Rising Leeks: How To Develop Beautiful, Luscious Alliums

Have you tried growing leeks? Luscious and delicious, they’re on every fine chef’s menu somewhere. In the UK, they’re a staple of the daily diet, and they appear heavily in Asian cuisine as well. Leeks are found in the most elegant dishes and at the finest restaurants.

You’ll find leeks growing in the finest of gardens, too. Their onion-like flavor is excellent for soups, roasts, risottos, stir fried, or in tarts. Harvesting leeks in summer, fall, and sometimes winter is a celebration. Planting leek seedlings that grow into fully-formed stalks packed with flavor is a reward in and of itself. 

Today, we look at the leek, explore some of the diversity of this allium, and learn the best way to cultivate these culinary delights. Leeks aren’t anywhere near as intimidating as they appear, and they’re well worth the time and effort spent growing them!

Leeks: Quick Care Guide

Homegrown American Flag leeks. Source: Lorin Nielsen

Common Name Leeks
Scientific Name Allium ampeloprasum
Days to Harvest 80-130 days
Light Partial to full sun
Water Consistently moist soil
Soil Nutritious, well-drained 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, onion maggots
Diseases Leek rust, downy mildew, powdery mildew, white-tip disease, botrytis leaf blight

All About Leeks

Crosscut leeksCrosscut leeks. Source: dbnunley

By now, you’re probably asking exactly what is a leek? The leek vegetable is a part of the allium species of the Liliaceae family. This is the same family of plants that encompasses onions, garlic, chives, and many others. Like the onion, a leek grows in layers. It is most similar to the green onion in that regard. Where do leeks grow? That’s also a common question. The leek has a long history.

Originally cultivated in central Asia, it spread throughout Europe due to its tasty nature. Eaten by the Egyptians and the Romans, it rapidly established footholds in most cuisines of Europe and northern Africa. Later, it came to the New World with the settlers, taking its place in the Americas. Delicious leeks have a subtler flavor than the onion and are often compared to scallions. However, they are milder than their more pungent relatives.

All leeks have shallow root systems and produce layers of green leaf masses from a slightly bulbous base. Like giant scallions, their slender stems grow through mild winters and are ready for harvest in spring. If they are left to bolt, they’ll produce a large globular flower, just as onions or garlic would. These are a great attractant for bees. 

Recommended Leek Varieties

Leek seedlingsLeek seedlings. Source: eakspeasy

Whether you choose to grow leeks from seed or via plugs, here are some of the best varieties of leeks to include in your garden this year. Can’t decide on which season to plant? Try the Autumn Giant variety, a midseason leek that takes roughly 100 to 120 days to mature. 

Early Season Leeks

  • King Richard: 75 days. Very popular. Light green slender shafts. Tolerates light bouts of freezing temperatures. King Richard leeks are a very popular variety!
  • Hannibal: 75 days. Thick stalks that are pure white, dark green leaves.
  • Roxton: 85 days. Uniform stalks. Does not bulb. Bright green leaves. It can be hard to find.
  • Varna: 80 days. Long, slender plants with shafts that are often harvested early for best flavor.
  • Megaton: 90 days. Bluish-green leaves. Thick leeks, very similar to late-season varieties.
  • Dawn Giant: 98 days. Gigantic leeks! Often used for competition.
  • Pandora: 90 days. Very uniform, non-bulbing. Bluish-green leaves. 
  • Runner: 105 days. Deep bluish-green leaves, very erect, easy to cultivate.
  • Striker: 86 days. Very easy to clean. Long, thick shaft. Disease-resistant.

Late Season Leeks

  • American Flag: 105 days. Grows extremely well. Frost-resistant strain.
  • Lancelot: 95 days. Reliable and classic variety. Rich green leaves.
  • Surfer: 115 days. Disease and pest-resistant variety with clean white stalks. Blue-green leaves.
  • Bandit: 100 days. Extremely cold-tolerant. Minimal bulbing.
  • Giant Musselburgh: 105 days. Very old variety. Super-thick stems and cold-tolerant.
  • Blue Solaise: 110 days. French variety, leaves are dark blue-green but turn purplish after a cold snap.
  • Carentan: 130 days. Old European variety that is quickly becoming rare. High yields, vigorous.
  • Jolant: 120 days. Winter-hardy variety with blue-green leaves and medium-sized stalks.
  • Tadorna: 110 days. Disease-resistant cultivar. Overwinters in all but the coldest locations.

