Leek Plant Guide: How to Grow Leeks From Seed to Winter Harvest

To grow a leek plant, sow the seed indoors in winter, 10 to 12 weeks before your last spring frost on a seed company's schedule, or 4 to 10 weeks ahead in Wisconsin. Drop pencil-thick seedlings into holes or a trench about 6 inches deep, let soil fill in around them as they grow, and space them roughly 4 to 6 inches apart. Keep the shallow roots watered. Leeks are ready once the shaft is about 1 inch thick, usually 100 to 150 days after planting out or after seeding, depending on the variety and on how a guide counts, and hardy types can stand in the ground through frosts into winter.

When to plant leeks

Plant leeks by starting seed indoors in winter, well before the last spring frost, then setting the seedlings out in spring once they are about pencil-thick. Leeks are a long-season crop, so the calendar starts early:

• A seed company's schedule: sow in flats 10 to 12 weeks before the last frost; plant out from late spring at about 8 inches tall and pencil-thick.
• In Wisconsin: indoors 4 to 10 weeks earlier than the state's average last spring frost, then plant out from late April or early May, as the plants take light frost.

Other guides time it by their own climate. One grows transplants for 6 to 8 weeks and sets them out in early April in Utah. In northern climates, another sows in late February or March and plants out once daytime temperatures reach at least 45 F. A third notes that leeks are fairly hardy and can go out several weeks before the last frost date.

The table below puts the seed company's 10 to 12 week window on the calendar at four weather stations. A freeze date here is the 1991 to 2020 normal for the last spring or first fall 32 F night; in half of years it comes earlier, in half later.

When to sow leeks indoors at four weather stations

Station	Indoor sowing (10 to 12 weeks before)	Spring freeze date	Fall freeze date
Minneapolis-St. Paul, MN	Jan 29 to Feb 12	Apr 23	Oct 18
Baltimore (BWI), MD	Jan 16 to Jan 30	Apr 10	Oct 31
Raleigh-Durham, NC	Jan 6 to Jan 20	Mar 31	Nov 4
Dallas-Fort Worth, TX	Dec 14 to Dec 28 (of the year before)	Mar 8	Nov 24

Indoor sowing = 12 to 10 weeks before the spring freeze date; reading the seed company's "last frost" as that 50 percent date is our reading, and a frost after it is still as likely as not. The 4 to 10 week window is written for a single state, so the table does not apply it to these stations.

Fall sowing in Florida. Leeks are sown in the fall there, for a harvest in three to four months. Elsewhere, look up the freeze dates for your nearest weather station: hardiness zones carry no frost dates.

Which leek planting fits your calendar

Your distance from the last spring frost settles the first step; answer the questions from the top.

Starting leek seeds indoors

Sow leek seed 1/4 inch deep, about 1/4 inch apart in a flat or one plant per plug cell. Keep the mix at about 70 F until the seedlings emerge, then give them strong light.

Trimming and hardening off. One guide cuts seedlings back to 1 1/2 to 2 inches once they reach 6 to 7 inches tall; the clippings work like chives. Another sets them out at 10 to 15 weeks old at most, after five to seven days of hardening off.

Sowing direct instead. Leeks can also be sown straight into the garden in early spring, at a depth between a quarter and a half inch, thinned to 4 to 6 inches in rows 8 to 24 inches apart. Add 20 to 30 days to a seed company's days to maturity, which count from transplanting. Direct sowing gives smaller plants.

Transplanting leeks: trenches, holes and hilling

The white part of a leek is stem grown out of the light, so plant deep, into a hole or trench 5 to 8 inches deep: holes run about 6 inches (5 to 6 in one guide), and a trench 6 to 8.

The dibble method. Push a stick into loose soil for each hole: a dowel roughly 1 to 1 1/4 inches across, or a rake handle. Drop in one seedling so only 2 to 3 inches of leaf shows, or set it down to the first leaf notch. Do not backfill or firm the soil at planting; water gently and let rain or irrigation wash soil in.

As they grow. Fill the dibble hole in gradually, and pull soil up around the plants as they mature for a longer white stem. In a trench, fill in bit by bit up to where the leaves spread. Plants set at normal soil level are hilled instead, with soil mounded around them several times as they grow: 2 or 3 times in two guides, higher each time, one adding 2 to 3 inches at each hilling of seeded plants. The dibble method reduces the hilling needed and can do away with it. Blanching is optional: it makes leeks more tender and mild.

