For strawberries, covering is likely to be required in late October at the earliest, and covers used to advance the crop come off before 5% of flowers open.
Before ordering, write down the crop stage, where the roots sit and how exposed the site is to wind. Tell the adviser or supplier whether you are protecting raised strawberry bags, nursery pots or a field brassica crop, and whether the aim is winter survival, earlier growth, protection of young plants or insect exclusion. Fleece, insect net, lay-flat film and a tunnel do different jobs, so the job decides the material.
How frost cloth, a lightweight floating row cover, protects plants from frost
Frost cloth (also written frostcloth) is the same product as horticultural fleece: a lightweight cover laid over the crop.
A single layer of fleece protects strawberry plantings from several degrees Celsius of frost. Two layers of fleece protect slightly better than one layer of double-density fleece, because they trap more air for insulation. Short frosts of around -5°C are not harmful.
Flea beetle leaves pin-prick holes in young swede leaves, particularly in fine weather, and the white maggots feeding on the roots are cabbage root fly. Fleece or bionet crop covers are the best way to avoid both, and most of the commercial crop is now covered with insect nets. Cabbage root fly egg laying begins at the two-leaf stage, so the nets go on before then and stay on until the end of September.
When asking about brassicas, name the pest and the crop stage, and ask how the edges and access openings are handled. If a net is torn, record the location before repairing it, and tell the crop adviser if you find insects underneath; do not assume how they got in, because the material, the fitting and the crop history may all need checking. Mesh size decides what a net excludes when protecting brassicas from pests: a 1.3 mm net keeps out cabbage root fly; a 0.8 mm net also keeps out flea beetle and reduces aphid attack.
Ask the supplier which material, supports and fastenings suit your beds and your exposure, and treat a tunnel frame and its covering as one system: a different film or fastening can change what the frame was designed to carry. Before reusing an old roll, check its condition and write down tears and damaged edges; do not assume an unlabelled sheet performs like a new, specified one.
| Arrangement | What to decide |
|---|---|
| Fleece over plants | How it is anchored, whether it touches the foliage, how you will inspect and remove it |
| Insect net over a bed | Which pest it must stop, how the edges are sealed, how workers get in |
| Lay-flat film | Crop advancement, moisture under the film, access to flowers |
| Low tunnel | Hoop support, clearance over the crop, ventilation |
| Walk-in tunnel | Condition of the cladding, exposure, ventilation |
Covering strawberry plants for winter
Let the crop harden off before covering, because soft tissue is damaged most easily. Dormancy comes around the beginning of November at the earliest, and several normal frosts help harden the crowns before protection goes on.
Do not cover too soon, or soft growth follows. Do not aim for complete frost protection: cold is needed to maintain dormancy. Dormant plants have the best physiological defence against cold damage.
A max-min thermometer placed between the bags in the lowest, most frost-prone area shows what the crop actually experiences. Write down where each reading was taken, and note the time and place of the forecast you used: a regional minimum and the temperature at a raised root bag answer different questions. Agree who may open or change the covers during a cold spell, how that person is reached with an urgent reading, and leave the next shift a note of anything you changed.
Ask the supplier what an advertised temperature rating means: test conditions, duration, crop position and supporting structure. Do not choose on a single headline number.
Prepare before the cold arrives. Lay the fleece or polythene along the alleys ahead of winter and have a way to anchor the covers, for example bags of soil. Mark paths, turning areas and openings on a layout the relief crew can use, decide who fits the cover and who checks for displaced sections, and plan where removed material is stored and how it goes back on. Keep rolls labelled by crop and condition, and count the labour of repeated opening and closing when comparing options. Before committing the whole crop to a new system, ask for a practical demonstration of fitting and opening with the people who will use it out of hours. Report damaged supports or cladding to a competent installer instead of improvising a repair.
Cover removal and spring growth
British winters can turn mild, and covered crops begin to grow if not monitored frequently; crowns should be inspected regularly through the winter. As soon as the weather becomes milder, remove one layer but leave a single fleece for longer if needed. If an unexpected mild spell arrives, the fleece can be partially slashed rather than removed. Winter protection should never be allowed to accidentally advance crop development in spring. Any serious prolonged cold risks are likely over by mid-February.
Keep your spray records in one place. Free to start.
