How to Grow Leeks: How to Plant and Harvest Leeks at Home

Leeks (a cultivar of Allium ampeloprasum) belong to the onion family of plants, making them similar to scallions, green onions, chives, and garlic but with a more mild and herbal flavor that sweetens as they cook. Leek plants have tough, flat, blue-green leaves that grow to encircle each other, creating a fan of folded leaves with white stems. Unlike other root vegetables, leeks do not usually form a bulb; the bottom few inches of a leek’s stalk are the edible portion of the plant.

Leeks can be biennial or perennial, with perennial leeks forming new bulbs, similar to shallots. Leeks thrive best if planted during cool months, typically in the early spring or fall. They have a growing period of about three months. After you harvest them, leeks can work well as an aromatic veggie in soups and casseroles.

You can grow leeks from seed or transplant young leeks into your garden. Here are factors to consider when planting, growing, and overwintering your leek plants so that they thrive year over year.

1. 1. Temperature: You can start leek seedlings indoors around eight to 12 weeks before the last frost in spring. Once temperatures are staying above 40 degrees, you can begin to harden off your leeks over the course of a week before completely transplanting the baby leeks, after they are about 10 weeks old. The hardening-off process gradually exposes your indoor plants to outside conditions, allowing them to slowly adjust through short stints outdoors, before transitioning them to your garden. Following this schedule, harvesting leeks should be possible in early summer. For an overwinter harvest, or winter or spring harvest, you can directly seed your leeks in the late summer which will allow for the warmth they need for germination.
2. 2. Diseases: You may come across blight or leek rust, a forming of orange pustules on the leaves. These usually develop in damp weather, so the best course of action is to remove the affected leaves and improve the air circulation around the leeks. Similarly, leaf rot—white spots on the tips of leaves—can appear in damp weather or soil that is too wet. Allow the soil to dry between waterings and remove any affected leaves.
3. 3. Pests: Slugs, onion maggots, leafminers, and thrips are all pests that pursue leeks. You can spray the plants lightly with neem oil, or another organic solvent, to get rid of these nuisances.
4. 4. Soil: To plant leeks, use a soil mixture that’s sandy, well-draining, and slightly acidic with a pH level between 6.0 and 7.0. Leeks may also tolerate more alkaline soils. Although they’re not heavy feeders, leeks require nutrient-dense soil. You can use a high-nitrogen fertilizer, compost mixture, composted manure, or another organic matter mid-season to improve your harvest.
5. 5. Spacing: Plant leek seeds at least six inches apart and about six to eight inches deep in the soil. Planting them deep will keep the white part of the stem—the edible part of the plant—from turning green as it grows.
6. 6. Sunlight: Leeks should receive around eight hours of bright, full sun daily throughout the growing season. Try to plant your leeks in the sunniest spot in your garden.
7. 7. Water: Since they have shallow root systems, leeks need frequent watering. A weekly watering should work for most environments, although in warmer climates you may need to water more often. Adding mulch can not only help retain water but also help to keep your garden weed-free.
8. 8. Weeds: Since leek roots are fibrous and shallow, you should be careful when weeding so you don’t accidentally damage the leek by hoeing too close to the plant. Mulching with either weed-free straw or herbicide-free grass clippings to a depth of three or four inches can help prevent weed growth.

The type of leek will determine the specific harvesting timeline. Most leek varieties’ growing season lasts 120–150 days, although there are some modern cultivars bred for shorter, 90-day seasons. Keep in mind that leek tops don’t die back like those of onions or shallots when it’s time to harvest them. To know it’s time to harvest your leeks, look for the base of your leeks to have at least a three-inch white section that feels firm and solid. Either twist and pull the leek out of the ground or dig the leek out to harvest it.

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