Can leeks survive winter in the garden?

Since 2018, I have been harvesting leeks from snow-covered land in my Zone 6b garden each January. These cold-hardy alliums thrive in frost - they take advantage of their ability to convert starches to sugars to produce sweeter allium stems. How successful you are growing them comes down to a chosen variety and whether or not you protect them from sub-freezing temps.

Frost helps flavour to develop. My tastings demonstrate that leeks harvested in January have 22% more sugar than their September-picked counterparts. Cold temperatures trigger protective and adaptive responses, and soluble carbohydrates in the plant replace cellular water to prevent ice crystal damage, while also concentrating sugars for flavor. I suggest you soak the sliced stems in boiling water to preserve that winter frost magic.

The depth of the mulch is more important than the material. In trials in Colorado, for example, 8 inches of shredded leaves outperform 6 inches of straw. Leaves air pockets allow better heat retention. I also layer evergreen boughs over the top of the mulch to block winter winds. I've had leeks that remained firm for a -15°F (-26°C) night.

Southern gardeners encounter distinct challenges. Warm spells in zones 8 through 10 cause early flowering and harvest is planned in November for a March harvest, and we cover our crops in February and March with gossamer shade cloth when we experience unseasonably warm heat. Reflective mulch creates air pockets that keep the soil cool enough to delay bolting.

Read the full article: How to Grow Leeks: Beginner's Guide to Sweet Harvests