Plan access before you fit the cover: check how you will inspect crowns, foliage and roots (including the dampest spots under the fleece), how you will check substrate moisture and run irrigation while covered, and who will deal with a problem found underneath. If you find suspect material, photograph it with the cultivar, place and date rather than guessing a diagnosis from discolouration, and describe any unexpected growth to the specialist so you get a revised instruction. Fleeced crops stay wet for longer, and several weeks of soggy foliage develop Botrytis, which slowly rots the tops of the crowns; checking weekly and removing the covers to allow drying out is the remedy once it appears. Fleece encourages pest development in mild spells, so the canopy must be free of pests before covering. A fleeced, sheltered area encourages weed growth through winter, and rabbits that never reached a tabletop site can reach it once the plants are covered and low. In typical British winters the risk of desiccation is low unless there is much growth under the fleece.
For crops advanced under lay-flat polythene or fleece, remove the covers before 5% of the flowers open. This lets full pollination take place. List the other jobs that need access (harvest, inspection, irrigation repairs, any spray), schedule the opening and who reinstates the cover. If you plan a pesticide application, tell the adviser the actual structure and cover status, and check the Irish product guide and strawberry crop guide for that separate decision.
Keep two things apart: plants that are hardened and dormant through winter, and a crop deliberately advanced under fleece or film. Tell the adviser which one you have, and ask which plant observations should decide fitting, ventilation and removal.
Roots, containers and wind
Map the crop before winter: its height above the ground, drainage, and exposure to the prevailing wind, marking raised gutters, exposed ends and outside rows. These, together with container sides and root bags, need protection first. A cross-section sketch of the bed or tabletop (crop, support, substrate, cover, ground, gaps and openings) kept beside the temperature record helps you read the measurements later. Reduce the surface area of containers exposed to the cold to improve root insulation. Placing troughs side by side reduces cold edges and lowers the risk of cold damage. Reducing the surface of bags and troughs exposed to wind reduces wind injury, and a perimeter of straw bales or bunched fleece or polythene reduces the chilling effect at the edges. A polythene sidewall down the windward edge helps too, but cold air must still be able to drain away.
Overwintering height is a significant protection factor. Systems almost at ground level, such as draining mats or raised wires, benefit from daytime heat reserves, suffer minimal wind chilling and do not need to be moved.
Lay a permeable membrane, such as fleece or woven polypropylene, between the ground and the crop. Avoid dirty, weed-seed-infested fleece. Holed polythene is harder to irrigate through overhead if drought arises. Strawberries are a hardy perennial and capable of surviving most British winters unaided.
Tabletop crops are exposed to wind and freeze faster than crops at ground level. A double layer of fleece matters most there, and wrapping loosely bunched fleece over the top and sides of the bags under an outer layer of permeable polythene encloses the most insulating air. Such a cover is hard to remove and reinstate compared with a ground-level crop.
If you plan to move containers, agree handling and space before the weather event, note which groups move and which stay, and keep plant labels linked to the crop history. Check the bed and the drainage routes around it for places where water collects, and have blocked channels cleared. Container stock should enter winter acclimatised, in good condition, with adequate nutrient reserves and good drainage. Keep ventilation under structures and thermal covers.
Container stock and nursery plants in winter
Excess water is the single biggest cause of winter losses in hardy nursery stock, so reduce irrigation as winter approaches and keep container beds well drained. Avoid high-nitrogen feeds for autumn potted material because they encourage soft growth. Do not bring outdoor container stock inside too early: soft autumn growth is more liable to winter injury.
Low tunnels, walk-in tunnels and winter protection for a greenhouse
Low tunnels suit low-growing crops and shelter in the early stages of a crop's development: a roll of 150-gauge polythene is supported by wire hoops and secured by twine. Walk-in tunnels are a low-cost alternative to glasshouses: 600-gauge polythene drawn tight over galvanised metal tubing. They raise plants and grow tender or out-of-season vegetables such as tomatoes, cucumbers, melons, aubergines and sweet peppers. Dutch lights, polythene tunnels and polythene mulch all help raise out-of-season and frost-tender vegetables. For tomato plants and frost, the point is the same: plant out only when all danger of frost is gone.
Black polythene laid on the ground and secured at the edges helps many tender crops grow better than planting into open ground. Raise the plants indoors or in a heated frame or glasshouse, then plant through holes in the mulch. Tomatoes, gherkins, marrows and sweet corn benefit most. Raising the plants indoors protects seedlings from frost until they are planted out through the holes in the mulch.
Double-skinned tunnels protect typically down to 5°C. Glasshouses used for overwintering are set between -1°C and +5°C, with additional heat of up to 5°C during very cold spells. Ventilate polythene tunnels, glasshouses and thermal covers as conditions allow, to control Botrytis and maintain winter hardiness.
Next step
Match the cover to the crop: for strawberries read the strawberry protection guide, and for birds use the fruit bird protection guide.