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Deep Winter Vegetable Production

high tunnel with raised beds of garden vegetables, a group of school children in the back corner

High tunnels are plastic-covered, solar greenhouses that can be used year-round for vegetable production. The low temperature and light of winter is a challenge for gardeners, but there is an opportunity to grow and market throughout the winter in many regions of West Virginia using high tunnels, which can be constructed and operated at a fraction of the cost of greenhouse production.

Root vegetables are able to be harvested or overwintered from October to April in high tunnels. Root vegetables grown in winter are very nutrient dense and have optimal sweetness from the cold growing conditions. They also adapt to the progressively lower temperatures and light during winter.

The goal should be to have a root crop that is close to maturity before late November when the day length decreases to less than 10 hours. If seeded before the middle of September, root vegetables are ready for harvest before early December. If the root crop is not mature by early December, the high tunnel can be used to overwinter the crop for harvest in early spring – with the exception of beets, as they do not overwinter well.

Leafy vegetables can also be grown throughout most of the winter in high tunnels. Kale, collards, spinach and chard are exceptionally cold tolerant and, like root vegetables, have a sweeter taste when grown in cold weather. Spinach continues to produce new leaves even in the coldest months of the year in a high tunnel. These leafy crops are seeded or transplanted in September and October for early winter harvest or for succession harvests starting in February. Some lettuce varieties tolerate cold temperatures and low light, and can be harvested in the high tunnel throughout the winter.

By Lewis Jett, WVU Extension Specialist – Commercial Horticulture