In all our years gardening, and with a seemingly endless list of veggie varieties we’ve grown, we discovered leeks later in our gardening game. But once we started growing leeks, I was like: where have you been all my life? Leeks are delicious, beautiful, fun and easy to grow (albeit a tad slow). Yet their journey to maturation is a laid back one, as very few pests bother leeks, and they’re also frost-tolerant.
Ready to become a certified leek geek? Read along to learn how to grow leeks, from seed through harvest and beyond. We’ll talk about the best time of year to grow leeks, starting seeds, transplanting seedlings, ongoing care, and different varieties of leeks to grow. After harvest, we’ll also cover several ways to store, preserve, and eat fresh leeks – including leek greens!
What are Leeks?
Leeks are part of the Allium family, alongside onions, scallions, and garlic. They have an onion-like flavor, but are far more mild and sweet. Unlike many alliums, leeks don’t form bulbs. Instead, they’re easily recognized by their long, thick, cylindrical white stalk. Atop their stalk, leeks grow a fan of wide, flat, blue-green leaves – which can be a bit tough but are also edible! Leeks are considered a cool-season crop, though they are adapted to growing in a wide range of temperatures, much like onions.
Nutritionally speaking, leeks are rockstars! While low in calories, they boast an impressive amount of vitamins and minerals including manganese, iron, folate, vitamin K, vitamin B6 and vitamin C. Like the rest of the allium family, leeks also contain an high amount of flavonoid antioxidants. According to WebMD “Flavonoids are antioxidants and may have anti-inflammatory, anti-diabetic, and anticancer properties, as well as other health benefits.”
Growing Leeks: At a Glance
- Days to maturity: 55 to 180 days after transplanting, depending on variety.
- Temperature: Leeks thrive in temperatures 55-75°F. They can tolerate hotter weather, though their growth rate may decline.
- Planting time: Spring in northern climates. Spring or late summer to fall in mild southern climates.
- Direct sow or transplant: starting leek seeds indoors to transplant later is preferable in most cases.
- Plant spacing: 6 inches apart, plant seedlings 3-6 inches deep.
- Growing preferences: full sun, ample consistent water, well-draining soil, moderate nitrogen and organic matter.
- Frost tolerant: Yes, once mature (seedlings are not).
- Pests: few, including thrips, maggots, and fungal diseases.
Types of Leeks: Short vs Long Season
Leek varieties fall into one of two general categories: long season or short.
Short season leeks, also known as “early season” leeks, are ready to harvest within 50-100 days of planting seedlings. Short season leeks are generally smaller, more mild-tasting, and less hardy than long season leeks. Yet they are ideal for gardeners with a short cool-season growing window. Popular short season leek varieties include King Richard, Varna, Rally and Lancelot.
On the other hand, long season leek varieties need more than 100 days to reach maturity – some up to 180 days after transplanting! Even more, long season leeks can often be left in the ground for “storage” after they reach maturity, for up to 210 days (or until the ground freezes). These leeks are larger, more cold-tolerant, and can be stored longer – including in the ground or after harvest. Long season leeks also benefit from blanching, described more to follow.
Sometimes you’ll also see a third “mid-season” leek category, capturing the leeks that take 90-120 days to mature in their own intermediate group. The vast majority of leek varieties are mid to long season types.
When to Plant Leeks
When is the best time to plant leeks, you wonder? Most gardeners plant short season leeks in the spring to harvest in summer to early fall. In the north, long season leeks are also planted in spring, but can be harvested up until the ground freezes. Mature leeks are frost-tolerant.
Southern gardeners with mild, virtually frost-free winters have more flexibility. They too can plant leeks in spring, as well as in late summer or fall as part of their winter garden. Fall-planted leeks can overwinter to harvest in late winter or spring. Here on the temperate Central Coast of California, we grow leeks year-round!
