December may seem cold and unsuitable for planting to many gardeners, but for those who want to get their fix of seed sowing, there are options available. You may need to do it inside rather than out, but there are vegetables you can plant in December in a greenhouse, cold frame, under cloches, or on a bright windowsill.
There is no hiding that, in most hardiness zones, the weather is cold and light levels are lower in December. As warmth and light are two essential factors for good germination, it means you often need to supplement natural levels by using heat mats and grow lights during the depths of winter. Not all vegetables need this, but many do; it depends on your climate.
Yes, sowing and planting vegetables in December can be a bit trickier, but don’t let that stop you from trying. If you have space and some determination, there is no reason you can’t keep sowing throughout winter. I have grown vegetables year-round, supplying restaurants 52 weeks a year, and have chosen seven vegetables to plant in December to showcase. Winter sowings allow you to get ahead, enjoy earlier spring harvests, or even have quick crops during the lean winter months.
(Image credit: Jacky Hobbs / Future)
7 vegetables to plant in December
Before choosing vegetables to plant in December and starting sowings, consider your climate and conditions to ensure you have any necessary equipment.
Growers in colder climates may benefit from heat mats or heated propagators to provide extra warmth to seeds during winter, which aids germination. Once seedlings appear, grow lights help prevent leggy seedlings, a common ailment caused by a lack of light when growing indoors over winter.
Shop products to help winter sowings:
This seedling heat mat maintains temperatures of 68-86°F and has a digital thermostat so you can set a desired temperature.
This propagator comes with a heated base to maintain warm temperatures and a full-spectrum light.
This complete seed starting kit includes a tray with 40 seed cells, two LED grow lights, a heat mat, and a 3-in-1 moisture meter for precise watering.
1. Garlic
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Garlic bucks the trend, as it is one crop you can still plant outside this month, but this is the last chance to get fall-planting types of garlic into the ground. Garlic planting can be done in early December, as the crop needs cold exposure to develop bulbs.
To plant garlic outdoors, split your garlic bulbs into individual cloves. Plant each clove six inches apart, with the flat end down and pointed end up. The tip of the clove should be an inch below the soil surface.
If you do have a heavy soil type that sits waterlogged over winter, you can start growing garlic in pots. And this is a crop on this list that won’t require additional heat indoors, just a protected environment such as a cold frame or unheated greenhouse for winter.
Fill a pot at least six inches deep with a good potting mix for container gardening, and place one clove in each. Keep the pots somewhere protected over winter, and the plants can be transplanted outdoors in spring once conditions improve and the soil is workable.
See the range of garlic bulbs to plant at Amazon
See the range of garlic bulbs to plant at Walmart
See the range of garlic bulbs to plant at Burpee
See the range of garlic bulbs to plant at True Leaf Market
2. Microgreens
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As I mentioned, I worked as a professional kitchen gardener growing edibles for chefs. It included sowing and growing microgreens year-round. Even in December, I did weekly sowings of microgreens and harvested them multiple times a week during the month.
Microgreens are seedlings, harvested at only a few inches tall, but at this point, they are more nutrient-dense than their fully grown counterparts. There are many types of microgreens to grow, including pea shoots, radishes, amaranth, beets, and brassicas, in a greenhouse or on a windowsill.
Fill a seed tray with compost. Sow your seeds over the surface, sowing more thickly than usual, and press them down before covering with more compost or vermiculite. Here, I would advise placing the tray in a vessel of water to soak up moisture without disturbing the seeds.
This tray wants to be positioned on a bright windowsill or in a heated greenhouse. A heated mat and grow light will help encourage germination and healthy growth in the depths of winter. The microgreens can be cut once they are around two inches tall, once they have developed a second set of true leaves.
Discover the full range of microgreens supplies and seeds at True Leaf Market
3. Carrots
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A greenhouse can become premium real estate for the colder months, as it is an ideal spot to protect plants from frost. If you have space in a greenhouse remaining, you could start growing carrots, alongside overwintering plants indoors, for a spring harvest.
This can be done in beds in a heated greenhouse, if you have any, or you can grow carrots in containers in there. You will need a large container to grow carrots indoors if you want long roots, unless you opt for shorter or rounded carrot varieties, such as ‘Paris Market’ or ‘Short n Sweet’.
The best varieties of carrots for winter are smaller types or fast-maturing varieties, like ‘Early Nantes’ or ‘Amsterdam Forcing’. Carrots need warmth and ideally temperatures of 60-65°F. They can tolerate as low as 45°F, but growth will be much slower at lower temperatures.
It is the same when it comes to light; they want at least eight to ten hours, so they may need grow lights on for around 12 hours during winter if the natural levels are too low. The lower the light, the slower the growth.
