The Simple Way I Always Protect Winter Brassicas and Preserve My Kale and Cabbage Harvests

Winter brassicas are hardy, but that doesn’t mean plunging temperatures and hungry pests don’t trouble them during the colder months. The simplest way to protect winter brassicas and preserve your harvest is to cover the plants.

Kale, winter cabbages, cauliflower, and Brussels sprouts can survive winter in the vegetable garden and provide a bounty of crops for hearty seasonal meals. They even taste sweeter after a frost, but tough winter weather can harm them. They're also a target for hungry birds in winter, and pests such as slugs and snails can still be an issue.

To avoid losing any harvests, keep using physical barriers like netting when overwintering vegetables. They let light and moisture through but keep pests out. As a professional kitchen gardener, I routinely used covers like this ultrafine mesh netting at Walmart over my winter brassicas for many years to keep the harvests coming. I have also always staked taller brassicas to stop them from falling in strong winter weather.

Do You Need to Fleece Winter Brassicas?

Winter brassicas are tough crops that can overwinter outdoors without an issue. They have evolved to handle cold weather and freezes, including extended hard frosts.

For example, the hardiest kales can handle temperatures down to -10°F, and savoy winter cabbages and sprouts can tolerate down to around 10°F. The exact hardiness depends on the specific variety, and while the plants can tolerate those temperatures, they may suffer some damage, which affects the harvest.

Growers in USDA hardiness zone 5 are usually able to overwinter these crops without worrying too much about potential damage. However, in zones 3 or 4, you need to pick the hardiest varieties and consider covering them with thick-grade frost cloth, like this 2.0 oz thick frost cloth at Amazon.

In cold, northern climates, a thick layer of snow actually insulates plants. It does make harvesting vegetables trickier, but it can help protect vegetables from frost over winter.

Netting Winter Brassicas

Over winter, vegetables become targets for hungry wildlife, particularly birds, who like to graze on crops. Canada geese, pigeons, goldfinches, and more can do damage ranging from pecking holes in leaves to stripping whole plants.

Birds are the worst culprits over winter, but winter backyard pests like rodents, deer, and rabbits will also eat winter brassicas if given the opportunity. Slugs and snails are also active in winter and will nibble holes in leaves.

The simplest way to combat birds and protect winter brassicas from damage is to keep them covered with a physical barrier, namely bird-proof netting. The garden netting will allow essential light and water to reach your brassicas, but will, of course, stop the birds from getting at the plants and ruining your winter crop.

Typical bird netting has a mesh size of half to three-quarters of an inch. You can get heavy-duty bird netting with ¾ inch mesh at Amazon that can cover crops and stop birds, squirrels, deer, or rabbits from eating your crops.

If, like me, you use fine netting to stop caterpillars and other pests in a vegetable garden during summer, particularly cabbage worms and cabbage loppers, this netting can be left in place for winter and will provide perfect protection against cold-season pests. A good example of such a product is this insect barrier netting at The Home Depot, which also comes with 10 pegs.

Any netting needs to be put over a set of hoops or posts, rather than just laid directly over the top of the vegetables. You can get a hoop kit at Amazon that is easy to install and perfect for holding netting.

If you put the netting directly on the crops, birds or other pests can nibble the leaves through the material, unless you use the smallest mesh size. On frosty nights, the netting can also freeze directly to the vegetables and damage them.

Drape the netting over hoops or posts and secure the sides down with landscape staples (available at Lowe’s) or bricks. This guarantees birds don’t get underneath the netting, or the material doesn’t blow away in high winds and uncover a brassica buffet for local wildlife to enjoy.

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Staking Winter Brassicas

Tall winter brassicas, including Brussels sprouts, broccolini, and some types of kale, are vulnerable in strong winter winds. They can suffer wind rock if left to sway back and forth in the wind, which loosens and damages the roots. In a worst-case scenario, the plants can be completely toppled.

To support these winter brassicas and avoid losing any harvests, I opt to stake them with bamboo or wooden stakes, like this bundle of 25 garden stakes at The Home Depot. Tie the main stem to the stake with soft, flexible plant ties. I like these VELCRO plant ties at Walmart as they are strong, soft, adjustable, and reusable.

If you still have root vegetables in the ground, such as carrots, parsnips, celeriac, or rutabaga, you can easily overwinter them to keep the harvests coming through the winter.

You can overwinter root vegetables by covering them with frost cloth put over hoops to create a protective tunnel. Alternatively, I often put a thick layer of straw over the top of the crops to insulate the soil and make it easier to lift them when harvesting over winter.

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