For spring planting, start leek seeds indoors in late winter about 8 to 10 weeks before your area’s last spring frost date. Transplant leek seedlings outside after the last risk of spring frost has passed. See more tips about growing leeks from seed below.
To determine the best time to start leek seeds and transplant them outdoors for your particular zone, check out the Homestead and Chill planting calendars – available for every USDA hardiness zone!
Growing Leeks from Seed or Seedlings
There are two ways to grow leeks: start them from seed yourself, or purchase already-started seedlings to plant. We have done both, but usually prefer to start from seed.
One key benefit of growing leeks from seed is the ability to choose specific varieties that sound intriguing or most suitable for your climate. For instance, we look for leek varieties that are naturally resistant to rust – a fungal disease that affects the allium family, which is fairly common in our area.
Yet there is nothing wrong with growing leeks from nursery seedlings either! (If you can find them at your local garden center, that is.) Nursery seedlings are especially convenient if you don’t have seed starting supplies, have a short growing season, and/or didn’t start seeds on time.
Should I start leek seeds indoors or direct-sow leeks outside?
To grow leeks from seed, you’ll find the most success by starting the seeds indoors (or in a greenhouse) in containers and transplanting seedlings outside later.
While you technically can direct-sow leek seeds outside, I don’t usually recommend it since the seeds can be finicky to germinate. Plus, long-season leek varieties will greatly benefit from the jump start they’ll get inside – much sooner than you could start them outside in colder climates. Last but not least, starting leeks from seed in a container allows you to bury the leek stem deeper come transplant time, which helps promote the most upright, tender, and delicious leeks.
Tips for Starting Leek Seeds Indoors
- Start spring leek seeds indoors about 8 to 10 weeks before your area’s last frost date (usually in mid to late winter). For fall planting in mild climates, start leek seeds in late summer.
- Plant leek seeds in fresh, sterile, fluffy seed-starting mix.
- You can start leek seeds in traditional seedling cell trays or “6 packs”, planting a few seeds per cell. Or, scatter seeds (not too heavily) across a single large shallow tray of seedling soil, and thin/separate the seedlings later – also known as the multi-sow method.
- Sow leek seeds ¼” deep, covered only lightly with soil (not compacted).
- Spacing leek seeds at least 1/4″ to 1/2″ apart will make it easier to separate the seedlings later.
- Ideal soil temperature for leek seeds to sprout is around 70°F. They can germinate in cooler temperatures, though at a much slower rate. Use a seedling heat mat to promote quick and even germination.
- Maintain the seedling soil damp (but not soggy) at all times. Keep the trays covered with a humidity dome before germination to prevent the soil from drying out. Uncover once they sprout.
- Leek seeds are fairly slow to sprout, so be patient! They should germinate within 2 weeks, or about 10 days on average.
- As soon as they sprout, provide ample bright light for at least 12 to 16 hours per day. Grow lights are highly recommended when starting seeds indoors.
- When in doubt, follow the instructions provided on your seed package.
- See our seed starting guide for more detailed information on starting and caring for seedlings indoors.
How to Plant Leeks (Transplant Leek Seedlings)
Once the leek seedlings are at least 7 to 8 inches tall and about as thick as a pencil, it’s time to plant your leeks outside! Whether you are growing leeks from seed or purchased seedlings, the following transplanting tips apply:
- Before transplanting, ensure indoor-raised seedlings have been hardened off first. The hardening off process reduces the risk for transplant shock or injury. Learn more here.
- Transplant leek seedlings outdoors in spring after the last risk of frost has passed. Keep an eye on the weather forecast and be prepared to protect seedlings from frost if needed. Mature leeks can withstand a light frost (especially long-season varieties) but tender seedlings are far more susceptible to frost damage.
- Gently separate or pull apart any leek seedlings that may still be clustered in the same seedling pot or tray. Remove the root ball from the container, gently loosen the soil, and slowly untangle the leeks – taking care to not to break the roots or seedlings.
- Plant, space or thin each leek seedling about 6 inches apart. Adequate spacing is essential for leeks to grow to their potential size!