Get Carrot ‘Short n Sweet’ seeds at Burpee
Get Carrot ‘Parisian’ seeds at True Leaf Market
Get Carrot ‘Amsterdam’ seeds at True Leaf Market
4. Cauliflower
They are often seen as a bit of an old-fashioned vegetable, but I have always loved growing cauliflower. They also have a reputation for not being one of the easiest vegetables to grow, and that brings with it a huge satisfaction when you harvest cauliflowers from your own garden.
It may seem early, but you can sow cauliflower seeds indoors during winter to plant out after the last frosts. The best varieties for this are early types, such as ‘Early White Hybrid’, and I have grown ‘All Year Round’ (which, as you may guess, can be grown year-round) cauliflowers in winter.
Sow seeds into individual pots or large modules, as cauliflowers quickly develop roots and can suffer from root disturbance when transplanted. As they will be spending winter indoors, you don’t want them to get too root-bound ahead of being planted out.
Cauliflowers should germinate well at temperatures of 60-68°F. They can handle down to 50°F, but will take a bit longer to germinate at colder temperatures.
Get Cauliflower ‘Early White Hybrid’ seeds at Burpee
Get Cauliflower ‘All Year Round’ seeds at Amazon
5. Mizuna
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Both mizuna and mibuna make fantastic cool-weather-loving crops to grow under cover in December in milder zones. If you are looking for an alternative winter green that is easy to grow, these are fantastic options, and you can harvest them as a cut-and-come-again vegetable for lots of pickings.
These Japanese greens differ in their leaf shape; mizuna has feathered, serrated leaves, and mibuna has narrower, spoon-shaped leaves. Both offer a mild spicy taste, which can add an extra flavor to winter salads when enjoyed raw or slightly cooked in stir-fries.
Mizuna doesn’t require lots of heat over winter to germinate and develop; it can thrive in a greenhouse, polytunnel, or cold frame in milder climates. You can also successfully grow mizuna on a windowsill to enjoy harvests of baby leaves within six weeks of sowing.
Other leafy greens you can plant in December include corn salad and winter lettuces. Both of these crops can be grown in an unheated greenhouse or on a windowsill to provide quick harvests.
Get Mizuna seeds at True Leaf Market
6. Onions
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It is a gardening tradition to sow onion seeds on Boxing Day. It is thought to be a key to growing bigger onions, and closely adhered to by gardeners looking to exhibit giant onions next year.
Not all growers are as fussed about planting onion seeds so early, but it can give your crops a head start at a quiet time of year, and they should be in fine fettle once the temperatures rise come spring. If you want to sow seeds on Boxing Day in the pursuit of larger bulbs, you can start growing onions in a greenhouse, cold frame, or on a windowsill.
Sow the seeds into trays or modules around a half-inch deep and cover with a thin layer of soil. Keep the soil moist and provide the seeds with temperatures of 50-60°F to germinate. The onion seedlings can be transplanted once they reach around 10 inches, after the last frost in spring.
Discover the full range of onion seeds at Amazon
Discover the full range of onion seeds at Walmart
Discover the full range of onion seeds at Burpee
Discover the full range of onion seeds at True Leaf Market
7. Fava beans
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While you usually plant fava beans in the fall or spring, you can get them in the ground in December for an earlier harvest next year. Just remember that the best way and place to plant them this month will depend on your local weather and soil type.
If you have mild winters and well-draining soil, you may have the opportunity to sow seeds outdoors. To make conditions more amenable to growing fava beans through winter, you can warm the soil and protect the beans with cloches, a portable cold frame, or a DIY cloche, such as using old glass frames or hoops and plastic.
However, gardeners in colder climates or those with heavy soil are advised to sow seeds indoors in pots in a greenhouse or on a windowsill to plant outdoors in the spring.
I have always found that ‘Aquadulce’ is a perfect type of fava bean for overwintering. It germinates at low temperatures, and over many years, I have found it a very reliable and consistent performer. It is an excellent choice for a top fava bean harvest every season.
Get ‘Aquadulce’ fava bean seeds at Amazon
Get ‘Aquadulce’ fava bean seeds at True Leaf Market
Shop seed sowing essentials:
These flexible silicone trays have 16 extra-large modules. The silicone cells help seedlings to ‘pop out’ when transplanting to avoid root disturbance.
Biodegradable Seed Starting Cells
This pack of 100% biodegradable peat pots contains five strips, each with 10 pots. Each of the 50 pots can be transplanted to prevent root stress.
This organic seed starting mix is made from natural coconut coir. It has a balanced pH blend and is suitable for sowing seeds of vegetables, flowers, and herbs.
Even though you may be planting vegetables in December, there should still be lots of crops to harvest this month in your yard. The likes of Brussels sprouts, kale, parsnips, leeks, and Jerusalem artichokes are among the best vegetables to harvest in December. The flavor of homegrown vegetables surpasses any you buy in stores, and many taste extra sweet this month as the frosts convert starches within them into sugars. What better than homegrown harvests on your festive plates this December?