Growing Leeks

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growing leeks in the garden

ripe leek with white lower stem

Ideally, leek stems will be long and white at harvest time. The white part is where the stem was blanched underground, hidden from sunlight.

Grace your dinner table with an easy-to-grow, elegant onion cousin: the leek. Sweet and mild, leeks are gentle on the digestive system and play the role of onion in dishes, only toned down. Unlike onions, leeks don’t produce bulbs, but stash their flavor in thick, juicy stems that look similar to giant scallions. Leafy stems are pretty, and growing leeks doesn’t require much room in the garden.

In the supermarket, leeks cost a premium; harvested from the garden, they’re a bargain. Leeks are most famous for leek and potato soup, but they’re also good steamed like asparagus, oven-roasted, chopped in quiche, or wrapped in ham and baked (perhaps with a little cheese on top).

Frost-tolerant leeks thrive in cool weather. In zones 7 and warmer, plants can overwinter in the ground, making them perfect for fall planting. In northerly zones, tuck plants into beds in early spring, as soon as soil can be worked.

Soil, Planting, and Care

Separate the leek seedlings to plant each individually in the garden.

Remove leek seedlings from their Bonnie pot and gently coax them apart, then plant separately.

Plant leeks in a sunny spot in soil that is fertile and well-drained. Leeks thrive in traditional garden beds, raised beds, or even in tall containers, so choose whatever works best for you. Space leeks 6 inches apart when planting.

Leeks need two things to thrive: lots of nitrogen and consistent soil moisture. If possible, add compost or organic fertilizer to the leek bed the season prior to planting. Otherwise, work make a point to work organic matter into the ground a few days before planting.

To produce a succulent white stem, leeks must be blanched — in other words, covered or hidden from the sun. To do this, plant leeks into deep holes. (Deeper planting yields a more drought-resistant plant, too.) Create a narrow trench 6 to 8 inches deep, then tuck seedlings into the trench, adding soil back so it comes up to the base of the first green leaf. Water well.

Leek seedlings should be planted deeply up to the point where the leaves separate.

Bury the plants up to the point where the foliage arises from the stem, but not so deep that soil gets into the folds between the leaves.

After planting, mulch the bed with straw or some other organic material to help soil retain moisture. Soak newly planted leeks with a liquid fertilizer such as Bonnie Herb & Vegetable Plant Food. Water leeks as needed until plants are established. After that, plants require an inch of water a week, either through rainfall or irrigation. Inconsistent moisture yields tough stems. Continue fertilizing plants with liquid plant food every week or so during the growing season.

As leeks grow, mound the soil from the trench around stems, beginning when stems are 1 inch thick.

Troubleshooting

Leeks and kale grow in the snow in the garden. They are two of the most cold hardy vegetable plants.

Leeks are cold-hardy down to about 5 degrees. Northern gardeners often “store” their leeks in the ground through winter (snow acts as an insulator), pulling them as needed.

Soil that tumbles into leaf folds can wind up trapped between skin layers in the stem. To keep this from happening you can slip a section of paper tube, such as from toilet tissue or paper towels, over the plants while they are still young as early as planting time. The tube will rot over the growing season, but will help prevent soil from getting into leaf bases during early growth.

On young plants, slugs can be devastating. Gather them at night, set traps, or use biological control. If there is a lot of rain in winter or early spring, leaf rot can set in. Rot shows as white spots on leaf tips that eventually shrivel. At this point there is not much you can do except pull the rotted plants and thin the planting to increase air circulation.

In summer, orange pustules on leaves indicate leek rust, which is worse in wet growing seasons. Remove affected foliage; later maturing foliage will be healthy.

Because they are so cold-hardy, you could find that you still have leeks left in the garden that have made it though the winter, planted many months before. At this point, dig them because they will throw up a bloom stalk that ruins the fleshy texture of the stem.

Harvest and Storage

Leeks growing in a garden have long leaves. They are members of the onion family.

Leeks are members of the onion family with long, cold-hardy, strap-like leaves.

You can start pulling leeks from the ground just about anytime. Typically, you’d let them get least 1 inch or larger in diameter for the big white stems, but you can dig young ones to eat like scallions. If the soil is moist, they may just pull right out of the ground. If they resist, use a spading fork to loosen soil and then gently pull leeks by grabbing them at their base.

In zones 7 and warmer, you should be able to harvest leeks all winter long.

In colder areas, extend the harvest season by mulching deeply around plants (up to 1 foot deep) before a hard freeze. You could continue harvesting leeks until they are locked frozen into the ground, but don’t let that happen. Dig them first and store.

Wash the stems thoroughly to remove soil and grit that may have collected between the leaves.

For short-term storage (up to one week), tuck stems into an airtight plastic bag and place in the refrigerator crisper. For longer storage in coldest zones, dig leeks with roots attached. Cut leaves back until just an inch of green remains on each leaf. Place stems in a box (root side down) and pack with sawdust, clean sand, or vermiculite. Keep the packing moist and store in a cool place. Stems will keep up to 8 weeks.

To freeze leeks, wash, slice, and blanch for 1 minute in boiling water. Drain, drip dry, and toss into plastic freezer bags. Add the frozen leeks to soups, stews, and other dishes.

FAQs

Should I just plant the pot of leeks like I do with other Bonnie plants?

No, this is an exception to our plant-the-pot rule. Our pots are sown thickly with leek seedlings, which means you get a lot in one pot. Gently separate the seedlings to plant.

Will leeks grow in pots?