- Dig a trench approximately 6 inches deep, or use a dibble or small trowel to create 3 to 6-inch deep holes.
- You can plant leek seedlings deep, with a majority of the stem buried and only a couple inches of green tips showing above the soil line (see depth discussion below).
- Gently and loosely backfill, but don’t compact the soil around the seedling stem. Or, don’t backfill at all and let the holes fill in on their own with time.
How deep should I plant leek seedlings?
This deserves it’s own discussion because there is a lot of confusion and conflicting information out there about transplanting leek seedlings. Most garden experts recommend planting leek seedlings deep (up to 6″, with most of the stem buried) to reduce the need for blanching. Planting leeks deep will result in a longer white stalk, which some folks find more desirable. Yet deeply-planted or hilled leeks may also harbor more dirt inside this way – so there’s a tradeoff.
However, you don’t have to bury them so deep. Leeks grow just fine if only minimally buried, planted 2-3″ deep. Their stalk color will simply be light green instead of pearly white. If you desire extra-white leeks, you can always blanch them later after planting (read more below). Or, simply let them grow au natural like we usually do!
Leek Growing Requirements: Sun, Soil, Fertilizer, Water & Mulch
- To grow the best leeks, choose a location that receives ample sun. Leeks will tolerate partial shade but grow most vigorously in full sun.
- You can grow leeks in the ground, in raised garden beds, or even in large grow bags.
- Leeks grow best in well-draining soil that is rich with organic matter. If needed, amend clay or heavy soils with quality potting soil and/or horticulture sand to promote good drainage.
- Leeks are fairly heavy feeders and enjoy ample nitrogen. Before planting, add a couple inches of well-aged compost to the soil. We also add a sprinkle of slow-release organic fertilizer, gently scratched into the top of the soil. Long season leeks may benefit from a mid-season feeding of compost tea, dilute seaweed extract, fish fertilizer, or a side dressing of mild slow-release granular fertilizer. Avoid strong fertilizers mid-season, as it could trigger leeks to bolt.
- Leeks thrive with consistent moisture. Therefore, water leeks regularly enough to maintain the soil damp (though not soggy) at all times.
- Mulch around the base of leeks (once they’re no longer tender seedlings) to help with moisture retention and insulate against temperature extremes. One to two inches of mulch is adequate for leek seedlings that were initially buried 4 to 6” deep. Provide a deeper layer of mulch for shallowly-planted seedlings (see ‘blanching’ below) or when freezing conditions are expected.
Blanching is the act of covering or hilling soil around leek stalks as they grow, blocking sunlight from the lower portion. It encourages the leaves to grow higher up the plant and results in a longer, whiter stalk. Un-blanched leek stalks are light green instead. Certain leek varieties are “self-blanching” and produce white stalks even when exposed to the sun while growing.
Some folks claim that the more white and blanched the stalk, the more tender and sweet the leek is. However, this claim has also been repeatedly refuted in blind taste tests when comparing blanched to un-blanched leeks. So, it seems blanching is more about aesthetic than anything.
To blanch leeks, simply hill up soil or mulch around the base of the plant, burying a couple inches of the stalk (but not too high or dirt will end up between the leaves). Do this two or three times throughout the growing season, hilling higher each time. Another way to blanch leeks is to cover or wrap their stalks, such as with cut cardboard tubes made from toilet paper or paper towel rolls.
Blanching is most useful when leek seeds are directly sown outside, or if seedlings are buried shallowly when they’re first transplanted. When leeks seedlings are transplanted deeply with the “dibble method” or in deep trenches, the need for hilling is reduced or eliminated. It’s also less necessary when growing short-season leek varieties.
Leek Pests & Diseases
Thankfully, leeks are inflicted by few pests compared to most garden crops, making them relatively fuss-free to grow. Rather, leeks, onions, and other members of the allium family naturally deter many pest insects! Leeks are most susceptible to pests or diseases that affect onions.
