The premium enjoyed by a successful early crop is one of the benefits to be had from using the right sort of fabric to give thermal protection against frosts and to warm soil and air temperatures for early production. Spun-bonded polythene fleeces, fine knitted netting and some plastics film mulches can also offer protection against other weathers, including rain, hail and wind, along with eliminating damage from insects, birds and rabbits - helping improve both quality and yield.
Salad, vegetable and fruit growers take advantage of the micro-climates afforded by fabrics but nursery stock growers, professional gardeners and landscapers can also use fleeces to shelter less-than hardy subjects.
Manufactured materials are often preferred over the traditional wrapping of bracken which may retain too much moisture and cause plants to rot.
The best fabric for the job will depend on the degree of protection needed and the durability required of the material, especially if it is to be used for a second, third or even fourth season. Price will reflect the quality, density or weight of the fabric and its re-usability. An economic 17gsm spun-bonded polypropylene fleece may cost between £40 and £55 for a 250m roll with a width of 1.5m, depending on volume purchased. A more durable knitted, polyethylene crop-net is likely to be in the region of £200 for roll 8m wide by 250m in length. And with the industrial textiles market remaining extremely competitive, margins for the manufacturers and suppliers are narrow, so discounts are slim.
Catering largely for the smaller grower, professional gardeners and amenity markets, Wiltshire-based Agralan does not go in for shipping lorry loads of fleece but is one of the few suppliers to offer a 30gsm spun-bonded fleece.
"Where the temperature drops significantly, we would recommend Envirofleece 30," advises Agralan managing director Alan Frost. "It protects down to -6 degsC and is also a good insulator for greenhouses. In that respect it is easier to handle than bubble wrap and you don't get condensation problems with it."
The 30gsm Envirofleece is suitable for use on bedding plants, containerised stock and fruit. In addition, Agralan supplies the more economic 17gsm fleece to encourage growth and for situations where less frost protection is required. Making fixing more rapid and secure, Envirofleece Plus has a 40cm strip of fleece bonded to each side to give double thickness and strengthen the edges, while for greater longevity, the company offers Enivrotect - made of woven polyethylene ribbons.
"Envirotect gives a similar degree of protection to the 17gsm fleece but it is much stronger and could last up to four seasons," says Frost. "It also has the advantage that you can see through it."
Where soil warming is required, Agralan suggests Permalay - a 60gsm fleece that increases soil temperature while also acting as a mulch to eliminate weed growth. Ideal for organic gardeners and growers, Permalay is black and as such warms the soil better than white mulch materials.
Thermogro, an 18gsm fleece from Growing Technologies, works like a duvet to maintain a temperate micro-climate and protect plants from frost, snow, hail, rain splash and insect pests. The fleece can be used all year round to give optimum protection, allowing for an earlier and maximised crop. Every roll is individually UV treated and, due to its construction, the fleece has a high tension tear resistance. Seams are sonically welded.
Gro Frost Protection fleece from LBS Horticulture is manufactured from spun-bonded polypropylene and comes in 17gsm and 30gsm grades - lightweight to gently protect but not crush the delicate shoots and new growth. The material will protect against light frosts while raising soil temperature by several degrees to promote earlier crops and increase yields. At the same time bird and game damage to crops can be reduced.
UV stabilised to withstand use throughout the season, Gro Frost Protection fleece has a high translucence with air and moisture permeability. The 17gsm grade is available in 50m rolls with widths of 1.5m, 3.2m and 2m. Rolls are 250m are additionally offered in widths of 8m and 10.5m. The more heavy-duty 30gsm frost fleece is available in 100m rolls and widths of 1.5m, 2m 3.2m, 6.4m and 9.6m.
Fleece graded at 18gsm is offered by JFC Monro. Sizes include 4m x 100m or rolls of 250m with widths of 2m, 4m, 8.5m and 12.75m.
Humberside-based Brinkman UK offers the range of Lutrasil Pro crop-cover fleece. Made in Germany by Freudenberg, the fleece comes in an economic 17gsm grade as well as 19gsm, 21gsm, 23gsm and 30gsm. Narrow widths and field widths are available, along with bespoke widths and lengths subject to lead time.
With good durability and resistance to tearing and high winds, Lutrasil Pro can be used to form a protective, climate barrier around any horticultural crop. The non-woven fabric comprises continuous fibres provide climate control and strength, affording balanced temperature and humidity distribution as well as protection against pests. Water retention in the cross section of the fabric is limited to minimise damage to the crop.
Grades 17gsm and 19gsm are also available in 'X' format - that's with reinforced edges to provide extra strength when the fabric is dug in or pegged down. Recently introduced, Lutrasil Pro19X is, according to Brinkman, already proving popular with fruit and vegetable growers.
Mulch films from BPI Visqueen have been developed to enhance crop growth. The polythene films warm the soil by retaining heat and so aiding crop growth; they also prevent weed growth by blocking out the sunlight. Furthermore, the barrier formed by the mulch film locks the moisture in and reduces evaporation. In fruit production, the mulch can help keep berries clean and dry.
Well known for its vast range of agrotextiles, Capatex recently stopped selling non-woven crop-fleeces and now concentrates on promoting the advantages of Hi-Grow knitted crop net when used either as an alternative to fleece or in conjunction with a fleece fabric.
"It's a knitted net which is much stronger and much more durable than fleece. It lasts five to seven years if it is looked after, whereas you are often lucky to get one year out of a fleece," explains Capatex managing director Peter Strauss. The knitted net can also be made in larger widths.
"The maximum width you can make a fleece is really 4m. If you want a wider fleece of 12m or 16m, you have to glue it or ultra-sonically weld it. That means there are potential weak spots," says Strauss. "However, our knitted fabric can be knitted or sewn in widths up to 24m - and it's much stronger and more durable."
Hi-Grow knitted crop covers also have good light penetration and allow rain to pass through without it sitting in puddles on top of the material. In addition to having some thermal properties, the fabric also acts as an anti-bird or pigeon net. It can also be used as a second layer over the top of a fleece cover, providing a double layer for extra protection and also helping lengthen the life of the fleece - but it does mean there are two layers to remove.
Hi-Grow netting is supplied in 250m rolls with widths of 2m, 4m or 8m. A 12m by 100m knitted crop net is also available.
Also made from UV-stabilised knitted polyethylene, CosyTex is available from XL Horticulture and offers a long-lasting durable solution to crop protection.
"We have customers still using CosyTex eight years after purchase," says XL Horticulture director Les Lane. "If you leave it outside it will last for four years before it starts to break down. When you are just putting it over a crop it lasts longer."
Size and strength
Size and strength are key areas where the knitted polyethylene gains over spun-bonded fleece fabrics. "It can be made in really big sheets," says Lane. "We do a 20m x 100m sheet which is not far off half an acre, yet if you put a person in each corner and one in the middle, the whole sheet can be lifted. You can pull on it hard because it's so strong, so it's easy to move." The biggest order XL has supplied was for CosyTex to cover 45 acres.
CosyTex weighs 35gsm. Unlike fleece, it does not go soft when it gets wet and it doesn't puddle. Instead, it allows the rain to go through and it allows moist air to come back out. It gives the same degree of frost protection as a 17gsm spun-bonded crop protection fleece but of course it costs more.
"You can buy fleece for 4p or 5p a square metre, but with CosyTex you are talking more around 30p - but you can use it for years and you don't have an annual disposal problem," says Lane.
The fabric can be used on a wide range of crops. Since it keeps out pests such as cabbage white, it is used on brassicas and recently XL sold CosyTex to a vineyard owner who grows red grapes. Lane comments: "You only need a few more day degrees to produce red wine."