It might be cold outside, but winter is still a time for homegrown harvests. Hardy greens will grow during the colder months, and you can keep those harvests coming for longer by overwintering leafy greens under a row cover, cloche, or cold frame.
Hardy winter leafy greens such as spinach, collard greens, winter lettuce, Swiss chard, pak choi, mizuna, and mustards can all provide late harvests of nutritious, tasty leaves at a time when offerings from the vegetable garden can be a bit more limited. Even in milder climates, a few simple steps to overwinter leafy greens can ensure a fantastic harvest throughout December and January.
Where to Grow Winter Leafy Greens During December
Winter leafy greens can be grown outdoors during the colder months, but they also make fantastic vegetables to grow in a greenhouse in the fall.
If you aren’t fortunate enough to have a large greenhouse in your backyard, don’t worry, as there are many options available to cultivate them outside successfully.
These include growing them under cloches, covers, cold frames, or in a mini greenhouse, like this portable greenhouse on Wayfair.
1. Pick hardier varieties more suited to cold weather
To grow winter leafy greens successfully, selecting the right varieties is important. Among all the different vegetables, some varieties will be hardier than others. Being careful and choosing varieties that offer the greatest resilience to cold and frost will help to ensure you get the best harvests possible through winter.
To grow lettuce in winter, opt for hardy varieties that are known to tolerate cold temperatures, and, for many, there is a tell-tale hint in their name. The likes of ‘North Pole’, ‘Arctic King’, or any varieties with ‘Winter’ in their name tend to be the hardiest of the winter lettuces.
It is the same with spinach, as certain varieties withstand the worst of the winter weather better than others, including ‘Giant Winter’ and ‘Verdil’, and kale, as ‘Red Russian’ and ‘Dwarf Siberian’ are the hardiest of all the types.
Many oriental greens are also well-suited to growing through winter, including bok choy, mizuna, and tatsoi. These winter leafy greens are available in different leaf shapes and colors, and can be picked as cut-and-come-again vegetables to add spicier flavours even through the coldest months.
2. Mulch plants to protect the roots
There are many benefits to mulching a vegetable garden in the fall, including helping to overwinter leafy greens and other cold-hardy crops. Putting a thick mulching layer around the base of the winter leafy greens insulates the plant’s roots, protecting them against dropping temperatures, and retains moisture in the soil.
The best types of mulch for protecting vegetables over winter include compost, straw, or shredded leaves. The latter of which makes a great cost-effective fall mulching material if you’ve been busy collecting leaves in recent months. Apply a layer 3-4 inches thick and leave a small bare ring around the plant’s crown.
For an extra layer of protection and to keep straw or leaves in place over winter, you can add a low tunnel covered with frost cloth or netting. For example, a hoops kit like this at Amazon can be used to quickly construct a low hoop tunnel to support any material over your crops.
3. Protect plants with row covers
Row covers offer a simple way to protect vegetables from frost. These frost cloths, also known as horticultural fleece, are made of polyester or polypropylene. There are varying thicknesses available, and heavier grades of row covers can provide decent levels of insulation against cold weather, such as this frost cloth at Amazon.
As the material is breathable and permeable, it allows water, light, and air circulation to the plants, while providing a crucial few degrees of warmth. It is not exact, but lightweight row covers can provide 2ºF of frost protection and heavyweight ones up to 8ºF. They can provide just enough insulation to help plants survive cold, frost, snow, rain, and freezing winds.
When using row covers, they need to be weighed down, either with garden staples (you can get heavy-duty landscape staples at Walmart), bricks, or stones. This keeps them in place throughout the winter. Any time you remove them to harvest your greens, remember to put the cover and weights back in place.
4. Cover crops with cloches
Cloches have been used for centuries to cover plants. From historic ornate bell-shaped glass cloches to modern plastic ones, these tools protect plants from frost and can make attractive features in a winter garden.
You can still get eye-catching antique glass cloches, either bell or lantern-shaped, but nowadays most are plastic. Alternatively, you can use recycled plastic containers, sheets, or frost cloth as a DIY cloche replacement. The more lightweight materials will need anchoring to remain in place over winter, unlike sturdier glass cloches that can withstand the elements.
Cloches provide warmth and insulation to the leafy greens underneath them, as well as a physical barrier against any pests that may wish to nibble on them during winter. As well as covers for individual plants, you can get a cloche tunnel, like this one at Amazon, to protect rows of plants from frost or animals.
5. Grow greens under cold frames
A cold frame is an ideal protected place to grow winter leafy greens, especially fast-growing vegetables like winter lettuces, mustards, bok choy, and spinach.
A cold frame is a mini greenhouse with a wooden or plastic frame and plastic or glass windows on the sides and top.
You can either start plants off in a permanent cold frame or place a lightweight portable version over vegetables in situ. This wooden cold frame from Amazon is an example of a portable version, or you could opt to use a plastic mini greenhouse, such as this one at Walmart.
The cold frame traps warm air during the day and retains it into the evening when the lid is shut, keeping the greens insulated against dropping temperatures outside. When there are freezing temperatures, cold rain, or snow, you can keep the cold frame lid shut as a shield. On sunnier winter days, open the lid for air circulation around the plants.
Root vegetables are another fantastic crop for homegrown harvests throughout the winter. A selection of carrots, parsnips, rutabaga, celeriac, and Jerusalem artichoke can provide rich pickings for dinner plates in the colder months.
In milder climates, you can overwinter root vegetables in the garden by covering them with mulch or frost cloth to protect them from freezing. However, in cold regions, it is beneficial to lift and store them in crates filled with moist sand in a dark, frost-free place, such as a garage, cellar, or shed.
This folding knife has a stainless steel blade and a beech wood handle. It is perfect for harvesting leafy greens and other vegetables.
This growing kit features over 16,000 seeds for growing 35 different vegetables. All the seed packets are for non-GMO and heirloom varieties of crops.
This metal raised garden bed measures 36" H X 50" W X 27" D and comes with a plastic greenhouse cover to protect your vegetables.