The most common leek pests include:
- Onion thrips are tiny yellow-brown colored leaf-sucking insects. They are fairly common but most prolific in hot, dry conditions. They concentrate in tight folds between leaves and focus their feeding on new succulent growth. Organic management strategies include neem oil spray, biological control with beneficial insects (such as lacewing larvae and predatory thrips) and the removal of heavily infested plants.
- Onion maggots are the larvae from the onion maggot fly. Similar size to a housefly, onion maggot flies lay eggs near the base of allium plants, where their larvae will emerge and begin to feed. They feed on allium seedlings, roots and bulbs, causing wilting or reduced growth. Onion maggots thrive in cooler damp conditions (especially coastal climates) and are not as bothersome in hot arid climates. As natural predators to maggots and grubs, the application of beneficial nematodes is an excellent and effective organic onion maggot control option.
- Allium Leaf Miners are invasive insects from Poland, and are currently only found in the Northeast and Mid-Atlantic regions of the U.S. The fly-like pests pierce and feed on plant sap, and lay eggs within the plant tissues.
- Leek moth is found in Canada, Asia, Europe and Africa, though not yet in the continental United States.
- Fungal diseases such as allium rust, downy mildew, pink rot, white rot, and Botrytis leaf blight. Homemade neem oil spray can help reduce the spread and damage caused by most fungal diseases. Dilute potassium bicarbonate spray is another effective organic fungicide. Check out our article on powdery mildew control for more details on using both solutions.
Flowering or Bolting Leeks
Us gardeners grow leeks as annual crops, though they’re technically biennials. That means if they’re left long enough in the ground (beyond their prime harvest time), they will form a center flowering stalk and eventually produce seeds. Leeks may also form a flowering stalk prematurely, referred to as “bolting” or “going to seed”.
Leeks may bolt when presented with unfavorable growing conditions, such as too little or irregular water, too much fertilizer (especially high phosphorus fertilizer), or too little sunlight. Unlike many garden veggies that bolt due to hot weather, consistently cold conditions (e.g. daytime temperatures regularly under 45°F) can cause leeks to bolt instead. The best way to prevent leeks from bolting is to grow leeks at the right time of year for your climate, and transplant seedlings before they become too large or root-bound.
Once leeks begin to flower, their stalks and leaves become increasingly tough, woody and bitter (though still technically edible). Therefore, if you notice your leeks start to flower, harvest them as soon as possible since the quality will only continue to decline. That is, unless you want to leave the flowers to enjoy! They’re quite beautiful, and popular with the pollinators too.
When and How to Harvest Leeks
Harvest leeks once they’ve reached the desired size. Check the description of the particular leek variety you are growing to determine their expected maturation time and size. Like onions, you can harvest leeks early and enjoy them as tender premature versions of their adult selves if you’d like!
One of the beautiful things about growing leeks is that you don’t have to harvest them all at once. Long season leek varieties can be left and stored in the ground until you’re ready for them – as long as they don’t begin to flower and aren’t exposed to a hard freeze (though they’re frost tolerant). When hard freezing conditions are expected, either harvest the leeks or protect them with mulch and horticultural fleece.
When it comes time to harvest leeks, remember: DIG, don’t pull! Leeks can be deep-rooted in the soil, and pulling up on them risks breaking the precious stalk. Instead, carefully insert a small trowel or spading fork straight down into the soil near the stem to gently loosen and lift the leek upwards from below.
Storing Fresh Leeks
After harvest, avoid washing or trimming the leeks until you’re ready to use them. (That is, unless you intend to use them within the next few days). You can trim off the dirty roots, but don’t cut into the stalk itself. Store fresh leeks in the refrigerator tucked inside a plastic bag (or two, if they’re extra tall). Refrigerated leeks should stay good for at least a week or two, sometimes longer.
