Brrrr…it’s cold outside, but in the relatively cosy confines of my cold frames, my winter salads are doing well.

It’s a genuine pleasure to lift the lid on a frosty morning, and find vibrant, healthy salads ready for the picking. Cold frame growing is also a very simple and easy form of gardening, and a useful way to extend the season. Here are the main plus points:

Cold frames offer that little extra bit of protection from the weather, and are a couple of degrees warmer than the outside temperature. As long as the lid is on, they protect from snow, frost and damaging storms with their torrential rains and high winds. This means crops are less stressed and more able to keep actively growing.

Cold frames protect from debris and leaves. This is especially great if, like me, you garden beneath trees. We have mature maples at our allotment, and the big leaves can smother delicate salads and encourage rot, and also tend to be a favourite hiding place for slugs and snails. The lid also stops hundreds of maple seeds from getting in and germinating in the spring. Living without this annoyance has definitely improved my gardening experience!

Cold frames keep crops cleaner and mud-free. All I have to do is give my salad leaves a quick rinse, whereas those grown outside need more labour-intensive washing and drying.

Pests tend to be less of a problem. Although one or two small snails did creep into my cold frames and have a crafty munch, the cold frame is a more controlled environment, so it’s easier to pick out problematic creatures such as slugs and snails.

Weeding is easier. Whereas the world outside my cold frames is a Wild West of weeds that I do battle with only every now and then, the cold frame is much less daunting as a weeding task. The main thing is to ensure that any difficult perennial weeds are completely removed before you place the cold frame – I learnt from bitter experience that if you don’t do this thoroughly, they will keep coming back.

So what can you grow in your cold frame?

Well, there are height restrictions, so it’s best for low-growing crops! I find growing a mix of salad crops like oriental greens (mizuna and a selection of mustards) and rocket is a great combination. These cut-and-come-again crops will give you many harvests over the winter, if you cut a few leaves at each harvest but leave the root system intact. Lambs lettuce is also an easy low-growing crop for a cold frame; it enjoys the cooler and damper environment than it would get in a greenhouse. I’ve also grown radishes and spinach successfully in cold frames.

How to get started?

The best time to sow your salad crops for winter harvests is in August and September, although I’ve also gotten away with sowing as late as early to mid October in years with warm autumns. Prepare the ground in your cold frame by weeding thoroughly and add in some nutrition. Homemade compost and well-rotted manure or organic fertilisers such as poultry manure pellets are all good. I’ve also added coir in to improve texture and drainage on heavier soils. Keep well watered when plants are seedlings, and if you’re sowing in hot late summer or early autumn weather, keep the lid off at this stage.

To keep your crops growing healthily, make sure they are getting enough water and have good ventilation. If the lid is on, place it so that there’s a ventilation gap to allow air flow. Most ready-to-buy cold frames come with adjustable lids.

If you like DIY, you can also have a go at making your own cold frame. We (or to be more accurate my handy other half!) made a box with timber planks for the frame. We then used leftover polycarbonate from our greenhouse project for the lids. Polycarbonate is a great choice as it has good insulation whilst also letting plenty of light in, and is easy to handle and cut to size.

When spring comes along, you can put your cold frame to other uses. It’s a great way to extend the growing season by starting off crops earlier than you would in the open ground. The extra warmth and protection aids germination and protects delicate seedlings. For example, you can get your carrots in a few weeks earlier using this method. You can even start off taller crops like peas, mange-tout, and beans with the help of the cold frame, removing the lid once they’re established.

Cold frames are also useful in spring for hardening off plants that have been started off inside and need to get acclimatised to outdoor temperatures gradually. They also offer a bit of winter protection for winter pot plants and bulbs – for example if you want to stop bulbs planted in pots from getting too wet and rotting.

Hope that’s given you a few ideas on how to get the best from cold frames. After using them for two or three years, I now can’t imagine gardening without them, they are just so very useful!