Leeks are a mild-flavored member of the allium family, prized for their succulent, edible white shank. Achieving a substantial harvest depends on correct planting depth and precise horizontal spacing. The initial arrangement influences the size of the mature vegetable and the ease of the blanching process. Proper distance between plants and rows is necessary for cultivating the long, white portion of the leek.
Preparing the Planting Environment
Successful leek growth requires preparing a deep, loose planting environment. Leeks thrive in well-draining soil that is rich in organic matter, ideally with a pH between 6.0 and 7.0. To support the long, straight shank, the soil should be worked to a depth of at least 10 to 12 inches.
The initial planting depth is a proactive measure for blanching the stem. Gardeners use one of two methods: digging a deep trench (4 to 6 inches deep) or dibbling. Dibbling uses a stick to create individual holes, about 5 to 6 inches deep, for each transplant.
When using the dibbling method, the leek seedling is dropped into the deep hole, and the hole is not filled with soil. Instead, the transplant is gently watered, which washes just enough soil around the roots to settle the plant. This technique immediately begins protecting the lower stem from sunlight, starting the development of the white shank.
Specific Dimensions for Planting Leek Seedlings
The horizontal distance between leek seedlings directly impacts their final size and later maintenance. For cultivating large, mature leeks, the optimal spacing is 6 inches between each plant within the row. This distance provides adequate space for the stem to thicken without competing excessively for nutrients.
The spacing between rows is equally important, as it must accommodate future maintenance tasks, particularly hilling. Rows should be spaced 12 to 18 inches apart, which allows enough room for the gardener to maneuver and draw soil up around the growing stems. Wider row spacing, sometimes up to 24 inches, can be beneficial if mechanical cultivation or extensive hilling is planned.
Gardeners wishing to harvest smaller “baby leeks” can adjust the spacing to 3 to 4 inches between plants. This closer proximity results in slender, tender stalks that mature more quickly. Adhering to the 6-inch spacing ensures each plant receives sufficient light, air circulation, and nutrients for robust growth.
Technique for Achieving the White Shank
The desirable white color and tender texture of the lower leek stem is achieved through blanching, which involves excluding light from that portion of the plant. This process capitalizes on the initial deep planting by continuing to bury the stem as the leek grows upward. The primary method for blanching is hilling, where soil is gradually mounded around the developing stalk.
Hilling prevents photosynthesis in the covered stem, stopping the production of chlorophyll and resulting in pale tissue. The process should begin once the leeks have established themselves and the stems are about the thickness of a pencil, typically reaching a height of 10 to 12 inches. Soil should be pulled up around the stem in small increments, generally 2 to 3 inches at a time, being careful not to bury the central growing leaves.
This mounding action should be repeated every few weeks throughout the growing season, a necessity that explains the need for wide row spacing. The cumulative effect of multiple hilling sessions is a long, straight column of blanched tissue, which forms the prized edible white shank. Following each hilling, a deep watering is beneficial, as it helps to settle the newly mounded soil and provides necessary moisture.