You can easily say that the polytunnel turns our four seasons into three, a warmish bit, a very warm bit and a cool bit. The winter is six weeks late and the spring a couple on months early. Not only is it useful to get your frost sensitive summer plants a good start, you can fill in the hungry gap with plentiful crops.What to grow in winter can always be a quandry.
Not so spring clean
The problem with using the polytunnel intensively is that pests and diseases can easily build up, particularly as the soil is hardly ever heavily frosted. Choose a day after the major crops have been removed and give it a good wash with garden disinfectant (Don’t you just love the small?) Clean the outside as well as the inside, the paths and the soil that is not planted up. A good wash will allow more light through for those precious winter crops.
What to grow
Potatoes in large pots do well. Plant in September, watering lightly. By Christmas you could well have some new potatoes to harvest. In hot South America they plant potatoes on December 1st some 14 weeks earlier than here at home. The polytunnel makes it possible for you to have new potatoes by Easter.
Broad beans and peas can be sown in late November and will crop in April. Carrots sown in October in a mixture of sand and compost will do very well.
You can sow lettuce, endive, beets, baby spinach and various salad leaves such as rocket. Sow from September onwards right through to November and beyond. Use these as crop and come again through the winter.
Courgettes grown in ring culture pots, if you have the space, will crop in March / April if sown in December in a lightly heated space in the polytunnel.
You can plant onions in December, but the normal outside regime is probably best, and there is not muck benefit in planting garlic because to get the very best they do need some frosting.
Watch out for disease, which will not really be a problem is the temperatures are on the cool side. You might choose to spray once a month with Bordeaux Solution to keep botrytis and other fungal problems at bay.
Remember, even in the winter daytime temperatures can reach double figures outside, so on warm days open the doors for a bit of ventilation. However remember that heat is expensive and plants are precious, so keep it shut on cold days. A single icy blast can stop plants from growing for a couple of days.
Plants have immune systems just like people, although they work much differently. A chilling can shut this down and the plants become vulnerable, so aim to keep the temperature as warm as possible.