"Alan Gould" wrote in message
...

[snip]

Polytunnel covers need to be of ultraviolet inhibiting [UVI/EVA]
polythene of which three grades are offered. We chose Politherm Plus
in
720g with anti fogging and high light transmission properties.

Why do polythene tunnel covers need to block UV radiation?
Surely the same plants, growing in the open thrive the full dose of UV
radiation?

Franz