How To Plant Leeks

Young leeks growingYoung leeks growing. Source: mrvklaw

Plant quicker-growing, early-season leeks in the early spring for harvest in the late summer or early fall. They’re often smaller than late-season species and even milder in flavor. Some people use these to grow mini-leeks that are used in food. 

Late-season leeks are also planted in spring, but they’re harvested in late fall and even into winter. These take longer to grow. They’re also cold-hardy and somewhat frost tolerant and handle gradual temperature changes. A few can be planted in the late spring for fall/winter harvest. Growing leeks in areas with mild winters is possible too. In this case, a fall planting is best for an early spring harvest.

Plant leeks outdoors anytime after the last spring frost date has passed. Start seeds indoors in late winter using a seedling heat mat and grow light. Direct sow leek seeds about four weeks before the final frost, and they will come up in the spring. Leek seeds don’t like deep plantings, and spring rains can wash the seed away. Use some sort of cover protecting your garden until the leeks have sprouted.

You can also grow leeks in containers. Space them out to allow their shallow root system to spread. Plant leeks in clusters of no more than 2 to 3 plants. Thin leek seedlings well after a thick direct seeding where they’re sown densely. You can germinate multiple plants in a single seedling starter tray. When you transplant seedlings, take those that produce clumps and gently separate their roots by swishing them in a bucket of water.

Make a 4 to 6-inch deep hole using a shovel handle or wide stick. Gently set young plants into it, making sure the leaf tips are above the soil level. Sprinkle a tiny dusting of soil around to cover the root. Don’t fill the hole in completely, as nature can handle that. Just be sure the roots themselves are covered. 

For lots of plants, use the trenching method. Make a long, deep trench in the ground or in raised beds. Place a leek in it and push enough soil to keep the seedlings upright, covering the roots. As the leek grows, push more soil around it to keep the stalk covered. Continue adding soil over time, keeping the stalk covered to promote blanching.

Caring for Leeks

Leek scapesLeek scapes. Source: kendura99

For the most part, after you transplant leeks, they can take care of themselves. However, if you want to have the most flavorful stalks, here’s the best way to ensure a tasty harvest.

Light and Temperature

Growing leeks in partial shade is ideal, but the leek will also handle full sun just fine. The stalk itself must be shielded from the bright sunlight so it blanches. While the ideal temperature is 60°F, and leeks prefer mild climates as a cool season crop, they’ll survive in warm climates too. If you grow leeks through a light frost, that’s ok. They can handle it. 

Most leek varieties tolerate heat as long as they have plenty of water. Long-growing, cool-season varieties are somewhat frost-tolerant too. In times when the ground freezes or when the soil temperature is very low, place a cloche or cold frame over the plants to keep them safe. Frozen ground can freeze leeks, and frozen leeks take on damage and are not edible. 

Water and Humidity

Growing leeks requires about an inch of water per week once they’re established. Leek seedlings need a bit more. While leeks grow poorly in soggy soil, keeping them consistently moist is ideal. Water leeks with soaker hoses for this purpose. You can also mound around the base of the plant with either soil or with mulch. This will help the soil around the roots stay moist. As long as you have well-draining soil, you can water leeks often, and in warm climates, you’ll want to do this.

Soil for Leeks

Plant leeks in nitrogen-rich, lightly-packed soil that has lots of organic matter. Well-drained soil is a must, and sandy soil full of nutrients is ideal. Before planting, loosen soil in your raised beds, containers, or garden ground, and work compost through it to a depth of about 12 inches. 

If you want to blanch the stalks naturally by starting them deeper, amend the soil to 12 inches beneath the lowest point you plan to plant each leek seedling. This ensures the transplant leeks have plenty of nutritious soil throughout the growing season.

Fertilizing Leeks

Leek seedlings and mature leeks are heavy feeders, but they don’t need much more through the growing season than compost-enriched soil. Work compost into the ground before planting. Growing leeks with some blood meal or bone meal also helps leeks thrive. If you want to use fertilizer, choose a slow-release balanced granular fertilizer or water-soluble plant food. You can also use a liquid fish emulsion or just add more compost occasionally.

Propagating Leeks

Leek bulbilsBulbils grow from the base of the parent leek. Source: Lorin Nielsen

Propagate leeks from seed or by bulbil. Leeks grow more reliably from seed. Follow the process to start seeds indoors in the Planting section, and you’ll grow leeks easily. Propagating by bulbils (sometimes referred to as pips) can be tricky. First, your leek needs to be producing bulbils along the stalk, which can be hard to identify while it’s in the ground. If you harvest a leek and find some, try to replant them!

