Approximately 10 years ago we were collaborating on some research  looking at spectral filter (polythene covers which change the light spectrum entering the structure) tunnel covers that would grow a better crop of shade loving ericaceous plants.

The trials were conducted on a nursery in the South West of Ireland, a beautiful climate for growing those species of plants. The normal film used at the time for that type of crop was milky white. Alongside the milky white we included a normal clear film,  our new (at that time) SteriLite and our also new SmartGreen. SteriLite was developed to control botrytis and mildew as well as aphids on a wide range of crops. SmartGreen was developed specifically to mimic the light spectrum on a forest floor. 

Looking at the 3 pictures you can clearly see that the roots on the plants grown under the  Clear, SteriLite and SmartGeen are mostly far superior to the root structures under the Milky White. The only exception is the variegated Pieris where the Clear is not as a good a root structure as the Milky White. But in any case they are better than Milky White under the SteriLite or SmartGreen.

Looking at the plant quality both the SteriLite and the SmartGreen produced a far superior plant than under the milky white.

That pointed out to us the flaw in using Milky White for growing under and we haven’t made any since then. It’s cooler for the staff to work under in the summer, but it doesn’t grow anything like as good a crop, and that is after all why we use Polytunnels.