Summer leeks vs overwintering leeks

One guide splits leeks into summer types, harvested the season they are planted, and overwintering types, harvested the next spring; summer types generally run smaller, and overwintering types are generally stronger in flavor. A seed company sorts its varieties into four harvest slots instead, from summer through late summer and fall to winter. The trade-off: faster-growing leeks are less cold tolerant, slower ones hardier. Days to maturity vary by listing (the seed company counts from transplanting):

• 'King Richard': 75 days, and can survive down to 20 F; on one guide's list of recommended varieties.
• 'Bandit': 105 or 120 days, depending on the listing; very winter hardy in both.
• 'American Flag': 130 days and hardy to about 10 F; 'Large American Flag' is on one guide's recommended list.
• 'Giant Musselburgh': 150 days, and very hardy or cold-hardy in the two guides that list it.

One northern guide puts most leeks at about 120 to 150 days, but some newer varieties at as few as 90, and says these may suit Minnesota conditions most. For a long harvest, sow varieties of differing maturity together, on one day.

Spacing, feeding and watering leeks

Spacing. Leeks sit close: 2 to 6 inches apart in most guides, though one sets them 6 to 9 inches apart in a home bed, or 4 to 6 inches in larger plantings. Guides turn the leaf fans differently: one points the leaves into the space between rows, away from neighbors, while another runs them along a staggered double row to keep them out of the path.

Soil and feeding. Guides disagree on appetite: a seed company calls leeks heavy feeders wanting pH 6.2 to 6.8, while another guide rates their needs light to medium. Test the soil first, then side-dress once or twice between mid-May and mid-summer.

Water and weeds. Roots are shallow, so one inch of water a week, from rain or the hose, aimed at the soil rather than the leaves, is enough; one guide wets the soil 18 inches deep every 7 days. Young leeks grow slowly and lose out to weeds, so weed control is particularly important in their first 2 months.

The figures side by side, by the region each guide writes for:

How leek timing and depth vary by region

Region	Indoor start	Planting depth	Days to maturity	Cold
MD	Indoors for spring; later in summer for fall	Holes 5 to 6 in	70 to 120; usually 100 to 120 after planting	Takes heavy frost; dig all winter under mulch
MN	Late Feb or March (northern climates)	Furrow 6 in, or hill	Most need about 120 to 150; some 90	Some varieties come through 20 F
WI	4 to 10 weeks before last frost	Holes about 6 in; trench 6 to 8 in	80 to 120 or more	Dig before the ground freezes solid (typical winter)
UT	6 to 8 weeks of growth	Dibble hole 6 in	From 60; usually 100 to 120 after seeding	Leave in the garden in milder areas
FL	Sow in fall	Mound soil from pencil width	Three to four months	A winter crop
Seed company (any region)	10 to 12 weeks before last frost	Dibble hole 6 in, 2 to 3 in of leaf showing	75 to 105 from transplanting; add 20 to 30 if direct sown	Slower varieties are the hardier ones

When to harvest leeks

Harvest leeks when the shaft is about 1 inch thick: they are ready at 1 inch in diameter, and can be dug any time after they reach an inch or more. Two guides put that at usually 100 to 120 days, one counting from planting and one from seeding, and both say harvest can start as early as 60 days, when leeks are about green onion size. A northern guide puts most leeks at about 120 to 150 days, while a seed company's varieties run 75 to 105 days from transplanting.

What a ready leek looks like. Look for a firm white shaft more than 3 inches long; a swollen, bulb-like base is a fault. Leeks do not go dormant in fall but keep growing slowly, so the date is flexible: let them wait in the bed until you need them.

How to dig leeks. Loosen each plant with a spading fork and lift it, or twist and pull it gently; leeks have large roots, so digging is sometimes easier than pulling. Slice each leek lengthwise to rinse out soil caught between the layers.

Storing leeks. In the refrigerator, guides give anywhere from 7 to 10 days to at least a month, though quality falls short of fresh-picked. Cleaned leeks also keep for several weeks near freezing in a humid cooler, or at 32 to 40 F in humid conditions such as wet sand.

Leaving leeks in the ground over winter

Where winters allow, the garden itself is the long-term store for leeks. Each guide speaks for its own region:

• Maryland: hill soil around the plants, spread heavy straw or leaves over them in fall, and dig all winter.
• Utah: in milder parts of the state, hill and mulch them in place; in very cold areas, dig them and store them cold and humid.
• Minnesota: leeks take the first few frosts, and some varieties may come through 20 F unharmed; heap mulch around them and dig into late fall.
• Wisconsin: harvest can run through a mild winter into early spring, and an extra-thick mulch delays the ground freezing; in a typical winter there, dig before the ground freezes solid.
• Florida: leeks are a crop for the winter garden, sown in fall.

