Leeks aren't at the top of most gardeners' lists, but they should be. Space-efficient, low-maintenance, and with wonderful flavor, leeks are perfect for home gardeners. Learn to grow them, and you'll have leeks for tasty recipes like the traditional potato-leek soup, one of my favorite winter comfort foods. Try our recipe for sautéed leeks, too. 

Unlike run-of-the-mill onions, leeks have flat leaves and don't make much of a bulb. The edible part resembles a green onion. Their foliage is bluish-green and makes an attractive upright display. Leeks are most often grown as annuals, but they are actually perennials (although most folks call them biennials). Leeks left overwinter will grow a scape like garlic in the second year and set seed. 

Leeks are an Allium, like onions, garlic, and shallots, and are botanically known as Allium porrum. Some leeks are more cold-hardy than others, which is a consideration when choosing varieties to grow. 

Most leeks vary in maturity from about 100 to 130 days. Leeks vary in size, with the aptly named Dawn Giant being one of the largest (and easiest to grow) leeks available. For superior flavor, try the classic American Flag leek.

Leeks can also be grown in a container on the patio or back porch, making them a perfect choice for gardeners limited in space. 

How to Plant Leeks

Leeks are normally started indoors from seed, which gives you something to do in winter when you've got the gardening itch but nothing is ready outside. Order your seeds early because you'll need to start leeks about ten weeks before your last frost in spring to have them ready for transplanting. They're a bit slow to start, but they'll pick up. 

Leeks do best in full sunshine and may grow intolerably slow or not at all in shadier locations. Some quicker to mature can be directly seeded in the garden in spring and then thinned as they start to fill out for use in the kitchen like green onions. 

Starting Leek Seeds

One packet of leeks will provide all but the most diehard leek fans with more than enough seed—200 leeks, anybody? If you aren't looking for (or don't have room for) a leek forest, you can start a couple dozen leeks in a sour cream container and grow them in a few square feet of bed.

Leeks can be planted in soil blocks, standard cell trays, or scattered in an undivided tray and transplanted or pricked out later. Any good potting mix or seed starting mix will work. 

• Premoisten the mix and fill the container.
• Plant leek seeds about ¼" deep. They're small and hard to plant, so a seed sower can help avoid dropping too many at once.
• Use a toothpick to push the leek seeds down a quarter inch into the soil or cover them with a layer of soil mix and vermiculite.
• Once leeks sprout, keep them slightly moist. The seedlings will look like grass for a while and can be grown quite close together. 

Preparing Beds for Leeks

Leeks love loamy, rich soil amended with compost. While leek roots are shallow, it's still a good idea to loosen the soil with a garden fork to help with drainage. It's also the perfect way to lightly work a layer of compost into the top few inches without doing extra work.

Leeks will do better than regular onions in heavy soil, but if your native soil leans towards clay, you might have easier success in raised beds.

Transplanting Leeks

Ideally, leeks will be about the size of a pencil when ready for transplanting and about eight inches tall. They are frost-tolerant and can be planted outdoors a couple of weeks before the last frost date.

Harden off your leek seedlings before putting them out to fend for themselves in your garden. Space leeks about 3–4 inches apart for tight spacing or 6–9 inches apart for large varieties.

Many folks like to hill their leeks, similar to how potatoes are hilled. Hilling leeks help to blanch them, providing that white stem you may be familiar with and making it longer. However, I must confess, I don't normally go to the bother of it. If you'd like to try hilling leeks, there are two methods. 

1. Plant leeks in a trench about 4–6 inches deep. As they grow, push a bit more soil into the trench. After a few weeks, repeat it until the trench has been filled in. It's kind of a reverse mound; instead of starting flat and piling soil up, you'll start below the ground level and fill it in. This method works well for raised beds where mounds of soil above the edges might be an issue.
2. Plant leeks at normal depth and hill up or mound soil around them as they grow until the mound is 4–6 inches tall. Take care you don’t push them over when mounding.

Planting Leeks in Containers

Leeks can be transplanted into containers or simply sown in pots and moved outside once the weather warms. Use a large pot filled with quality potting soil, and ensure the drainage holes are open. 

On many new plastic pots, the drainage holes need to be popped out with a tool like a screwdriver (be careful). Plant the leeks as above, but instead of hilling them, you'll just plant them deeper to begin with. Use a dibble or stick to make the hole. Leeks in pots can be planted more closely because you’ll be pampering them with frequent water and fertilizer.

Growing Leeks

Leeks are pretty low-key regarding garden tasks but do not compete well with weeds. Mulching leeks will keep the weeds down and your garden looking tidy, help with soil moisture, and reduce the frequency you need to water. Leeks are a great crop to plant in harder-to-reach sections of your garden bed, since you won’t need to access them frequently.

Leeks in the garden need about an inch of water per week, more in hot, dry conditions. Those in containers may need more frequent watering since containers dry out more quickly than garden soil.

Harvesting Leeks

Growing leeks is a patience exercise, but eventually, you'll start eyeing them up and wondering if they might not be on the menu soon. Since they don't die off in autumn with the frosts, you can enjoy an extended harvest from summer right into winter.

When are leeks ready to harvest?

Leeks can be harvested as soon as they've reached the size you are looking for. Since they aren't making a fruit like a tomato or bean, there is no set time to call them ready. 

Most varieties are at prime harvest time when the base of the stalks are about an inch in diameter. However, some varieties are bred to get much larger. If your leeks are crowded, harvest some early as a thinning.

Leaving them in the ground

You can leave leeks right in the ground in many climates. Long-season (sometimes called late-season) leeks are more cold-hardy than shorter-maturity varieties. Leeks don't die in the fall; they just grow much more slowly. If the ground doesn't freeze hard, making them difficult to dig, you can let them stay right in the garden bed and harvest them as needed for the best flavor. 

Leeks are quite frost tolerant once they have become established. Last fall, I forgot some smaller ones that I was letting get larger and left them out all winter with no mulch or anything else. They survived below-zero temperatures and started growing again this spring. 

Storage

As mentioned, leeks are best stored in the ground to preserve their flavor. Mound up soil or even cover them almost completely with mulch. Harvested, they can be kept in the refrigerator for about a week or ten days or chopped up and frozen for later additions to soups or other dishes.

Once you've dug them up, trim off the roots (leave the base intact until use) and the upper ends of the leaves. While the thick, white stalk is normally used in cooking, save the remaining green leaves for flavoring if you make your own soup stock.

Washing and Prep

Leeks have a bad reputation for having "dirt" between the layers. It's partially a matter of how they are grown—mulch reduces the problem—but all leeks can get some soil stuck up there. Wash them in the sink with lots of running water. If the recipe calls for slicing them and you still find a bit of grit, give them a rinse in a colander or strainer.

Most recipes call for the white portion of the stalk, but the entire plant, minus the roots, is edible and flavorful. The stiff green leaves are best left to flavor soups and other dishes rather than eaten alone.