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Biennial Plant · zones 5–10 · 22 varieties

Leek

Allium ampeloprasum

Amaryllidaceae — the same plant family as onion, garlic, scallion, shallot and 1 more here. Relatives share pests and diseases, which is why rotation plans group by family.

Leek (Allium ampeloprasum) is a biennial plant for USDA zones 5–10. It wants full sun and pH 6–7 soil, with about 1 in of water weekly. It matures in about 100–150 days from sowing, or 90–120 days from setting out a transplant. Watch for onion maggot and rust. Below: its full sourced profile from 10 extension sources, plus a planting calendar timed to your frost dates.

Zones 5–10 — USDA USDA
Sun Full sun
Water Moderate
Matures 90–120 days — from transplantest from transplant
Mature size 2–3 ft
Spacing 4–6 in
Soil pH 6–7
Frost Hardy
When to plant leektypical · zone 6b
Your zone
…or your ZIP, for your real frost dates

Germinating
Seedlings
Establishing
Growing
Harvest

Typical dates for zone 6b — set your zone or ZIP for yours. This calendar assumes the crop is started indoors. Timing is a guide from the crop's sourced growth stages; confirm with your local frost dates and extension before you sow.

Growing leekevery fact says where it came from

What we will not put a number on

We do not give a feeding rate for this crop, and that is deliberate rather than a gap. The figures published by extension services are pounds of nitrogen per acre for a production field — they do not convert safely to a raised bed or a pot without knowing your soil test and your fertilizer's analysis, and guessing errs toward burning roots. It is also why every chart you find online disagrees with the next one.

We give watering as a depth per week rather than gallons per plant, because that is how it is actually measured and how the published figures are written. A gallons-per-plant number depends on your spacing, your soil and whether the plant is in a pot — so it would look more precise than it is.

Site & soil

Hardiness zones
5–10
Sun
Full sun
Soil pH
6–7
Soil texture
Loam, Well drained
Frost tolerance
Hardy

No published figure for the temperature frost starts to hurt it, the temperature that would kill it and a heat limit. We looked — where a number is missing here it is missing from the research, not skipped. The crop’s frost and heat tolerance above still applies.

The plant

Mature height
2–3 ft
Mature spread
1–2 ft
Growth rate
Moderateest
Spacing in row
4–6 in
Between rows
8–16 in
Planting depth
0.25–0.5 in
Container size
2–5 gal — low end is the minimum, high end is betterest
Support
Self-supportingest
Grown from
Direct sow, Transplant

Water & feeding

Water needs
Moderate
Water per week
1 in/wk
Critical water
Establishment, Vegetativeest
Feeding
Moderate

Timing & fruiting

Days to maturity
100–150 days from seed · 90–120 days from transplantest
Harvest cues
Stem reached harvest size

Planted again for autumn

Set plants out by
late Jul typical · zone 6b

90 days to maturity from setting a plant out — that is what our sources measure for this crop, so this is a date for planting out and not a sowing date, counted back from the first frost above. Not published for anywhere in particular: it is your own frost date and this crop's own figure, which is why it works wherever you are. A days-to-maturity figure is a catalog number for a good season rather than a promise, and a cold month moves it.

Edible parts per source: leaf, bulb.

What tends to go wrongmost-cited first
PestsOnion maggotThripsWirewormsAllium leafminerBulb mitesSlugs
DiseasesRustMildewLeaf spotRot

Compiled from the extensions cited below. Which ones actually show up depends on your region — your extension's local list is the last word.

Companionswhat to plant near leek
✓
CarrotsTrialed

Interplanted onions confused carrot rust fly in some trials and did nothing in others. Worth a try, not a bet.

✓
BeetsTraditional

Chart canon, both directions.

✓
Cabbage familyTraditional

Old chart pairing; both hold cool-season beds.

✓
LettuceTraditional

On the classic charts — lettuce's own row lists onions.

✓
TomatoTraditional

Chart canon says onions and garlic make good tomato neighbors. No trials to point at, no conflict either.

✕
BeansTraditional

The most consistent 'no' in companion planting. Unproven, unanimous.

✕
PeasTraditional

Same flag as beans — every chart agrees.

Companion pairings from university extensions; badge = how strong the evidence is.

⚠ Reported toxicityverbatim from cited sources

Different parts differ — the edible part is the leaf and bulb; the notes below flag other parts or preparations.

PeopleOxalic acid, Contact dermatitis

Petsdogs, cats, horses

Recorded exactly as the source states it — not medical or veterinary advice. If a person or animal may have eaten a toxic part, call Poison Control (1-800-222-1222) or your vet / the ASPCA line (888-426-4435).

All 22 varietiesthe ones with their own page are linked
Variety Type DaysColorDiseaseWhat it is known for
American Flag Heirloom 130
Autumn Giant Heirloom Fall 85
Autumn Mammoth Heirloom Fall 90–120
Bandit Overwintering 105 PURPLE_BLOTCH RUST
Below Zero F1 Overwintering 90–120 RUST
Bleu de Solaise Heirloom Overwintering 100 Green
Carentan Heirloom 95 MIgardener describes this astakes the cold
Comanche F1 Overwintering 105
Electra Overwintering 150
Giant Musselburgh Heirloom Overwintering 100
King Richard Summer Early 75
Lancelot Heirloom 90 Green PURPLE_BLOTCH RUST WHITE_TIP
Megaton F1 Overwintering 90
Pandora 90
Prizetaker Heirloom 110–135 Rohrer Seeds describes this astakes the cold
Runner 90–120 PURPLE_BLOTCH RUST WHITE_TIP
Siegfried Overwintering 120
Surfer F1 Overwintering 115 Green PURPLE_BLOTCH RUST
Tadorna Overwintering 100 ANGULAR_LEAF_SPOT LEAF_SPOT YELLOW_SPOT
Titan 110
Upton F1 90
Varna Summer Early 60
Sources10 cited · 9 organizations
  • ASPCA Animal Poison Control Center
  • Clemson Cooperative Extension, Home & Garden Information Center
  • Cornell University Home Gardening (Cornell Cooperative Extension)
  • Michigan State University Extension
  • NC State Extension
  • Penn State Extension
  • University of Maryland Extension
  • University of Minnesota Extension
  • Utah State University Extension

We compile bare facts from these university-extension and horticultural sources, never copied prose. 15 of the 20 values on this page carry a citation. The rest are marked est; hover one and it says why — either nobody publishes a figure we could point at, or a person set it and attached no source. Figures vary with climate and seed source; confirm with your local extension before you buy.

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