Growing guide: What to sow and plant in December

Premier team

Whether you’re a seasoned professional or a hobby gardener, you may have found that some vegetables can be difficult to grow in the winter. With shorter days meaning daylight levels are lower and with the biting cold setting in, it’s no surprise that yields can sometimes be disappointing.

However, that doesn’t mean that there aren’t some hardy seeds and vegetables to plant in December. Provided the conditions are right, you can still have a successful harvest over the winter months – if you have the right equipment, that is.

In fact, winter sowing can mean you have a better succession of harvests later, compared to simply sitting back and waiting until spring.

No matter if it’s your first time growing vegetables or you’ve done it all before, you can (and should!) make the most of the winter months and get some crops underway.

Having helped professionals and gardening amateurs for over 30 years, we’re on hand to help you yield a successful harvest with our winter growing guide.

To find out what the right seeds to plant in December are, read on.

What to plant in a polytunnel in December

With the festive season upon us, it’s not uncommon for the little work to be done inside the polytunnel this month. Many polytunnel gardeners will be clearing the last of the year’s crops and preparing the beds for the next busy growing season, while other will be enjoying some winter gardening.

If you're wondering what to plant in a polytunnel in December, you’re not alone. Many gardeners can struggle to know which plants will thrive under the protection of a high-quality polytunnel.

However, we can tell you that a polytunnel will help winter vegetables thrive by offering protection from the elements – in particular, frost.

To help make life easy, we’ve put together a list of what to veg to plant in December in the UK.

Seeds to plant in December

Broad beans

These hardy crops can be sown in December and will yield as soon as April. After you’ve sown these seeds, they should germinate in a fortnight or so. Broad beans are a great vegetable to plant in December in the UK as they’ll thrive under the extra protection of our durable polytunnels.

As a bonus - they help improve the soil too!


If you’re partial to a lunchtime salad, the good news is that lettuce is one of the few crops that can be grown all year! Certain varieties of lettuce such as ‘Winter Gem’ are renowned for their ability to grow in harsher conditions and tend to thrive in a polytunnel.

Simply sow your lettuce seeds in the ground inside your polytunnel and away you go. As lettuce takes up little space, it’s a great winter vegetable to grow, even if space is limited.

Mangetout Peas

Nothing tastes better and sweeter than freshly picked, home-grown peas. Possibly one of the most popular crops that doesn’t make it out of the polytunnel before being eaten as a healthy snack, if you do manage to get your harvest to the kitchen, mangetout peas can be used in many recipes. They are also perfect for freezing.

December is the time to plant out seedlings which have reached 8cm tall or, if you haven’t already, sow seeds ready for an early spring crop.


Although often used in exotic recipes, coriander is exceptionally resilient. A relative of parsley, this hardy herb does well in light or shade, pots or soil.

While normally sown from spring to autumn, with a polytunnel or cloche you can sow batches in the autumn and winter and extend your yield, according to the Royal Horticultural Society.

Garlic seeds

Garlic is a low maintenance plant and is an ideal choice for over-wintering as it thrives in cold temperatures.

If you can get hold of them, garlic seeds can be planted in the winter in well-drained soil. Not needing much light to grow, old gardening wisdom says garlic should be planted on the shortest day of the year.


Frequently found in fine dining establishments, microgreens are young vegetables that fall somewhere between a sprout and a baby green. Intense in flavour, microgreens add colour and flavour to dishes such as stir-fry, salads and soups.

Microgreens are great for polytunnel growing in December and are typically ready to be picked a few days later, so you can have tasty meals all year round.


No list of vegetables to plant in December would be complete without a nod to kale. Kale is suitable for overwintering, but it’s best to start the seedlings indoors in a tray or propagator before transferring them to a polytunnel. For the best results, be sure to plant each seedling 15cm apart.

Thought of something not on the list? Check out our yearly polytunnel planner for more ideas on when to sow your winter crops.

What to harvest in December

If you’ve successfully grown winter vegetables in your polytunnel, you may be wondering what’s suitable to harvest.

The below plants are usually suitable to be harvested in December – providing you’ve done your planting right!

  • Kale
  • Turnip
  • Winter cabbage
  • Beetroot
  • Spring onions
  • Carrot
  • Lettuce
  • Pak choi
  • Kohl rabi
  • Radish
  • Spinach
  • Chard
  • Fennel
  • Potatoes

How to maintain your polytunnel

Although polytunnels are generally an easy, low-maintenance way to grow vegetables in winter, they do require a little TLC. By following a few simple steps, you can keep your polytunnels working at their peak for months to come.

  1. Water carefully

In the UK, we have a wet winter as it is. Therefore, it’s important to not overdo the watering. Normal advice for December is to keep watering to a minimum as damp soil and foliage encourages fungal diseases. Soil may look dry, but it’s a good idea to check just below the surface with your finger or a trowel. Plants in pots, however, are likely to need more water.

Pots from outside should be brought inside the polytunnel to protect from waterlogging, cold winds, and very low temperatures.  

  1. Insulation

December Growing Guide for PolytunnelsIf possible, insulate the polytunnel by covering ventilation and doors with bubble wrap.

If you have opened the doors during the day, remember to close and secure the polytunnel as night falls – plummeting temperatures could wreak havoc on your vegetables.

Use a Polythene Cloche inside your polytunnel to act a ‘double glazing’ during the winter months, keeping the frost off your crops and keeping heating costs down.

  1. Clean up debris

If you fail to clean up debris and waste from your polytunnel, it will become a breeding ground for mould, pests and all matter of other unmentionables. Make sure to clean your polytunnel and wash pots to avoid diseases being carried through to spring.

  1. Protect from snow

The weight of snow left to lie on the polytunnel roof can put the frame under strain and cause the cover to stretch, therefore it’s important that you don’t let too much snow sit on the roof of your tunnel.

Make sure you remove excess snow as soon as you can by tapping on the side of the polytunnel cover and on the roof inside, if you can reach. Knock snow from the harder to reach areas by using a soft brush.

We can help with polytunnel growing in winter

For an environment that lends itself well to growing vegetables in winter, browse our high-quality range of polytunnels.

If you have any questions or just want a second opinion, contact us on 01282 811250 or email One of our customer service advisors will be happy to help get you up and running.