Growing Leeks: A Simple Guide to Planting and Care

Why I keep a bed of leeks every year

I keep coming back to Growing Leeks because they stand tall when everything else sulks in the cold. In January soup weather, those blue-green flags feel like a quiet victory.

Leek basics at a glance

• Botany: Allium porrum, a hardy biennial grown as an annual.
• Soil pH: 6.2 to 6.8 for steady growth and mild flavor.
• Timing: 90 to 150 days to harvest, depending on variety and season.
• Spacing: 6 to 8 in apart (15 to 20 cm), rows 12 to 18 in (30 to 45 cm).
• Water: About 1 in per week (25 mm) including rain, more in heat on sandy soils.

Start seeds like a pro

Sow indoors 8 to 12 weeks before your last spring frost, about 0.25 in deep (6 mm), at 65 to 75 F (18 to 24 C). I use open flats and slice seedlings into clumps at transplant time.

Leeks handle crowding early, so I seed thick to save space. Bottom water to keep stems clean and reduce damping-off.

Transplant timing and prep

Move them out when plants are pencil-thick and 6 to 8 in tall (15 to 20 cm), usually 2 to 3 weeks before last frost in spring or late summer for fall crops. Harden off for a week and keep them slightly on the dry side so they don’t flop in wind.

Before planting, I trim roots to 1 in (2.5 cm) and tops to 6 in (15 cm). This makes dibbling easier and reduces transplant shock.

Soil that feeds, drains, and stays loose

Leeks crave deep, friable soil with high organic matter and steady nitrogen. I work in 1 to 2 in (2.5 to 5 cm) of finished compost plus a balanced organic fertilizer at label rate.

If your soil runs acidic, lime ahead of time to hit pH 6.2 to 6.8. A simple soil test pays for itself fast.

Planting methods that make long white shanks

I plant into 6 to 8 in deep trenches (15 to 20 cm), spacing plants 6 to 8 in apart. Use a dibber to poke holes, drop seedlings in, then water the holes so soil slumps around stems without burying leaves.

As plants grow, pull soil or mulch into the trench to blanch the shanks. Collars made from slit paper tubes work too and keep grit out.

Feeding and watering for steady growth

Leeks respond to a light monthly side-dress of nitrogen, like blood meal or fish hydrolysate, during peak growth. I mulch with straw to lock in moisture and keep soil cool.

Hit the 1 in per week water mark (25 mm). In heat waves above 90 F (32 C), I add an extra deep soak to prevent pithy stems.

Blanching techniques compared

• Soil hilling: Cheapest, gives the longest white shanks, slightly grittier if you rush washing.
• Paper or plastic collars: Cleanest harvests, great for wet autumns, shorter blanch length than heavy hilling.
• Deep trench only: Less labor later, solid results, my pick for big plantings.

Cold hardiness and timing by season

Spring-planted leeks carry you into fall, then shrug off light freezes. Overwintering types hold through deep cold with mulch and wind protection.

I plan two sowings: late winter for summer-fall eating, and midsummer for winter harvests. Hardy cultivars keep flavor sweet after frost.

“Leeks are exceptionally hardy and can stand in the ground over winter” — Royal Horticultural Society. I bank straw on mine when nights hit 10 F (-12 C).

Harvest and storage

Pull when shanks reach 1 to 1.5 in thick (2.5 to 4 cm), or earlier for baby leeks. I loosen with a fork to avoid snapping roots.

In the fridge at 32 F (0 C) and very high humidity, leeks store several weeks. USDA postharvest guidance notes best keeping near 95 to 100 percent relative humidity.

Flavor notes from the field

Cool nights concentrate sugars and give silkier texture. Heat can push a faint bitterness, which eases with steady water and mulch.

I taste a leaf now and then and adjust water or nitrogen. The plant tells you before the calendar does.

Top varieties I rate highly

• Bandit: Very hardy, stocky shanks, superb winter keeper.
• Tadorna: Reliable, upright habit, easy to clean at harvest.
• Bleu de Solaise: Blue foliage, stellar flavor after frost, photogenic rows.
• King Richard: Fast and tall for early harvests, less hardy, pristine white shafts.
• Porbella: Uniform and tidy, great for market bundles.
• Musselburgh: Classic heirloom, forgiving in mixed soils.
• Below Zero or Northern Lights types: Bred for serious cold, slow to bolt in spring.

Common problems and fixes

• Onion thrips: Silvery streaks and clubby leaves. Use reflective mulch, reduce dusty overhead watering, and apply spinosad or insecticidal soap in the evening.
• Leek moth and allium leaf miner: Time your floating row cover right after transplanting and seal edges well. Remove and destroy mined leaves.
• Rust (Puccinia): Orange pustules on leaves in late season humidity. Space well, water at soil level, and choose tolerant varieties.
• White rot: Patchy collapse with fuzzy white mycelium and black sclerotia. Pull and bin affected plants, rotate away from alliums for 4 to 8 years.

My field notes on spacing and yield

For fat, plate-ready shanks, I use 6 in spacing (15 cm); for baby leeks, I crowd at 3 to 4 in (8 to 10 cm). Tighter spacing means more pieces, wider spacing means bigger singles.

