Leek
Allium porrum
Amaryllidaceae · onion family
- Matures
- 120–150 days
- Harvest
- Once · Annual
- Sun
- 4–8+ hrs
- Spacing
- 2–4 in
Planting window
When to sow, by microclimate — foggier blocks run a different calendar than sunnier ones.
| Jan | Feb | Mar | Apr | May | Jun | |
|---|---|---|---|---|---|---|
| Foggy | ● | ● | ● | ● | ||
| Sunny | ● | ● | ● |
| Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|
| Foggy | ||||||
| Sunny |
Sunlight
How well it does at each level of direct sun per day.
Soil depth
Root room it needs — useful for sizing raised beds and containers.
Spacing
Room each plant needs — along the row and between rows — for sizing beds.
- In-row
- 2–4 in
- Between rows
- 18 in
Growth habit
The shape it makes in the bed and how tall it gets — what tells you whether to give it a trellis, a stake, or just room.
- Habit
- Upright
- Mature height
- 2–3 ft
Stands on its own; the tallest types appreciate a stake in wind.
How to start it
Sow it where it grows, or raise it under cover and set it out — and how far ahead to start the seedlings if it's the latter.
- Usually
- Transplant
- Start indoors
- 10–12 weeks ahead
Started under cover, then set out as a seedling.
Getting started
How it goes in the ground — how deep to sow or set it, and the soil temperature it needs to wake up. The cold-soil floor is the real limiter for direct-sowing in a foggy SF spring.
- Started from
- From seed
- Ideal soil temp
- 65–85°F
- Sow depth
- 0.25 in
- Time to emerge
- 5–7 days
Germinates between 32–95°F; happiest around 65–85°F.
Pests & diseases
What tends to trouble this crop — what it is, what you'll see, and what to do about it, least-toxic first.
Pests3
Thrips
- What it is
- Most adult thrips are elongate, slender, minute (less than 1/20 inch long), and have long fringes on the margins of both pairs of their long, narrow wings. Immatures (called larvae or nymphs) are oblong or slender and elongate and lack wings.
- What you'll see
- Thrips feeding on plants can damage fruit, leaves, and shoots and very noticeably affect plants’ cosmetic appearance. However, thrips rarely kill or threaten the survival of trees and shrubs.
- What to do
- Thrips species that feed on many different plant species often move into gardens and landscapes when plants in weedy areas or grasslands begin to dry in spring or summer. Avoid planting susceptible plants next to these areas, and control nearby weeds that are alternate hosts of pest thrips.
Onion Maggot
- What you'll see
- White worm that feeds on seedlings, roots or bulbs.
- What to do
- Use crop rotation, avoid excessive amounts of organic matter, and apply insecticides at planting if maggots have been a problem in the past. Destroy infected plants.
Wireworm
- What you'll see
- Larvae of click beetle. Dark brown to yellowish, jointed hard-shelled and cylindrical. Feeds on roots, seeds, and underground stems.
- What to do
- Use crop rotation, avoid excessive amounts of organic matter, and apply appropriate insecticide at planting if a problem in the past. Rotenone or wood ashes also provide some control.
Sources
Every figure above is backed by these.
- UC Master Gardeners, San Mateo–SF Countiesbacks plantingWindow, startMethod · Foggy & Sunny calendars, Leek row: seed/transplant Jan-Apr (foggy), transplant Feb-Apr (sunny). Start method: Foggy & Sunny calendars, Leek row: (T) transplant in both, with (S) sow seed additionally listed in the Foggy calendar.
- Golden Gate Gardening (Pam Peirce)backs sunlight, lifecycle, harvestStyle · Leek is a full-sun allium that tolerates light shade. Habit and harvest: annual, once — from this source's entry for this crop.
- UC Master Gardeners, Sonoma County (Planting Summary)backs daysToMaturity, inRowSpacing, rowSpacing, startMethod · Vegetable Planting Summary, Leeks row: 120-150 days, 2-4 in in-row spacing. Between-row spacing 18 in (Leeks row). Start method: Vegetable Planting Summary, Leeks row: method T (usually transplanted).
- Utah State University Extensionbacks soilDepth · 'How to Grow Leeks in Your Garden' (USU Extension): 'rooting depth in leeks is shallow' — shallow-rooted.
- UC Master Gardeners, Sacramento County (Germination)backs germination · GN 154 leeks row: 32/65–85/95°F (soil temperature).
- Cornell University Home Gardeningbacks germination · Cornell Home Gardening, Leeks guide — Days to emergence: 5 to 7
- USDA GRIN Taxonomybacks botany · GRIN accepts Allium porrum; other treatments place leek within A. ampeloprasum.
- Colorado State University Extension (Master Gardener)backs plantingDepth · Table 1 Cool Season, Leeks row: 1/4 in.
- University of Minnesota Extensionbacks growthHabit · 'Growing leeks': 'Plants grow two to three feet tall, and can have a width of two inches.' (24-36 in) — tall, self-supporting upright column of sheathed leaves, so classified upright.
- UC Master Gardeners, Santa Clara Countybacks startMethod · Start method: Planting chart: Leeks carry a Transplant row only; From seed to transplant 10-12 weeks.