It's a cover up! The eco-friendly guide to early sowings

Plastic fleeces and cloches can help you get a head start in the vegetable garden at this time of year. But are there ways to protect your crops without making lots of plastic waste, asks RHS Chief Horticulturist Guy Barter

Why cover your crops?

I have found fleece to be invaluable for early crops. Covering newly-sown or planted crops with cloches or fleece in mid-spring advances crops by about two weeks compared to leaving them uncovered.

Covering with fleece also cuts down risk of carrot fly, cabbage root fly and other pests, and weather damage. Some frost damage is excluded, giving around 2°C of protection. However, this will only prevent damage from light spring frosts if you're using it to protect courgettes, sweetcorn and other tender crops. It is not all about temperature though, in Britain wind damage is as important as harm from cold.

Is plant protection sustainable?

Horticultural fleece is a single use plastic product made of polypropylene fibres melded to make sheets. It is true that there are some heavier grade products that are more durable than the standard 17g per square metre fleece. These are typically 25-30g per square metre – but even these don’t last more than 2 years at best and are significantly more expensive, although offering slightly more warmth than 17g fleece. They are just as susceptible to deer and fox damage, both found on my allotment. 

Fleece has replaced the perforated polythene originally used to advance spring crops – it is much easier to use, excludes pests and gives more frost protection.  Perforated polythene is still used by farmers even though it is a single-use material. It is very cheap and also horribly muddy to pick up after use.

As an alternative, a woven polythene material, offered under the name of ‘Envirotect’ amongst others is available that is pleasant to use and lasts at least five years. It can be rinsed to clean it. It is made of very soft polythene and claims to have similar properties to 17g fleece. I don’t think it is quite as good as 17g fleece, but it is not bad. It is a little more expensive than fleece but over five years it is competitive.

What about glass?

To eliminate plastics entirely, glass continuous cloches (rows of panes clipped together) can be used. They were very popular last century  and the metal clips can still be found. Unfortunately glass is expensive, heavy, brittle and a potential safety hazard.

Despite the many gaps between the glass panes they do an excellent job. This is because glass allows in warmth but prevents re-emitted heat from escaping. I used to have quite a lot of them, but stopped using them after I spotted burglars one night and summoned the Metropolitan Police. Their large boots did grievous damage to my cloches.

Although plastic cloches do a fair job and can last several years, they are relatively expensive. A cheaper version can be made using tunnels of corrugated clear roofing sheet held in place by the steel fencing pins used to hold up safety netting. I have had some of these, sourced from a local builders' merchant, for 15 years, still sound and very useful.

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The Royal Horticultural Society is the UK’s leading gardening charity. We aim to enrich everyone’s life through plants, and make the UK a greener and more beautiful place.