A 10 ft row (3 m) gives plenty for a household all winter. I replant that row every two weeks in spring for a long picking window.

Organic nutrition plan that works

Pre-plant: compost plus an organic base fertilizer. In-season: two to three light side-dressings at 4 to 6 week intervals and a kelp drench before heat spells.

If growth stalls midseason, a soluble fish feed perks leaves in three days. Overfeeding can split shanks, so I go light and steady.

Container and small-space tips

Use a 10 to 12 in deep box (25 to 30 cm) and a peat-free mix cut with 20 percent compost and 10 percent sand. Plant tight and collar early since you cannot hill much in pots.

Mulch with fine bark to keep media cool. Water daily in high summer and feed every 14 days with a half-strength liquid feed.

Regrowing grocery leeks

You can root the basal plate in water, then pot into soil for greens and small shanks. It buys a few weeks of harvest but lacks the vigor of seed-grown plants.

For dependable results, start from seed or high-quality plugs. Grocery leeks were bred for uniform shelf produce, not transplant resilience.

Companions and rotation

I pair leeks with carrots and beets, and I avoid beds that housed onions or garlic last year. Alliums share pests and diseases, so rotate 3 to 4 years if you can.

Short lettuce between rows pays rent early, then vacates before hilling. Low, quick crops keep soil shaded and moist for the leeks.

Soil moisture hack in heat

I run a drip line at 0.5 gph emitters (2 lph) every 12 in. A two-hour soak twice weekly holds moisture in the root zone and keeps leaves cleaner than overhead sprays.

On sand, I add biochar pre-season for better water holding. It pairs nicely with compost and does not sour the pH if you buffer it first.

What to buy: tools and supplies that actually help

• Dibbler with a 1 to 1.5 in tip (2.5 to 4 cm) for clean, deep holes in trench bottoms.
• Floating row cover at 0.5 oz fabric for pest exclusion without heat stress.
• Soil test kit that reports pH and nitrate. Calibrate your feeding to data, not vibes.
• Paper collar sleeves or slit tubes for fast blanching in tight beds.
• LED seed-starting lights with a simple timer. Leeks do fine at 200 to 300 PPFD.

Commercial questions gardeners ask

• Seed or plugs: Plugs cost more but shave 8 to 10 weeks of indoor work and give uniform rows for market harvest.
• Organic vs conventional seed: I see stronger seedling vigor in fresh lots regardless of certification. Check the pack date.
• Fertilizer label to watch: Look for slow-release N in the 4 to 6 percent range for base feeding, then supplement as needed.
• Mulch options: Clean straw is easiest to rake back at harvest; leaf mold can stick grit in tight sheaths if applied late.

Season extension tricks

In cold snaps below 10 F (-12 C), I hoop and cover, then bury the edges with soil. I harvest through snow with a narrow trench cut to the row.

In long wet spells, collars beat hilling because they shed grit. Clean leeks sell faster and wash quicker.

Leeks vs onions vs scallions

• Leeks: Long season, cold hardy, mild sweetness, white shaft prized for cooking.
• Bulbing onions: Shorter season options exist, less cold tolerant in ground, storage king if cured right.
• Scallions: Fast, compact, repeat sow every 2 to 3 weeks, best for stir-fries and raw crunch.

Reliable facts worth quoting

“Aim for 1 inch of water per week” is the standard recommendation from multiple U.S. extension services for leeks and onions, adjusted for rainfall and soil type.

USDA postharvest guidance recommends 32 F (0 C) and 95 to 100 percent relative humidity for storing leafy alliums like leeks for the longest life.

The Royal Horticultural Society notes that hardy leek cultivars can remain in the ground through winter and improve in flavor after frosts.

Two-sentence troubleshooting

Browning leaf tips usually point to drought or salt buildup, so flush the bed and resume deep, less frequent watering. Pale growth with lush leaves and skinny shanks suggests too little light or too much nitrogen too early.

Bulbous bases and early seed stalks show heat or daylength stress, which hits early varieties in late spring. Switch to overwintering types and sow later.

Anecdotes from rough seasons

One hot year I laid a 1 in layer of compost as a midseason blanket and the leeks stayed sweet through August at 95 F (35 C). Another fall a dusting of wood ash after rain kick-started growth on a tired bed and raised pH just enough.

I have pulled leeks from frozen soil with a digging bar, boiled them with potatoes, and thanked past me for trenching deep. That flavor after frost carries a whisper of the field.

Growing leeks isn’t fussy—just patience, attention, and a bit of dirt under your nails. Start with rich, loose soil and keep those young shoots well-watered. Trenching and mulching give you those long, white stems chefs dream of. Feed them a little, weed them often, and don’t forget to blanch if you want the sweetest flavor. Harvest when the stems are thick and sturdy—don’t wait too long, or the taste gets tough. Growing leeks rewards you with a harvest that brings slow-cooked stews and crisp autumn air straight to your table. Looking for other crops to add to your beds? Try garlic or chives—they’re classic companions, and just as easy to grow.