PLANTING INSTRUCTIONS

Growing leeks rewards gardeners with a versatile, mild-flavored member of the allium family that bridges the gap between onions and garlic. These elegant vegetables, with their long, cylindrical white stems and fan-like green tops, are prized in cuisines worldwide for their subtle, sweet onion flavor. Leeks are more cold-hardy than many garden vegetables, making them excellent for extended-season harvests. Though they require a long growing season, the patience invested in growing leeks pays off with their distinctive flavor and culinary versatility.

• Best Time to Plant: Leeks have a long growing season of 120 to 150 days and are cold-tolerant once established. For most regions, start seeds indoors 8 to 10 weeks before the last expected spring frost. Transplant seedlings outdoors 2 to 4 weeks before the last frost date when they are about pencil thickness. In mild-winter areas, leeks can also be sown in late summer for winter or early spring harvests. For a continuous supply, consider succession planting by starting new batches of seeds every 2 to 3 weeks during early spring.
• Soil Type: Leeks thrive in deep, fertile, well-draining soil with a pH between 6.0 and 7.0. Before planting, work the soil to a depth of at least 12 inches (30 cm) and incorporate 4 to 6 inches (10 to 15 cm) of compost or well-rotted manure. This ensures the loose, rich growing medium leeks need to develop their long, straight stems. Sandy loam is ideal, as it allows for the proper development of the edible white portion. Heavy clay soils should be amended with organic matter and sand to improve drainage and prevent rotting.
• Spacing: When transplanting seedlings, place them in trenches 6 inches (15 cm) deep and 8 inches (20 cm) wide. Space the plants 6 inches (15 cm) apart in rows that are 12 to 18 inches (30 to 45 cm) apart. As the plants grow, gradually fill in the trench with soil to blanch the stems, leaving just the upper portion of the leaves exposed. Alternatively, plant leeks in individual holes made with a dibber or the handle of a garden tool, about 6 inches (15 cm) deep, and water them in, allowing soil to naturally fill in around the stem as the plants grow.

CARE TIPS

• Watering: Leeks require consistent moisture throughout their long growing season to develop properly. Provide approximately 1 to 1.5 inches (2.5 to 3.8 cm) of water per week, adjusting based on rainfall and temperature. Deep, thorough watering is better than frequent shallow watering, as it encourages deeper root development. Water at the base of plants to keep foliage dry and reduce disease risk. A 2 to 3-inch (5 to 7.5 cm) layer of organic mulch around plants helps retain soil moisture, suppress weeds, and keep soil temperatures more consistent.
• Fertilizing: Leeks are moderate to heavy feeders that benefit from regular nutrient supplements throughout their long growing season. After the initial pre-planting soil enrichment, side-dress with a balanced organic fertilizer or compost when plants are about half-grown (approximately 2 months after transplanting). A nitrogen-rich organic fertilizer, such as blood meal or fish emulsion, can be beneficial for promoting leaf and stem growth. For extended-season leeks, apply an additional side-dressing in late summer to support continued development through the fall and winter months.
• Blanching: To increase the length of the white, tender portion of leeks (the most desirable part for culinary use), blanching is essential. As leeks grow, gradually mound soil around the developing stems, taking care not to allow soil to fall between the leaves. This process, called hilling, should be done every few weeks, adding 1 to 2 inches (2.5 to 5 cm) of soil each time until you’ve built up a 4 to 6-inch (10 to 15 cm) mound around the lower portion of each plant. Alternatively, wrap the lower stems with cardboard collars or use cardboard tubes to exclude light. Blanching not only increases the edible portion but also improves flavor by reducing bitterness.

HARVESTING

• When to Harvest: Leeks are typically ready for harvest 100 to 150 days after planting, depending on the variety and growing conditions. They can be harvested at any size once they reach a diameter of at least 1 inch (2.5 cm), but larger leeks with stems 1.5 to 2 inches (3.8 to 5 cm) in diameter offer more usable material. Unlike many vegetables, leeks can remain in the garden for extended periods, even through frosts, and be harvested as needed. In fact, exposure to light frost improves their flavor by converting starches to sugars. In mild winter areas, they can be harvested throughout the winter.
• How to Harvest: To harvest leeks, loosen the soil around the plant with a garden fork, being careful not to damage the roots or stem. Gently pull the entire plant from the ground, or if the soil is very compacted, use a garden fork to lift the plant. For deeply planted leeks, you may need to dig alongside the stem to free it completely. After harvesting, trim off the root end and remove any damaged outer leaves. Rinse thoroughly to remove soil that may be lodged between the leaf layers, especially near the base where the white stem transitions to green leaves. For storage, leave the foliage intact if storing in the refrigerator, or trim to 2 inches (5 cm) above the white portion for longer-term storage in cool, humid conditions.

TROUBLESHOOTING

• Common Issues: • Leek Rust: Orange-brown pustules on leaves, which may eventually turn yellow and die back. • Thrips: Tiny insects that cause silvery scarring and distorted growth on leaves. • Onion Maggots: Small, white larvae that feed on the developing bulbs and stems, causing wilting and rot. • Leek Moth: Caterpillars that tunnel into leaves and stems, creating whitish mines and holes.
• Solutions: • Leek Rust: Improve air circulation by ensuring proper spacing. Remove and destroy affected leaves promptly. Practice crop rotation, avoiding planting leeks where any alliums (onions, garlic, shallots) have grown in the past three years. For severe infections, apply a copper-based fungicide according to package directions. Choose rust-resistant varieties when available. • Thrips: Use reflective mulch to deter thrips from landing on plants. Introduce beneficial insects like predatory mites or pirate bugs. Apply insecticidal soap or neem oil, focusing on the base of the plants where thrips often hide. For severe infestations, consider organic insecticides containing spinosad. • Onion Maggots: Protect young plants with row covers to prevent adult flies from laying eggs at the base of plants. Practice crop rotation. Apply beneficial nematodes to the soil to control larvae. Remove and destroy any affected plants promptly to prevent spread. Consider using collars around the base of plants to create a physical barrier. • Leek Moth: Monitor plants regularly for signs of damage. Use floating row covers during the growing season to prevent adult moths from laying eggs on plants. For active infestations, apply Bacillus thuringiensis (Bt) according to package directions. Practice thorough garden cleanup in fall to remove overwintering pupae.