA Hardiness Zone 7. Lawrence is in Zone 6, meaning it is a little colder. In a mild winter, leeks can be harvested all season. But in a very cold winter or in a period of cold weather extremes, leeks may freeze in the ground. If very cold weather is expected, harvest any remaining leeks to avoid them freezing.

Adding an extra deep layer of mulch around the plants as winter approaches can also help them to survive especially cold temperatures.

Research varieties when selecting which leeks to grow. A few varieties have a short maturity date and may be ready to harvest in the summer after a spring planting. The best varieties for fall and winter harvest will be labeled as such or are sometimes. They typically have maturity dates of 100 to 120 days after planting.

Leeks can be interplanted with other crops to save space in a vegetable garden, or incorporated into the landscape as their foliage is attractive.

— Jennifer Smith is a former horticulture extension agent for K-State Research and Extension and horticulturist for Lawrence Parks and Recreation.

Leek Varieties Worth Growing

Judging by appearance alone, one might suspect there’s one kind of leek to grow. The tall, thick, green-leaved, white-stemmed kind.

However, you’ll find there are many varieties worth growing. Planting more than one variety also helps you spread out your garden harvest, so you can eat fresh leeks for several months in the year.

  • King Richard (75 days to maturity)
  • Lincoln (90 days to maturity)
  • Tadorna (100 days to maturity)
  • Giant Musselburgh (105 days to maturity)
  • Bleu de Solaize (105 days to maturity)

Within these leek varieties, some are considered fall leeks, the rest, winter-hardy ones. Imagine if you could harvest fresh leeks from October through February.

Give them a try, I think you’ll find leeks to be an easy to grow addition to your garden.

Why not mix it up and plant some of each? Then convince another gardener to grow leeks too.

Watch the video: Vegetable Seed Saving - Leek and Onion!