Another option to store fresh leeks is in a root cellar, ideally between 32 and 40°F. After harvest, transfer the leeks (unwashed, roots still intact) into a bucket of horticulture sand or fresh potting soil. Stand them upright in the sand/soil and cover several inches of the bottom stalk. Certain leek varieties can stay good for several months in a root cellar!
Ways to Eat Leeks (and Leek Greens)
Leeks are a wonderful mild substitute for onion in any recipe. The tender stalks are fantastic thinly-sliced on top of pizza, sourdough focaccia, in stir-fry, pasta or rice dishes, omelets and quiche, soups, sauces, and more. They’re also fantastic grilled, or turned into pesto. Then of course perhaps leek’s most renowned use: potato leek soup! Try our creamy vegan potato leek soup recipe here.
How to Prepare Leeks
The cylindrical stalk is the most edible, tender, and delicious portion of the leek. To prepare leeks, cut off the firm root end as well as the upper leafy green portion. (But don’t discard those just yet!) Peel away a few outer layers of the stalk if needed; they may be more tough or dirty. Finally, thinly slice the stalk into rounds to use in your recipe of choice.
Since leeks are grown partially underground they can be quite dirty, including hiding between the layers of leaves. In addition to running them under water, you can clean leeks by soaking cut leeks in a bowl of water if needed. The dirt will settle to the bottom of the bowl, while the leek pieces will float and can be scooped out. (I’ve found commercially grown leeks to be far more dirty than our homegrown leeks, and don’t usually need to soak ours).
Can you eat leek greens?
Yes, you absolutely can eat leek greens! Yet they can be quite tough and chewy, especially the uppermost portion. Therefore, I suggest using the lower leek greens (closer to the white stalk) for cooking applications. Thinly-sliced, those leek greens make a great addition to soup or other recipes where they can cook long enough to soften. Or, if they get blended up – like added to our besto pesto recipe. Yet our favorite way to use leek greens is to dehydrate and turn them into leek powder. We use some of the toughest top leek greens for that!
Can you eat leeks raw?
Sure can! Just as you can eat raw onions, raw leeks offer an even more mild (and more enjoyable, in my opinion) pop of flavor to many meals. Add thinly-sliced raw leek stalks mixed into salads (including potato or pasta salad), dips, pesto, or homemade salad dressings. They’re also great as a garnish on top of roasted veggies, sandwiches, egg dishes, soups, salads, and more. I personally would not eat tough leek greens raw.
Fresh leeks can be frozen, dehydrated, canned, fermented or pickled. We love to preserve leeks by drying them to make leek powder. The result is a delicious sweet onion-like seasoning powder. Learn how to make and use leek green powder here. Freezing leeks is also easy, explained below. Another great way to preserve leeks is to freeze potato leek soup!
Freezing leeks is a great way to preserve leeks when you have more than you can eat fresh. Later, frozen leeks can be added to soups, sauces, or other recipes that call for cooked leeks. However, their texture won’t be quite as great as fresh leeks.
To freeze leeks, cut them into thin rounds so they’re ready to use without further preparation after thawing. Line a baking sheet or other tray that can fit in your freezer with parchment paper, then lay the cut leeks out in a single layer. Next, freeze the tray until the leeks are frozen solid (overnight or 24 hours).
Finally, transfer the individually-frozen leek pieces into a freezer safe storage container and place back in the freezer for final storage. Move quickly so they don’t defrost while you work. This way, the leeks won’t stick together into one solid clump, making it easier to pull out just a portion of them as needed.
And now you know how to grow leeks – and then some!
In closing, I hope this article boosted your confidence and excitement about growing leeks. Between their easy care, unique appearance, and versatility in the kitchen, they’ve certainly become a staple in our garden! Please let me know if you have any lingering questions that I didn’t address in the comments below. If you found this article to be helpful, please feel free to spread the leek love by pinning or sharing this post. Thank you so much for reading!
Ready to learn more? Don’t miss these awesome grow guides:
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- Potato Grow Guide
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