Welcome the First Tunnels Growing Guide. We know how to make great polytunnels, how to construct polytunnels and tailor a polytunnel to an individuals preference but we’re not gardening experts. Thankfully we work with several of the countries leading polytunnel gardeners, people who have been using our polytunnels for years. Each month this year we will produce a growing guide working closely with Mark Gatter, author of 'How to grow food in your polytunnel'. Mark has years of experience and has kindly offered to share some of the hints and tips he’s picked up over the years
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March often feels as if it’s still winter, especially with it’s famous ‘March winds’ which can quickly make you wish you were back inside where it’s warm. But in a polytunnel, the wind isn’t a problem and you can focus instead on what’s happening to all your overwintering plants – which are suddenly growing, and many of which are either actively bolting or thinking about it.
Broad beans and peas planted in January should begin to flower this month. However, if you planted them in late autumn they will be developing small pods. These will become a valuable source of food in the ‘hungry gap’, when there’s nothing much left from winter and the spring crops aren’t yet ready, which begins around the end of the month.
Overwintering plants such as celeriac, lettuce and pak choi will be very keen to bolt this month, but you can delay things by trimming off all but a few leaves. This will slow them down enough to allow you to continue to enjoy them well into April.
Celery will have recovered from the winter lull and should now be producing some beautiful edible stems. It won’t last, so make the most of it!
While frost will have invariably killed off all my outside chard, the polytunnel plants will have survived but are now determined to bolt. However, one of the great things about chard is that the flavour of the leaves doesn’t change, and as bolting is a long and quite spectacular process (flowering chard plants well over 2m tall...) they will tide you over until the younger plants are ready to pick from in June. A few plants in the polytunnel guarantees a year-round crop of this, surely one of the most valuable of all the ‘green leaf’ plants – and one that you hardly ever see in the shops.
If you started off any tomato plants under lights in January they should begin flowering about now. As it’s roughly 60 days from seed to flower and another 60 days from flower to fruit, early tomato flowers means a crop that you can be enjoying long before any blight appears.
If you planted elephant garlic in October it should really be getting going now, and may easily be well over a foot tall.
Sometime in March your polytunnel will take over from windowsills and cold frames as the best place for new seedlings, so you need to provide somewhere where they will a) get plenty of light and b) won’t be constantly in the way. Rather than taking up valuable floor space, why not hang some staging from the crop bars? Ideally you want something that light can penetrate so only a little shade is cast on the beds beneath. A simple wood frame made from some scraps of 25x50mm and covered with a sheet of rectangular wire mesh (or similar) is ideal. Then, once your plants are big enough to go into a bed, you can take the staging down until it’s needed again. Mine usually goes up in March, comes down in May, and goes back up again in late August for the autumn/winter crops.
As you take out the overwintering plants, fork in some new compost so the beds can sustain the season ahead – unless, of course, you are growing crops that prefer soil that is not too rich, such as carrots. Always keep note of what grew where so you can maintain a good crop rotation. This avoids nutrient deficiencies and also breaks the cycle of pests and diseases which can otherwise turn into a major problem.
March offers us a wide variety of weather. On colder days it’s easy to forget that in the warmer climate of the polytunnel, plants are coming out of dormancy and therefore need more water than at any time over the past several months. Don’t forget ventilation, either, or you could have a lot of sick plants on your hands. Taking care of both these will help ensure everything gets off to a great start, and stays that way.
Aubergine, cabbage, carrot, cauliflower, celeriac, chard, coriander, fennel, garlic/elephant garlic, kohlrabi, lettuce, spring onion, peppers, radish, rocket, spinach, strawberry plants, tomato.
March is actually a bit late for peppers. They do best when started really early, so if I planted them in February I don’t usually sow more in March. However, if you missed February, do it now! You should still get a decent crop.
Everything on both the ‘sowing’ and ‘harvesting’ lists, plus peas, broad beans and potatoes.
Beetroot, sprouting broccoli, cabbage, carrot, cauliflower, celeriac, celery, chard, coriander, kohlrabi, lettuce and other salad greens, spring onion, pak choi, radish, rocket, spinach, turnip.