Using Cloches And Fleece To Extend The Growing Season

Why a Little Cover Goes a Long Way

Anyone who has gardened in Britain for more than a season or two knows the pattern: a glorious warm spell in late March coaxes everything into growth, then a sharp frost arrives in mid-April and blackens the lot. The same happens at the other end of the year, when an early October cold snap catches your tomatoes before they have ripened. Cloches and fleece are the simplest, cheapest defence against that unpredictability — and used well, they can buy you three or four weeks in spring and a similar stretch in autumn.

Neither is a magic wand. They work by trapping a layer of warmer air around the plant, raising the temperature by a couple of degrees and, just as importantly, shielding leaves from cold wind and driving rain. That small difference is often all that separates a thriving seedling from a sulking one.

Choosing Between Cloches And Fleece

The two do similar jobs but suit different situations.

• Cloches are rigid covers — glass, plastic, or polycarbonate — usually shaped as a bell, tent, or long tunnel. They give strong protection and warm the soil beneath them, which matters early in the year when cold ground stalls germination. They are best for individual plants or a single row, and they last for years if you store them carefully.
• Horticultural fleece is a lightweight spun fabric you drape directly over plants or lay over hoops. It lets light and rain through, weighs very little, and can be doubled up for extra insulation during a hard frost. It suits whole beds, and it is far more forgiving if you forget to open it on a sunny morning.

Most productive plots end up using both: cloches for the earliest sowings and treasured individual plants, fleece for larger areas and for quick, temporary cover when a cold night is forecast.

Getting The Most From Cloches

Timing is everything. Put cloches out a fortnight before you intend to sow, so the soil underneath has a chance to warm through. A soil thermometer pushed in to 10cm will tell you more than the calendar ever can — once it holds steady at around 7°C, hardy salads and early carrots will germinate happily.

Ventilation is the mistake nearly everyone makes in their first year. On a bright day, a closed cloche can reach 30°C or more inside, and seedlings will cook or stretch into pale, leggy weakness. Lift the cover, prop it open, or slide tunnel cloches along the row for a few hours around midday. On still, sunny days from April onwards, that often means opening them every morning and closing them again in late afternoon.

Watering needs care too. Cloches shed rain, so you must water by hand, and always in the morning so foliage dries before the cooler night air arrives. Watch for slugs and snails, which adore the damp, sheltered conditions underneath, and check the undersides of leaves for aphids, which build up quickly in still air.

Using Fleece Well

Fleece earns its keep in several ways. Laid over newly sown rows, it speeds germination and keeps cats, pigeons, and carrot fly at bay. Draped over tender crops in September, it can carry runner beans, courgettes, and late salads through the first light frosts. Even a single layer raises the temperature by two or three degrees; a double layer, or fleece over a cloche, can gain you a few more.

A few practical points make a real difference:

• Lay fleece over hoops or canes rather than directly on leaves, so growth is not bruised and air can still move.
• Secure the edges with soil, stones, or pegs — wind will find any loose corner and shred the sheet.
• Remove it on mild, sunny days. Fleece cuts light by around 10–15%, and plants kept under it for weeks will be softer and more frost-tender, not less.
• Lift it for pollination once flowers appear, or bees and other insects will not find their way in.

Hardening Off And The Wildlife Question

Plants raised under cover are cosseted, and they need a week of gradual exposure before facing the open garden. Start by opening the cloche or lifting the fleece for a few hours each day, extending the time until the plants are out overnight. Rushing this stage is the commonest reason for a crop that collapses the moment protection is removed.

There is a wildlife angle worth thinking about. Cloches and fleece are useful barriers against pests, but they also exclude pollinators and beneficial insects. Hedgehogs, frogs, and ground beetles will happily shelter under a low tunnel, so check before you move one, and leave a gap at the ends of long cloches so creatures can pass through rather than becoming trapped. Native bees emerging on a warm February day will be grateful for a few early flowers left uncovered.

A Simple Seasonal Routine

From late winter into spring, cloche your beds a fortnight ahead of sowing, vent daily, and water by hand. As the weather settles in May, wash covers down and store them somewhere dry and out of the sun, where plastic will not go brittle. In late summer, bring fleece back out for the first cold nights, protecting late salads, herbs, and any tomatoes still ripening on the vine. Through winter, cloches over winter salads or hardy herbs will keep a modest harvest coming when little else is on offer.

None of this is complicated, and none of it is expensive. A few pounds spent on fleece and a couple of sturdy cloches will repay you many times over, not in dramatic transformations but in the quiet, steady gains that make British gardening such a pleasure — a fortnight earlier in spring, a fortnight later in autumn, and far fewer disappointments in between.