10 Essential Steps for Growing Leeks

Learning how to grow leeks gives you another mild-tasting vegetable that's delicious in soupy stews and fresh salads. For many of the dishes you prepare, leeks make an excellent substitute for onions. You will appreciate their cold hardiness as well. Where many plants wilt, the leek survives frost.

Expect five or six months from planting, but this will repay you with a lengthened supply, as you may begin to gather them in nearly all states by the latter end of summer and continue until spring. This treatise offers clear and distinct guidance for success in cultivation, suitable for both beginners and experienced growers.

Ideal Climate and Soil Setup

Leeks thrive within specific temperature ranges, with the optimal temperature being 13° to 24°C. (55° to 75°F.) During the growing period, hardy kinds withstand temperatures as low as 6° C. (20° F.) in winter; when it drops below 4° C. (25° F.), they should be covered; a frost blanket will suffice.

Soil preparation makes a big difference for your leeks. They require well-drained soil that is high in organic matter. Test your soil's pH level before planting. If your soil pH is below 6.0, apply lime at a rate of 3-5 t/ha (1.3-2.2 tons/acre) to raise the pH into the required range of 6.0-7.5. If the pH is correct, then nutrients will be available to your plants.

Your crop depends on enough sunlight. Leeks require at least 8 hours of full sun per day, or at least half a day of direct sunlight, to develop thick stems. Full shade will significantly reduce your yield. Plant with care, knowing that some buildings and trees will come to obscure the sun from the plants down below. In fact, you will sometimes find a southern exposure of the garden most suitable in a northern exposure.

Planting and Spacing Techniques

When it comes to planting leeks, the particulars begin with determining the depth to plant your seeds. For sowing seeds indoors, plant ¼ inch (0.6 cm) deep in trays. For directly sowing in the garden beds, go slightly deeper at 1 cm (0.4 inch). This seed depth protects them from pests while allowing the sprouts to penetrate the soil with little effort. Starting leeks indoors gives you a head start, especially in colder areas.

Transplant the seedlings when they are as thick as a pencil, about ¼ in. (0.6 cm.) in diameter; their strong roots can readily recognize them. For each burial, prepare holes with a dibber about 9 in. (23 cm.) deep, since the more blanched the stems are, the better they will be. The soil will naturally settle around them.

Spacing depends on your garden method and which variety you're growing. If growing for open ground cropping in standard gardens, space plants 6-8 inches (15-20cm) apart each way. For 'Scotland' or any very small varieties, planted very intensively, space them 2-4 inches (5-10cm) apart. The closer the plants are, the heavier the crop will be for a given area of ground, but this will require close attention to the soil's nutrient content.

Watering, Feeding, and Blanching

Water the leeks two to three times a week to keep the soil evenly moist, but never allow it to become soaking wet, especially in sandy soils that require more frequent watering than clay soils. Strive for about 1 inch (2.5 cm) of rain per week. If you can install a drip irrigation system, your leeks will appreciate the extra care, and you will waste less water while avoiding the harm caused by wet leaves.

Feed your plants with balanced fertilizer before planting. Apply 150-200 kg/ha (130-175 lb/acre) of NPK fertilizer. When the leaves turn yellow mid-season, use a nitrogen side dressing of 30 kg/ha (26 lb/acre). Stop fertilizing six weeks before harvest.

Start blanching when the stems are at least 6 inches (15.2 cm) tall and continue every couple of weeks for the whitest stems. For standard gardens, use soil hilling, gradually mounding more earth around the stems. For container gardens, opt for collar techniques made of cardboard tubes.

Pest Control and Disease Prevention

Keep an eye out for undesirables such as: onion maggots that burrow into stems causing them to collapse; thrips that produce silver speckling on leaves, and leek moths that tunnel through and leave brown trails in the foliage. Control these pests by inspecting your plants on a weekly basis.

Organic controls such as neem oil at 2% concentration, every seven days for thrips. Row covers in spring and fall to prevent maggots from reaching the harvest, Bacillus thuringiensis for caterpillars.

Prevent diseases through spacing. Ensure plants have sufficient space to grow; generally, crops should be spaced at least 6-8 inches apart. This will help reduce humidity, a key factor in preventing fungal diseases. Rotate crops annually away from allium (onion) beds, and destroy weeds that harbor pests and diseases.

Check beneath the leaves weekly for eggs and larvae, especially during the early part of the fourth season. Record sightings of pest items, likely small larvae and eggs, as they appear to track down movement. Well-cultivated plants seem to avert most potential problems. Good air movement through the leaves and the dryness of the leaves essentially help maintain most fungal problems at bay.

Harvesting and Storage Methods

Harvest leeks when the stems reach a diameter of 1 inch (2.5 cm) or more after 5-6 months of growth, which indicates they are at maturity and are not yet old enough to become woody. The diameter should be measured at the soil line. Harvesting can progress until the ground is covered with frost in cold places. Pull gently to avoid breaking them.

Preserve Roots when Lifting. Push the fork in at a 45-degree angle. About 6 in. (15 cm.) from the plant to be lifted, insert a hand around the fork and gently twist and raise it, thus loosening the earth without stabbing the roots and allowing the stems to be lifted without bruising or breaking.

Trim roots to 1 inch (2.5 cm) and leave leaves on until ready to use, cutting them off 6 inches (15 cm) above the stem. Clean well by slicing down lengthwise and rinsing out all grit that is between the layers.

Store leeks at 32°F (0°C) with a relative humidity of 90 to 95%. This cold, moist environment will prevent leeks from shriveling and ensure they remain in perfect condition for several months. Store them in the refrigerator in bags or boxes made of perforated paper. In a root cellar, pack the leeks in boxes in damp sand.

5 Common Myths

Conclusion

Leeks stand out as your champion in cold-weather crops. The tender shoots are a welcome addition to soups and stews, as well as a fresh ingredient in salads. At a time when everything else has died, leeks will give you their tender edible stalks. Enjoy having them year after year.

Remember three guiding rules, and you can hardly fail. Keep the ground moist, never wet, and blanched, for blanched stalks that are white and tender. Abate disease by spacing and rotation, and you will have truly monstrous Leeks that will stand where other things would curl up and die.

Post-harvest care protects your investment. Clean leeks in cold water to dislodge all dirt. For storage, keep them at temperatures above freezing and humidity as high as possible. If done right, they should remain delicious for months. Your winter meals will taste as fresh as just-harvested!

Experiment with various styles and approaches. Try Scottish types for the earliest crops, or giant varieties for immense stems. Use the myth-busting information in this guide. You happen to have a laboratory for delicious things in your own garden.

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