Carefully separate the bulbils from the mother stalk, then tuck the base gently into soil to root it. As long as the bulbil’s shoot is green, you have a chance of growing leeks that are an exact clone of their parents. Re-plant leeks to encourage more offspring. If a plant generates a lot of bulbils, it may already be past the edible stage. A plant with only a few bulbils shouldn’t have noticeable flavor changes.

Pruning and Training Leeks

You don’t have to prune when you’re growing leeks unless you want to. Some varieties, such as American Flag, have edible greens which can be trimmed and used in cooking. If you have a variety that doesn’t have bitter greens, trim the first green leaf or two occasionally for kitchen use. Don’t take more than two or three leaves from a given leek during its growth cycle, though!

When you grow leeks, mound soil around the plants to cover the stalk up to the base of the leaves. This naturally blanches the stalk and encourages it to grow taller. Double your efforts by planting your leeks in a trench or hole initially, then gradually increase the amount of soil around the leeks.

Harvesting And Storing Leeks

A green-to-white rainbow of cut leeksA green-to-white rainbow of cut leeks. Source: sethoscope

After all that waiting through the growing season, you have a fine crop awaiting you! When to harvest leeks can be hard to decide, but let’s go over everything you’ll need to know.

Harvesting Leeks

Depending on the variety, harvest leeks at the end of the growing season anywhere between 60 and 120 days after sowing seed or after you start seeds indoors. Start when the stalk of your leek is about an inch across. You can harvest leeks (a summer leek, for instance) when they’re younger than that, but you won’t have as much produce, of course! 

As long as the soil is loose, grasp at the base of a leek and give it a good tug. This will free the roots from the soil but may damage the outermost leaf layer. If you’re harvesting from heavier clay soil or want to prevent damage, use a fork to loosen the soil around and beneath and dig leeks up. Shake or dust off as much soil as you can. Try to keep the roots intact unless you are going to use it immediately, as that helps it store longer.

Storing Leeks

You can store leeks incredibly well in the ground, so leave them in place until you need them. If you are going to overwinter leeks this way, hill up the soil around the plants and cover them with a thick layer of mulch to keep the base of the plant warm and store it in place. 

Leeks, like most other onions, can be stored outside the refrigerator as long as they are in a cool, dry place. Do not wash them until you are ready to use them. Instead, dust off any soil remnants and let the exterior dry. In optimal conditions, they store this way for up to three months. If you’re using your leeks soon, store them in the refrigerator. Trim off the excess greens and wrap each leek in plastic wrap, covering it completely. Place them in an airtight plastic bag and use them within two weeks. 

Leeks dry quite well in a dehydrator. To prepare leeks for dehydrating, slice them finely, and wash them so you have clean leeks. Put them in a dehydrator set at 145 degrees Fahrenheit until they are crisp. Store them in an airtight container out of direct light. If you’re storing for a longer period of time, add a moisture-absorbing packet to your leeks.

Troubleshooting

Leek harvestLeek harvest. Source: Muffet

While growing leeks isn’t hard, they do have some issues and plant diseases you need to be aware of. Let’s talk about those now. 

Growing Problems

One of the most common problems that occurs when you grow leeks is thin or spindly growth. The cause is overcrowding. Leeks are heavy feeders, and too many in one spot will cause them all to have problems! Thin out your leeks, especially when you scatter seeds in an area. When you’re planting seedlings, 6 inches apart is a good range to aim for. You might be able to grow them closer, but you may still find them to be too thin.

If you forget to thin them, and find that you have clumps of 2-3 growing together, fertilize and water leeks regularly. You can use a fish emulsion, kelp meal, or a thick layer of compost. I’ve also had success using organic fertilizer tea or compost tea. Some people deliberately grow this way to maximize their harvest in tight spaces.

While we love to see other kinds of flowers, a lot of people dread seeing their leek flower. Flowering renders the stalk woody and causes it to go bitter and inedible. Most leek flowering comes from sudden shifts in the weather. When the weather goes cold, put a cold frame over your growing leeks before they get too chilled. Gradually acclimate them to the new conditions.

If the leek does send up a flower stalk, harvest it before it blooms. Congratulations, you now have what’s called a leek scape! Use it in cooking for a mild flavor. If you catch the scape while it’s still small, your leek will not suffer, and you’ll still be able to harvest and use it too.

Pests

In the UK, the leek moth and its larvae are a concern for those who grow leeks. Tiny caterpillars tunnel into the leaf stalk to feed, causing brownish patches. Older caterpillars tunnel down the center of the stalk, causing rotting or withering. After a month or so, the caterpillar pupates. Bacillus thuringiensis, known as Bt spray, wipes them out. Remove and destroy affected plants. Hand-pick larvae and prevent moths by using floating row covers.

