All About Leeks

A popular and inexpensive staple in Mediterranean kitchens, the leek offers flexibility for creating both simple and elegant meals. Known in France as “poor man’s asparagus,” leeks have a classic role as a stock and soup enhancer but also can add flair as a garnish and star as a featured ingredient. Leeks have a unique flavor, texture and gelling quality that can be central to the success of a dish, making them preferable to onions, shallots or scallions in certain recipes.

Nutritionally Speaking

Despite their white-green appearance, leeks are characterized as a dark green vegetable. The greener sheaths contain a more concentrated number of flavonoids such as kaempferol. Some research links kaempferol with reduced risks of developing cardiovascular disease and cancer.

A 1-cup serving of raw leeks is an excellent source of vitamin K, and a good source of folate, iron, and vitamins B6 and C. Like other green vegetables, leeks contain carotenoids including lutein, which is linked to healthy eyesight and protecting cells from free radicals. Like onions, leeks have sulphur-containing amino acids that contribute “meaty,” savory flavors to dishes.

Growing

Leeks prefer sun and soil with consistent moisture. Leeks also require lots of nitrogen to thrive, so mixing in compost to the soil prior to planting is key. Due to their shallow root system, proper and regular watering is critical. Leeks tolerate cold well, so they can be harvested after the first frosts.

Availability

Available year-round, leeks have seasonal peaks in summer and winter. Wild leeks, or ramps, are available primarily in April and have an intense, garlicky flavor, but they are a different species than cultivated leeks.

Purchasing

When purchasing leeks, look for a white base, firm stalk and supple, smooth green leaves. Large leeks with more dense fibers require more time to cook, so select similar-sized leeks for consistent cooking.

Storing

Unlike onions and garlic, leeks require refrigeration for storage. Untrimmed and unwashed leeks can be stored in the refrigerator for up to two weeks; cooked leeks should be eaten within a couple of days.

Preparing

While an onion’s flavor is found in the bulb of the plant, leeks’ flavor is in the thick stems that are reminiscent of giant scallions, so they require some effort to clean. Leeks are known as “dirty” vegetables due to trenching, a technique for piling soil around the base of the stalk to blanch it white, which then traps grit between layers as the stalk grows.

To clean a leek, remove roots and tough outer leaves, then cut the stalk in half lengthwise and run water through the layers.

Using

Leeks often are used more for their tender, sweeter white sections than for their leafy greens. Heat quickly turns leeks silky, making them ideal in gratins, frittatas and soups such as vichyssoise. Leeks are a must in many French dishes. Stews, soups or stocks thicken when leeks are added as an ingredient or as a bouquet garni  flavor bundle (leek leaves wrapped around thyme, parsley and bay leaves.) When cooked, leeks develop a slippery texture that gels when cooled, adding body to liquids.

Other ways to cook leeks include slicing them into strips to pan fry or sauté for a crispy garnish on soup, pizza or fish; charring or grilling whole leeks to serve halved and stuffed; or braising them for tender centers with crispy edges.

Mince the tender white base of leeks to make a sweeter and more subtle replacement for shallots in a vinaigrette. Cabbage-like flavors may be perceived in the greener sections and inner stalk where the strongest flavors are concentrated.

This information originally appeared in Food & Nutrition Magazine^®, published by the Academy of Nutrition and Dietetics.