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

This month See how sliding doors make ventilation a breeze

For me, once May begins summer has arrived – whatever the calendar says. For example, in 2010 ‘midsummer’s day’ was June 24th (as usual). However, and confusingly enough, midnight on June 21st was the beginning of the first official day of summer. Now, just how the first day of summer can be only three days from its middle is beyond me – and incidentally would mean summer was slightly less than a week long, which, even if true is very depressing indeed. So I just go by When It’s Warm...which means May – the sun is (probably) shining, and the polytunnel is absolutely exploding with growth.

May is one the most exciting months for the polytunnel gardener. All the plants suddenly seem to be quite capable of taking care of themselves, or even taking over completely if you let them. So, one important ‘thing to do’ in May is – don’t let them!

Any remaining overwintering plants, apart from broad beans and peas, are probably bolting like crazy. Most of them should have been removed by now as they either become woody, lose their flavour or both. Chard, on the other hand, stays tender right up to the point of collecting seeds, by which time it can be well over 2 metres tall and casting a very big shadow indeed. So, it’s unlikely to be something you allow to go to seed every year – and of course you won’t need to. A single chard plant will produce enough seeds for years, as well as plenty for your friends.

If you haven’t tried saving seeds before now, do give it a try this year. It’s easy, fun and incredibly productive. And, you are very likely to end up with better plants as a result. Don’t bother with hybrids (‘F1’ varieties) as the seed won’t breed ‘true’. Instead, look for ‘open pollinated’ (i.e. pollinated by wind or insects) varieties. So long as you don’t allow them to cross with other species (some will if you let them, such as carrots with Queen Anne’s Lace), these will breed ‘true’ – which is to say, they adapt. Instead of perfect clones, you get slight variations within a particular type. If you only save seeds from the best plants, i.e. those which were the last to bolt, and/or the healthiest and most productive – you might end up with something really worthwhile, and possibly even a whole new variety.

Lettuce, peas, tomatoes, climbing French beans – all these produce self-pollinating flowers and there’s very little need to worry about them crossing. Others are more difficult and may require isolation or protection. For lots more information on just how to save seeds from specific varieties as well as a list of useful seed suppliers, see ‘How To Grow Food In Your Polytunnel’.

Top Tips

Many insects take to the air in May. Some are good for the garden (hover flies, bees, ladybirds) and some are bad (butterflies, aphids, carrot fly, flea beetles). All of them will find your polytunnel, and some might decide it’s nice enough to stay. By hanging weighted mesh curtains across the polytunnel door openings, air can still circulate but you can keep most of the insects out. However, be warned: If you completely exclude insects, you will either have to go without particular crops (strawberries, for example) or pollinate the flowers by hand. This can usually be accomplished with a fine paintbrush, but it’s very time-consuming. Instead, you might try a compromise: a reasonably coarse mesh will allow everything but butterflies through, so at least you can get a decent cauliflower crop!

Keep up the evening ‘slug patrol’ as this is their peak breeding time. Water in the mornings, so that leaf surfaces have time to dry before the evening. That makes it harder for slugs to get around, and there is less likelihood of mould developing. For the same reasons, don’t let plants crowd each other. The health of your polytunnel depends on good air circulation as well as water and nutrients.

What to grow... View Top of the Crops

Sowing:
Sprouting broccoli, cabbage, carrot, cauliflower, coriander, courgette, cucumber, daikon, fennel, kohlrabi, lettuce, melon and watermelon, radish, rocket, spinach, spring onion, sweetcorn.

Don’t forget to sow some sweetcorn! Polytunnel plants will be ready three to four weeks ahead of those planted outside, extending what is surely one of the best crops of the year.

Harvesting:
Broad bean, sprouting broccoli, cabbage, carrot, cauliflower, chard, coriander, kohlrabi, lettuce, onion, pak choi, peas, radish, rocket, spinach, spring onion, strawberries, turnip.

(I’m leaving out ‘growing’ for this month as it’s all the plants on the ‘sowing’ and ‘harvesting’ lists, and should be for the next few months.)

© Mark Gatter 2011

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Download the First Tunnels May Growing Guide (PDF 890KB)

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