Thrips are small bugs that can be controlled by releasing beneficial insects such as ladybugs and lacewings into your garden. Keep the area near your leeks clear of plant debris and grass, which is a home for the thrips! If your leek patch has a severe infestation of thrips, use neem oil to deter them. Insecticidal soap will also work in a similar fashion. Finally, pyrethrin-based sprays will kill thrips if nothing else works.

The onion maggot is among fly species that affect onions, but it affects leeks too. The adult flies lay their eggs on the soil surface, which hatch. Then larvae tunnel into the earth and feed on the bulbous areas of alliums. Young plants are most susceptible to maggot damage. There is no cure for them, so use floating row covers, and rotate your allium crops regularly.  

Diseases

Leek rust is a fungal infection that looks like orange pustules on the leaves. If you discover rust on your leek, know it is generally just a cosmetic issue. Simply remove any rust patches you discover and destroy them. To prevent rust, rotate your crops regularly so the fungus can’t take hold. You can also use a liquid copper fungicide to control rust when it appears.

Powdery mildew and downy mildew aren’t common on leeks but do happen, especially if nearby plants are suffering from it. Remove damaged leaves, and remove plants if they are overcrowded. Most of the time, you can still get a harvest from leeks with mildew, but ensure it hasn’t gotten to the area you’re eating before you use them.

Botrytis leaf blight is caused by Botrytis allii, a fungus that causes mold between layers, a breakdown of the bulbous area of your leeks. This disease is more prevalent in areas where leeks aren’t properly spaced and the soil is overly moist. Prevent these conditions to prevent the disease. Unless you’re willing to use systemic fungicides on your crops, there is no treatment. 

Purple blotch is a fungal disease caused by Alternaria porri. This disease causes water-soaked lesions on more mature leaves that are either purple or brown, with a yellow ring. The rings then develop into a bull’s eye pattern. Keep your garden free of plant debris to prevent the spread of this disease. Good air circulation and proper watering prevents the disease as well. Thrips also spread the disease. Use prevention methods to keep this disease at bay. 

White tip or white rot disease, also referred to as white tip of leek, is a fungal infection. It usually results from infected soil splashing up onto the leaves and can also impact onions. While it’s far more common in the UK than elsewhere, it’s not entirely unknown in the United States. You’ll need a chlorothalonil fungicide to repair plants suffering from white tip.

Finally, pink root is a disease that causes pinkening of root masses, which eventually turn brown and die. Usually, this disease – which eventually causes dieback of the entire plant – is prevalent when leeks are planted late. Try to plant early so most of the plant’s growth occurs early in the season before the fungus can attack. Rotate your crops and plant resistant varieties. 

Frequently Asked Questions

Pale leek flowerPale leek flower. Source: safoocat

Q: I heard you could grow leeks from kitchen scraps?

A: You can if the leek has roots still on it. Cut off the bottom of the stem, leaving at least an inch to an inch and a half of the base. Place the root end in a cup of water, and put the cup in a sunny window. Rinse off the end of the leek and change the water daily. Within a week or so, green shoots will form. At that point, you can plant the leek in potting mix and let it grow! Many types of plants can regrow from kitchen scraps.

Q: Are there perennial leeks as well as annual leeks?

A: Yes! Perennial leeks actively form new bulbils much in the same way that a shallot does. Annuals may form bulbils, but only when the parent plant is past its prime and ready to go to seed. The flavor of perennials is more oniony than an annual. The majority of commercially available leeks are annual varieties.

Q: What is the best month to plant leeks?

A: Depending on where you live, the growing season either begins in spring or fall. Plant and grow leeks in March, April, September, or October. 

Q: How long does it take to grow leeks?

A: Leeks take anywhere from 80 to 130 days to mature.

Q: Do leeks grow back every year?

A: Perennial varieties in the right conditions do, yes. 

Q: Do leeks regrow after cutting?

A: They do as long as only their first couple of outer leaves are harvested. Make sure you have a variety that has flavorful leaves before you use them in food.

Q: Can you leave leeks in the ground over winter?

A: Yes, as long as you grow leeks in an area where winters aren’t harsh, you can overwinter and continue growing leeks in the next growing season. 

Q: Can I grow leeks in pots?

A: Growing leeks in containers is entirely possible, but ensure you have enough spacing between plants for maximum harvests.

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