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When to plant leeks

Onion family, Allium porrum

Spacing
6″ apart
Per sq ft
9
To harvest
100–120 days
Frost
Hardy

Companion plants for leeks

What to grow next to leeks, what to keep away, and what is only tradition. Every pairing says how strong the evidence is.

Grow together 2

Helps, or shares the bed well.

  • Carrot Mixed Interplanting onions or leeks reduced carrot fly in some trials, but only with several onion rows per carrot row; a token onion does nothing.

    Carrot guide

  • Celery Practical Both like rich, moist soil and fit together in narrow rows.

    Celery guide

Tradition only 2

On many charts, with little or no evidence.

  • Bush bean Tradition Said to harm Onions and garlic are widely said to stunt beans. No study we know of shows this; it may be worth a trial in your own garden.

    Bush bean guide

  • Pole bean Tradition Said to harm Onions and garlic are widely said to stunt beans. No study we know of shows this; it may be worth a trial in your own garden.

    Pole bean guide

Studied Field or lab research shows an effect, at least under some conditions.
Mixed Some studies find an effect, others don’t, or it only works in a narrow way.
Practical Explained by light, space, timing, support or a shared pest or disease.
Tradition Widely repeated, but with little or no evidence behind it.

See every pairing side by side in the companion planting chart, or try them in a bed with the garden planner.

When to plant leeks by city

Start leeks indoors 10–12 weeks before your last frost, plant them out up to 2 weeks before your last frost. Here is what that means for 2027 in cities across the US, using each city’s average frost dates (NOAA 1991–2020). Pick the city with the climate most like yours, or enter your ZIP code above.

City Last frost Start indoors Plant out
Seattle, WA (9a) Mar 13 Dec 19 – Jan 2 Feb 27 – Mar 13
Portland, OR (8b) Feb 25 Dec 3–17 Feb 11–25
Sacramento, CA (9b) Jan 12 Oct 20 – Nov 3 Dec 29 – Jan 12
Phoenix, AZ (10a) Jan 5 Oct 13–27 Dec 22 – Jan 5
Salt Lake City, UT (7b) Mar 31 Jan 6–20 Mar 17–31
Denver, CO (6a) Apr 30 Feb 5–19 Apr 16–30
Dallas, TX (8b) Mar 2 Dec 8–22 Feb 16 – Mar 2
Minneapolis, MN (5a) Apr 23 Jan 29 – Feb 12 Apr 9–23
Kansas City, MO (6b) Apr 4 Jan 10–24 Mar 21 – Apr 4
Chicago, IL (6b) Apr 10 Jan 16–30 Mar 27 – Apr 10
Columbus, OH (6b) Apr 20 Jan 26 – Feb 9 Apr 6–20
Nashville, TN (7b) Apr 1 Jan 7–21 Mar 18 – Apr 1
Atlanta, GA (8a) Mar 24 Dec 30 – Jan 13 Mar 10–24
Raleigh, NC (8a) Mar 28 Jan 3–17 Mar 14–28
Philadelphia, PA (7b) Mar 30 Jan 5–19 Mar 16–30
Boston, MA (7a) Apr 4 Jan 10–24 Mar 21 – Apr 4

In frost-free parts of Florida, southern California and the Gulf Coast, timing is about heat instead: grow leeks from fall through winter.

Leek spacing

In a square-foot bed, plant 9 per square foot. In traditional rows, space plants about 6 inches apart with 18 inches between rows.

Plant in a deep hole and hill up for long white shanks.

One square foot planted with leeks, as drawn in the planner.

How to grow leeks

Leeks are slow but simple: they need a long season and a head start indoors, then little more than water and some hilling. They are among the hardiest vegetables, so many gardeners harvest them through late fall and into winter.

Sun and soil

Full sun and deep, fertile, well-drained soil that stays moist, pH about 6.0–7.0. Roots are shallow; water regularly so the soil never dries out.

Planting

  1. Start seeds indoors 10–12 weeks before the last frost, ¼–½ inch deep. Trim seedlings back to about 4 inches if they flop.
  2. Transplant from about 2 weeks before the last frost up to the frost date, when soil is at least 45°F and seedlings are pencil-thin.
  3. Make holes 6 inches deep with a dibble, drop one seedling into each, and fill the hole with water instead of soil; it fills in over time.
  4. Space plants 6 inches apart in rows 18 inches apart.

Care

  • Hill soil up around the stems 2–3 times during the season, a few inches at a time, for longer white shanks. Keep soil out of the leaf fans.
  • Side-dress with nitrogen in early summer and again in midsummer.
  • Mulch to hold moisture and smother weeds.

Harvest

Dig leeks once shanks are about 1 inch thick or larger, usually 100–120 days after transplanting. Loosen soil with a fork rather than pulling. Leeks tolerate hard frost; in milder areas, mulch them heavily and keep harvesting into winter.

Common problems

  • Thrips: Silvery streaks on leaves. Hose plants down and keep weeds under control.
  • Onion maggot: Rotate alliums and avoid fresh manure in the bed.
  • Allium leafminer: A newer pest in parts of the Northeast that tunnels into leaves and stems. Cover plants with row cover during its spring and fall egg-laying periods.
  • Grit in the leaves: Soil falls into the leaf layers when hilling. Hill gradually and split leeks lengthwise to rinse.

Varieties to try

  • 'American Flag' — reliable, hardy, thick stems
  • 'King Richard' — long, slender, early; less cold hardy
  • 'Giant Musselburgh' — heirloom, very hardy, thick shanks

Crop rotation

Leeks belong to the onion family (Amaryllidaceae). Onion maggot and white rot persist. Rotate for 3–4 years. Relatives that count as the same family for rotation: onion, garlic, chives, green onion.

Frequently asked questions

When should I plant leeks?
Start leeks indoors 10–12 weeks before your last frost, plant them out up to 2 weeks before your last frost. Type your ZIP code above for exact dates, or see the city table.
What grows well with leeks?
Good neighbors for leeks include carrot and celery. Each one is listed above with the reason and how strong the evidence is.
How far apart should I plant leeks?
In rows, space leeks about 6 inches apart with rows 18 inches apart. In a square-foot bed, plant 9 per square foot.
How long do leeks take to grow?
About 100–120 days from planting out transplants to first harvest, depending on the variety and the weather.
Can leeks handle frost?
Yes. Leeks handle frost well and are planted before the last frost in spring.

Sources

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Plan your beds

When to plant

What grows together