How to Grow Leeks: The Complete Guide (2024)

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Leeks like full sun, doing best with at least 8 hours a day, if they can get it. They need deep, fertile, well-drained soil with high organic matter levels. A soil pH of 6.0-7.0 isideal.

When to PlantLeeks

• Leeks can be bought from a garden center or greenhouse as young plants or started from seed easily at home. They are cool weather tolerant and can be planted out before your last frost.
• If starting from seed indoors, you’ll want to get them sown about 8-10 weeks before your last frostdate.
• If transplanting your own or purchased seedlings, harden them off for several days and then plant them out 1-3 weeks before your last frost, when temperatures reach 45 degrees Fahrenheit (7°C) during the day. Leek seedlings can tolerate a light frost, and can be planted out several weeks earlier than mostplants.

How to PlantLeeks

Starting leeks from seed at home is inexpensive and easier than you might suspect. While prices vary widely with variety and organic certification, you can purchase 250 leek seeds for as little as a five-dollar bill. Look out for varieties described as ‘rust resistant’, as this fungal disease can cause minor problems from summeronwards.

Leeks can be planted in the in-ground in your garden, in raised beds, or even in deep containers. (Read about the benefits of each method.)

To start leeks fromseed:

• Sow them in soil blocks or prepared trays of well-moistened seed startingmix.
• Plant the seeds about ¼ inchdeep.
• If planting in cell trays, drop two seeds per cell and thin to one per cell if necessary once they havegerminated.
• Keep them moist but not soggy, and provide plenty of light once theysprout.

Once your leeks are ready to plant out, follow thesesteps:

• Leeks like organic matter. If needed, gently work several inches of compost into the plantingbed.
• Leek seedlings should be planted deeply to encourage long stalks. They can be grown in two methods: trenching or hilling. Check this page from the University of Wisconsin Extension for more information on how to plant leeks.
• For trenching, dig a trench 6 inches deep. Plant your leek seedlings in the bottom and water in. Don’t fill in the trench yet. You’ll do thatlater.
• Leave enough space between plants for goodairflow.
• For hilling, plant your leeks as other plants, and water in. Later, you can hill them likepotatoes.
• Mulch your leeks to keep the soil near the surface from drying out and reduceweeds.

Whether you grew them from seed or bought transplants, caring for leeks is the same and is prettystraightforward.

• Leeks have shallow root systems and will need regular watering. Irrigation provided at the soil level creates fewer problems than overhead sprinkling. Drip irrigation is ideal for running under your mulch and provides water right at the roots where your leeks needit.
• About an inch per week is sufficient, however, monitor the soil. If the top 2-3 inches are dry, give them a drink. Leeks planted in sandy soil will need morewater.
• As your leeks grow, either fill in the trench or hill the soil. 2-3 times over the beginning of the season will be sufficient. The soil around the stem will provide a blanching effect, making the white portion longer andsweeter.
• Mulch around your leeks to keep weeds down and encourage healthy soilconditions.
• Take it easy with the cultivator. The shallow leek roots can be easily damaged by cultivation or hoeing. Use mulch and hand pulling to keep the weeds incheck.

Visit Cornell University’s Growing Guide for more tips on growing leeks.

• ‘Tadorna’ is a vigorous grower with dark green-blue foliage that will overwinter in mildclimates.
• ‘King Richard’ is a large leek with shanks that may reach a foot long. It will tolerate fall temperatures down to 20 degrees with minor damage. An early-maturing leek at 75 days, it is an excellent choice for northerngardeners.
• ‘Dawn Giant’ lives up to its name, with a 15-inch shank reaching 2 inches in diameter.
  

Leeks will be perfectly happy to sit in your garden and do their thing. Unlike some other crops, which must be harvested all at once and stored, you can go snag half a dozen leeks whenever you need them from late summer until the groundfreezes.

• If you live in warmer climates, usually USDA zone 7 or above, you can likely keep them in the ground all winter. As long as the ground doesn’t freeze, store your leeks in their gardenbed.
• Leeks can be harvested early—a great way to thin them—or left to grow larger than an inch indiameter.
• Young leeks harvested at finger size will be more mild and tender and are great for eating fresh in salads or pestos. Larger leeks develop more flavor andtexture.
• The tops won’t die back like an onion, and in fact, in more temperate areas, leeks will display their biennial nature and bloom the second year like a carrot.

Andy Wilcox