Leeks

Leeks have a nice delicate flavor, but they can get pretty pricey in the grocery store. Luckily for us, they are easy to grow!

Unlike other members of the Allium family, such as garlic and onions, leeks do not form bulbs underground. Instead, leeks grow an edible stem that can be up to 2 inches in diameter. Like garlic, the leaves are flat (onion leaves are tubes). Leeks are commonly paired with potatoes, but they can also be steamed, roasted, or baked to stand on their own.

Leeks (liz west) CC BY 2.0

Leek cultivars

There are two basic types of leeks. Short-season leeks are planted in spring and harvested in late summer and early fall. Hardy long-season leeks are also planted in spring, in the north, but not until late summer in warmer areas. These leeks are not ready for harvesting for at least 100 days, which means they are ready for use through winter.

How to grow leeks

Leeks are biennial plants that are grown as annuals. You can start leeks from seed or by replanting the white base of an existing leek. If you use the base of a leek purchased from the grocery store, be aware that you may be introducing destructive pathogens into your garden.

The base should be planted much deeper than you might expect: 4 to 6" deep. This is how part of the stem stays white, because it is blanched underground. Blanching means keeping certain parts of a plant white by blocking sunlight. 

If you use seeds, plant them 1/2" deep and 6" apart. If you start seeds indoors, be sure to harden them off before planting them in the ground or in tall containers outside. You can also buy seedlings from your local garden store, but they will need to be gently untangled from each other before replanting - they look like unmown grass in the pot. Seedlings should then be transplanted deeper into the soil than they were, up to where the green stems begin, for a longer, more drought resistant edible. Once the seedlings are as big around as a pencil, bank soil or mulch around each plant to continue blanching the base. 

Leeks prefer cooler temperatures, so fall and winter are the best time to grow leeks in areas with hot summers. Leeks enjoy full sun and well-drained soil, but the two components that make the biggest difference in growing leeks are water and nitrogen. Leeks are heavy feeders, so planting them near peas or beans will provide an extra boost of nitrogen early in the growing process, followed with aged compost. Leeks have shallow roots so regular watering is needed for plants to reach full size. Water stress will significantly reduce yields. The soil should be moistened to a depth of 18 inches every week. Mulching around plants can reduce weeds, add nutrients, and cut water needs.

Onion maggots, onion rust, aphids, thrips, and onion white rot are the most common problems encountered when growing leeks.