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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April...hmmm, let me see – oh yes, showers. Well, that’s not going to bother me in the polytunnel! It’s a wonderful gardening space at any time of year, but particularly when it’s chucking it down outside. It’s almost always warmer, and the air is calm. It might be a bit noisy, but that’s only because of what’s happening outside.
April is the month when the polytunnel gardener has to start taking care of two vitally important things on a daily basis: ventilation and watering. The sun in April is as strong as the sun in August, even though it might not feel as warm. In the sheltered space of the tunnel the interior can heat up extremely quickly. Unless you’re careful, the combination of heat and a lack of water (because watering is entirely up to you and not the rain) will quickly lead to crop loss. Make sure the tunnel doors are open early in the day to prevent the interior getting too hot, and water as often as your plants need it. While this might sound vague, it really depends on your soil type. Sandy, well-drained soil could easily need watering daily; heavier, clay-based soil might only need it twice a week.
While you might not have noticed many slugs beforehand, in April they start to appear – and breed. Dealing with them now means a much reduced slug population later in the year. They tend to be out and about after dark, so get a torch and a collection pot and head off to the garden for a stroll every other evening. You’ll be amazed how many there are!
If you planted for the ‘hungry gap’ and timed things right with staggered sowing last year, you should still be enjoying all kinds of vegetables in the polytunnel. Be sure to make notes of sowing times, conditions, planting-out times and varieties. If it all works, you’ll want those notes again next year...and if it doesn’t, you’ll want to check them in order to avoid repeating your mistakes.
Hopefully you already have staging prepared for seedlings. Keep sowing! Lots of summer crops can be started in pots in the polytunnel and planted outside later.
If you didn’t make a crop rotation plan yet, you probably should make one now. April is a transition time between winter, the hungry gap and summer crops. While it might be tempting to fill every space that appears with a lettuce, don’t get carried away. A crop rotation tells you exactly what grew where last year and over the winter, and shows you exactly where to put your summer crops to avoid pests and soil depletion. Crop rotations are especially important to organic gardeners who don’t rely on chemical fertilisers and insecticides to create the appearance of a healthy growing environment. If you want a truly healthy garden, make a rotation plan and stick to it. You need a minimum of a three-year rotation in a polytunnel, but a four-year plan will be even better. For a ‘starter’ rotation plan, see chapter 8 of ‘How To Grow Food In A Polytunnel’.
Avoid transplanting shock whenever possible. Lots of summer crops, including peas, beans, cucumbers and squash, hate being transplanted and their roots are easily damaged. To get around this problem, sow them in biodegradeable pots – then you can just plant the whole thing with no transplant shock at all. Seeing the roots begin to grow through the sides of the pot is usually taken as a sign that it’s ready to plant, but in fact it’s better to wait just a little longer. ‘Air pruning’, the process of allowing these exposed roots to dry out and die, promotes lateral (rather than longitudinal) root growth within the pot. It’s a process which is actively encouraged in the horticultural industry as it generally ensures a much healthier plant. Just don’t let it go too far!
If you decide to invest in a soil thermometer, don’t get one which contains mercury, as if it breaks it will add a very, very serious poison to the earth.
Keep a bag of compost to hand so that as gaps appear you can add more nutrients – as well as more plants.
Sprouting broccoli, cabbage, carrot, cauliflower, chard, coriander, courgette, cucumber, dwarf French bean and French beans, fennel, kohlrabi, lettuce, melon and watermelon, radish, rocket, spinach, spring onion, strawberries.
Aubergine and tomatoes are now off the list as ideally they should have been sown before April. If you forgot, give some a try – you never know, you might still get a crop.
Everything on both the ‘sowing’ and ‘harvesting’ lists, plus peas, broad beans and potatoes.
Broad bean, sprouting broccoli, cabbage, carrot, cauliflower, celeriac, celery, chard, coriander, kohlrabi, lettuce, peas, radish, rocket, spinach, spring onion, strawberries, turnip.