Tunnel vision

Did your polytunnel get the better of you this summer? Never fear – there’s plenty of time to get it ship-shape and primed for year-round production

Sat, Aug 23, 2014, 01:00

If you belong to that growing band of Irish gardeners who are proud owners of a polytunnel, then this is the month when the latter should, by rights, be filled to bursting point with delicious produce. With aromatic tomato plants, for example, their leafy stems laden down with heavy trusses of scarlet, golden and indigo-coloured fruit. Or bamboo wigwams draped with climbing French beans so tender that you’d happily eat them raw.

Also, bitter-sweet peppers, fiery chillies, mouth-wateringly tasty cucumbers and plump, golden cobs of sweetcorn, as well as juicy strawberries that melt in the mouth, sweet melons dripping with flavour, sun-kissed peaches and succulent grapes. Ideally, you will also already have planned for the larder-pinched months ahead with a July sowing of various vegetables, all of which you’ll later use to fill up the spaces left behind by high-summer’s crops.

But then again, maybe not. After all, we’re only human, and maintaining that delicate balancing act of regular sowing, watering, ventilating, feeding, and harvesting is a feat of organisation requiring an amount of forward planning.

So perhaps this was, instead, the summer that your polytunnel got the better of you. The summer when plants went un-watered for a little longer than they ought to have, or garden pests – slugs, caterpillars, cut worms – stealthily chomped their way through young crops before you had the opportunity to stop them. If so, don’t despair, because all is not lost. In fact, there’s still enough time to get your polytunnel ship-shape and primed for all-year-round production.

My advice is to begin with a really good clear-out. Start by digging up and composting any healthy [annual] plants that have finished cropping or have bolted, before weeding the ground, carefully and systematically. With persistent perennial weeds, it’s vital to dig out the root system in its entirety. Whatever the weed, it’s also important to prevent it from seeding around the polytunnel, so carefully bag any ripe seedheads before they have a chance to do so.

Closely examine remaining crops for any early signs of disease or pest infestation. At this time of year, common fungal diseases such as grey mould (botrytis) and powdery mildew can become a serious problem in a polytunnel, stunting growth or, in the case of grey mould, sometimes killing the plant entirely. So search for early signs (in the case of grey mould, a powdery grey coating, in the case of powdery mildew, white spotting on the leaves) and gently remove, bag and burn any infected plant material promptly. While you’re at it, remove any other damaged or dead foliage that you might spot.

In the case of grey mould, a combination of high humidity and inadequate ventilation is the primary cause, so try to ensure good air circulation by opening polytunnel doors during the day. In the case of powdery mildew, the main cause is inadequate watering, so give the soil a good once-off soaking at ground level (in the morning), carefully avoiding wetting any plant foliage. Tomato plants in particular can get out of hand at this time of year, increasing disease problems. So nip out any errant sideshoots on cordon-types as well as the growing tips, remove leaves below the first truss and tie up loose stems.

As for those pests? Use organically-approved pellets/ beer traps/ hand collection to get rid of slugs and snails. Handpick caterpillars and squash any eggs that you find. If they’re a problem, hang up sticky traps to catch whitefly and sluice greenfly off plants with a spray of water.

Finally, remember that more than anywhere else in the garden, the soil in a polytunnel needs regular feeding, as do the plants at this time of year. With remaining summer crops (tomatoes, cucumbers, melons, peppers, strawberries) give them a regular liquid feed (every 10-14 days), continuing until they stop producing. Use either a good quality proprietary brand of liquid tomato-feed (ideally one with added seaweed extract) or make your own, using comfrey and nettles. Once one crop has finished and has been cleared away, I always aim to replenish nutrients in the soil with a top dressing of homemade compost before replanting.

But replant with what, I hear you say . . . Well, happily there’s still enough time to grow plenty of different polytunnel crops from seed, either into modules/pots for transplanting later, or alternatively by sowing directly into the ground.

Swiss chard for example, whose brightly colourful leaves taste as good stir-fried in soy sauce, garlic and olive oil as they do in an apple pie. And cabbage, especially the varieties “Greyhound” and “Hispi”. Also iron-rich kales such as “Cavolo Nero” and “Ragged Jack”, early-Nantes-type carrots, leaf chicories, spring onions, perpetual spinach, and some varieties of turnip including “Snowball” and “Noir d’Hiver”.

And of course, oriental greens and salad leaves such as lamb’s lettuce, land cress, rocket, varieties of winter lettuce, pak choi, mibuna, mizuna, kailan, salsola and mustards as well as herbs such as coriander, chervil, parsley and sorrel. Even, if you hurry, Florence fennel.

So forget the fact that your polytunnel may have got the better of you this summer and instead, grab your chance to fill the hungry gap of next spring.

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