Grow leeks in a sunny bed, start seeds on a schedule suited to your climate, and keep young plants weed-free and watered while they establish. For long white shanks, plant deeply or gradually earth soil around the stems; blanching is optional. Leeks take months to mature, but you can lift them at a useful size and harvest them one at a time.
Choose a site and leek variety
Leeks are biennials usually grown as annuals. Unlike onions, they form a thickened stem and leaf sheaths rather than a bulb. Give them full sun: University of Maryland Extension recommends at least six hours daily, with eight to ten hours preferred. Choose a variety for the season you want to harvest. Summer leeks are generally smaller and harvested in the year they are planted; overwintering types are typically harvested the following spring and may have a stronger flavor. Consider local hardiness, expected size, days to maturity, flavor, and disease resistance when choosing leek seeds. The University of Maryland Extension and the Royal Horticultural Society offer variety guidance for their respective regions.
When to sow and plant leeks
There is no single planting date that works everywhere. Leeks need a long growing season, and the right timing depends on your climate, variety, starting method, and whether a source counts maturity from sowing or transplanting. Maryland Extension gives a cultivar-dependent range of 70–120 days to maturity; the RHS describes a crop taking about six months. Treat these as regional guides, not directly interchangeable promises about your own harvest date.
Use your local calendar
- UK guidance: The RHS lists March and April as the main outdoor sowing months. May and June sowings can provide later winter or spring crops and baby leeks.
- Maryland guidance: Start seeds indoors for early spring transplants or later in summer for a fall crop. After hardening off, leeks can be planted several weeks before the last frost.
- Utah guidance: Utah State University Extension recommends sowing in late March or transplanting in April, and gives seedlings six to eight weeks of growth before transplanting.
These schedules reflect different regions; check your local extension service or gardening authority for timing suited to your growing season. Sources: RHS, University of Maryland Extension, and Utah State University Extension.
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Start seeds indoors or in a seedbed
You can raise seedlings indoors or sow them in a separate seedbed and move them later. A seedbed frees the main plot for faster crops while leeks are growing. Under RHS guidance, indoor-raised plants are typically ready to go outside at about eight weeks old and 20 cm (8 in) tall; harden them off before planting. If sowing dates or transplant readiness differ in your region, follow local guidance.
How to transplant leeks and space them
For an RHS-style planting, make holes about 15 cm (6 in) deep and 5 cm (2 in) wide. Put one leek in each hole, space standard plants 15–20 cm (6–8 in) apart, and leave about 30 cm (1 ft) between rows. Water to settle each plant in, but do not backfill the hole. The open hole and deep planting help produce a longer white shank. A dibber can make the holes, but a suitable trowel handle or other tool can work too.
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For smaller baby leeks, the RHS suggests 10 cm (4 in) between plants. University of Maryland Extension instead gives a simpler five-inch spacing. These are different regional recommendations; choose one system suited to your conditions rather than combining measurements indiscriminately. Sources: RHS and University of Maryland Extension.
Care for leeks as they grow
Weed and water
Keep the bed weed-free, especially while plants are young: leek foliage casts little shade, so weeds can compete for space and resources. Water seedlings until established, then water during prolonged dry spells. Leeks in containers need more regular watering than those growing in the ground. Avoid wetting the foliage when practical, as the RHS notes that wet leaves can encourage leek rust. Adjust watering to soil and weather rather than treating a schedule from another region as universal. Sources: RHS and Utah State University Extension.
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How to get longer white stems
Light reaching the lower stem keeps it green. Deep planting and gradually drawing soil around the plant as it grows exclude light and lengthen the white shank. The RHS advises earthing up several times, taking care not to let soil fall between the leaves. Blanching is optional: Maryland Extension notes that hilling can make stems more tender and mild, but it is not essential for an edible crop.
Winter and pests
Established leeks are hardy and can stand winter conditions, according to the RHS. Where insect damage is a concern, insect-proof mesh is one option; Maryland Extension identifies allium leafminer as a leek pest. Check local extension advice for identification and control appropriate to your area.
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When and how to harvest leeks
Harvest leeks whenever they reach a size you can use. Under RHS guidance, baby leeks may be ready after a couple of months, while full-sized plants can take around six months. Gently loosen each plant with a fork and lift it from the soil. Harvesting alternate plants gives the remaining leeks more room to grow larger. Suitable late varieties can stay in the ground through winter and into spring, ready to lift as needed. Frost may sweeten flavor, but the effect is not guaranteed for every variety or location. Maryland Extension separately gives a cultivar-dependent maturity range of 70–120 days; the growing method and starting point for counting affect how that estimate fits a gardener’s calendar. Sources: RHS and University of Maryland Extension.
Quick Recap
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- Variety Information: Carantan Leek with Botanical Name Allium porrum, classified as Heirloom Type for traditional gardening
- Mature Plant Dimensions: Grows to 8.5 inches long and 2 inches wide with a maturity period of 110 days from planting
- Growing Requirements: Requires full sun exposure during warm season planting with indoor sowing method recommended
- Planting Specifications: Plant seeds at 1/2 inch depth with spacing of 8 to 10 inches between plants
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