Yes, you can grow them in containers. Use a container about 18 inches deep and fill it only about 2/3 full of soil to begin with. Continue filling as the stems grow so that they will blanch. Make sure to water and fertilize regularly. Use a liquid plant food when you water to encourage fast growth that will result in tender stems.

Just how cold hardy are leeks?

American Flag, the heirloom variety that we offer, is one of the most cold hardy. You will also run into what is called a “summer leek” which is intended to plant in spring and harvest before cold weather. However, American flag will over winter in Zones 7 and warmer, easily tolerating temperature in the teens.

If I don’t blanch my leeks are they still edible?

You can strip away the leaves and eat what white part of the stems is left below the leaves. The green portions are actually edible, but they won’t be as tender.

21 thoughts on “Growing Leeks

  1. We just purchased a pot of Bonnie Leeks. We have never grown them before. Is there a way to store leeks for winter use?

    • Hi Luwanda,
      There sure is. Pull down the harvest and storage tab on this page for details on short term and long term storage. – Danielle, Bonnie Plants

    • Christine, I would use a container at least 10 – 12 inches deep. – Danielle, Bonnie Plants

  2. Just purchased Bonnie plants, leeks among them. I was wondering what variety of leeks they are as the identifier tag only say “leeks”

    Thanks

    Jim

    • Hi Jim,
      A member of the onion family, leeks are often called the gourmet’s onion because of their mild flavor. This version, called American Flag, is one of the favorite leeks for home gardens. – Danielle, Bonnie Plants

  3. Hi I just planted leeks today. Is it a bad thing that I planted the whole pot instead of separating the seedlings?

    • Alexis,
      That is not a bad thing, but you may not get the size leeks that you want. Bonnie Plants leek pots are sown thickly with leek seedlings, which means you get a lot in one pot. Gently separate the seedlings to plant. – Danielle, Bonnie Plants

  4. Haley wanted to know how to mound the soil. Haley, to mound the soil. you push or pull the surrounding soil up around the plant to cover it up. Just like when you plant potatoes, as the potatoes are growing under the soil, they push the ground up and need to be mounded, that is to put more soil on top of the plant so they don’t don’t get sunburned. so……mound up your leeks with the surrounding soil to keep the sun from making the leaves green.

  5. Hi there, I live in Las Vegas and have some American Flag Leek seeds. Should I wait until fall to plant (of course starting seedlings inside for the required amount of time) or can I start plants for spring planting (and if so, do they also need to be started inside or can I put the seeds directly into the ground since the ground is warm (temperatures are about 70 degrees during the day and about 45 at night). Thank you for your time :)

    • Hi Rene,
      I thought you may find this publication from the University of Nevada Cooperative Extension pretty handy. This is your local guide to planting cool season crops in your area. And, since you mentioned Fall, this is your fall gardening checklist.
      Happy Gardening,
      Danielle

  6. I planted leeks last spring but didn’t harvest them before the frost. We had a warmer than normal winter. Only a few weeks with near 0 temperatures. Some still have green stalks, will these leeks still be OK?

    • Hi Karen,
      Many of the onion plants are very persistent in the cold weather. Yes, you can harvest those leeks. However, you may find that parts of the leek will be very woody. I would harvest and see.

      -Danielle

  7. I PUT MY LEEKS IN LAST , APRIL, MAY BUT THEY HAVE NOT GROWN. CAN I MOUND THE SOIL UP AROUND THEM OR HAVE I LEFT IT TOO LATE . I PULLED ONE UP AND THE WHITE PART THAT GROWS UNDER THE SOIL WAS ONLY 5 CM LONG AND THAT WAS ONE OF THE BIGGEST.

    THANKS
    RACHEL

    • Hi Rachel,
      Let’s see how you spaced the leeks when you planted, as they may indicate their mature size. As you can see in the article above, “Space leeks depending on the stem size you want to harvest. For thickest stems, space seedlings 6 to 8 inches apart. For thinner, scallion-size leeks, follow tighter spacing, setting seedlings 3 to 4 inches apart. You’ll gain the best of both worlds by spacing seedlings 3 to 4 inches apart and thinning every other stem when they reach scallion size, allowing remaining stems to grow to thicker size.” Are yours crowded together or spaced well enough apart? ~Mary Beth, Bonnie Plants

  8. Is it too late to seperate leeks when you’ve put them in the ground if it’s just been a few days?

    • Hi David,
      I think that it will be fine to do so. Make sure to fork up the soil from underneath rather than pulling leeks up by the top. You’ll want to be gentle with roots. ~Mary Beth, Bonnie Plants

  9. I live in Auburn, Alabama and want to grow leeks for my fall/winter garden. Can I buy the plants directly from you? I would like to put them in the ground the beginning of September.

    • Hi Nanette,

      You should be able to find our plants in your area this fall. If you don’t already have a favorite Bonnie retailer, you can use our plant finder to locate one nearby. Happy growing!

      Kelly, Bonnie Plants

  10. I had a quick question about the last paragraph about mounding the soil. What exactly do you mean by hat and what would its purpose be? Also, when would you know when to harvest leeks? Thank you. Mine are about 3/4″ in diameter.

    • Hi Hayley,

      If you look a couple paragraphs above, we talk about planting the leeks deeply to help blanch the stem. The purpose of mounding the soil is to continue this blanching process. Blanching is a technique used to shade plant parts from sunlight to prevent greening. With leeks, it helps create that succulent white bulb we all love. Without blanching (or mounding of the soil), you’d get more tough green stems and less white bulb. Happy growing!

      Kelly, Bonnie Plants

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