Our reading: frozen ground is the practical limit. Leeks can stay put as long as the ground is not frozen, and a thick mulch puts the freeze off. Where your ground will freeze solid, dig the leeks first and keep them as under Storing leeks above (32 to 40 F, humid).

Leek pests: thrips, onion maggot and leek moth

Leeks have few pests, but most onion pests and diseases can attack them.

• Onion thrips are quite common by one account and occasional by another; they cause problems mainly in hot, dry weather, leaving tiny silvery-white specks.
• Onion maggot can feed on roots and bores into stems, so plants yellow and wilt.
• Leek moth is a small leaf-mining caterpillar. A 2011 extension sheet from Clinton County, New York, reported the first confirmed sighting in the continental United States at Plattsburgh in 2009. On leeks the larvae eat the leaf surface and often hide inside the folded leaves. The sheet's controls include row cover straight after planting so moths cannot lay eggs, and raking up crop debris at season's end, where adults overwinter. That sheet is dated; ask your local extension office whether leek moth is found near you.

Rust, white rot, downy mildew, purple blotch, pink root and others may occur, though they are uncommon in home gardens, and rot can occur in soggy, poorly drained soil.

Seeds and supplies

Pick varieties by when you want to eat them: an early type such as 'King Richard', plus a slow, hardy type such as 'Bandit', 'American Flag' or 'Giant Musselburgh' for leeks that stand into the cold. Beyond seed: a seed tray for the indoor start, a soil test before feeding, and fine insect netting where leek moth is found.

What you'll need for leeks

As an Amazon Associate we earn from qualifying purchases.

• 

  Survival Garden Seeds American Flag Leek Seeds

  Hardy to about 10 F; 'Large American Flag' is on one guide's recommended list.

  Check price on Amazon
• 

  Thresh Seed Co. Giant Musselburgh Leek Seeds

  150 days, and very hardy or cold-hardy in the two guides that list it.

  Check price on Amazon
• 

  Burpee 72 Cell Greenhouse Kit

  A seed tray for the indoor start.

  Check price on Amazon
• 

  Luster Leaf 1601 Rapitest Soil Test Kit

  A soil test before feeding.

  Check price on Amazon

Sources we used

All of the pages listed were read in October 2026. Where their leek figures differ, this guide gives the range or both readings.

• "University of Maryland Extension: Growing Leeks in a Home Garden"
• "University of Minnesota Extension: Growing leeks in home gardens"
• "University of Wisconsin-Madison Extension: Leeks"
• "Utah State University Extension: How to Grow Leeks in Your Garden"
• "UF/IFAS Gardening Solutions: Leeks"
• "NC State Extension Plant Toolbox: Allium ampeloprasum"
• "Cornell Cooperative Extension, Clinton County: Leek Moth 2010 Update" (revised July 2011)
• "Johnny's Selected Seeds: Leeks Key Growing Information", plus its leek harvest program chart and leek variety list
• "NOAA NCEI: U.S. Climate Normals, 1991-2020", which supplies the station freeze normals

Related guides

• Growing garlic from fall cloves; elephant garlic is really a type of leek
• How to grow kale, which also stands in the garden into winter
• How to grow carrots, which can also wait under mulch in the bed
• How to grow turnips and rutabagas, for the rest of the fall bed
• How to grow chicory, more cold-season harvests
• Seed starting trays buying guide, trays and flats for the winter sowing indoors

Frequently asked questions

When should I start leek seeds?

Indoors, 10 to 12 weeks before your last spring frost on a seed company's schedule; in Wisconsin, 4 to 10 weeks. In Florida, leeks are sown in the fall instead.

When do you harvest leeks?

When the shaft is about 1 inch across, usually 100 to 150 days after planting out or after seeding, depending on the variety and on how a guide counts. There is no rush: they keep growing slowly in fall and can wait in the ground.

Can leeks stay in the ground over winter?

Often, yes. Under a heavy mulch, leeks can stay in the ground and be dug through a mild winter. Where the ground freezes solid, dig them first.

How cold can leeks survive?

It depends on the variety. Some varieties may take 20 F unharmed, 'American Flag' is rated hardy to about 10 F, and the slower-growing varieties are the hardier ones.

Do you have to hill leeks?

No. Hilling makes a longer white, milder stem, but it is optional, and planting into 6-inch dibble holes reduces the hilling needed.

Do leeks come back every year?

Guides differ: one calls the leek a true perennial usually grown as an annual, another a biennial treated as an annual. Leeks left into spring flower and set seed, and bulblets at the base can start a new crop.