Hanging baskets above the main production benches is a common approach for increasing space use efficiency in a greenhouse. However the shadow cast by the baskets has the potential to negatively affect the growth and quality of the crops growing on the benches. Faust (et al., 2014) found that;
a) the amount of shading increased with the number of baskets used – but the effect was not directly proportional to the number of baskets. For example – hanging enough baskets that they covered 5% of the roof area blocked out 5% of the incoming light – but at the highest density of baskets tested – where they covered 60% of the roof area – there was only a 26% reduction in light levels recorded on the benches below the baskets.
b) adding plants (poinsettias) to the pots increased their potential to block incoming light – although again the degree of blockage was not directly proportional to the size of the pot+plant.
c) hanging baskets with green pots absorbed 30% more light than baskets with white pots. This suggest the potential for the crop growing on the benches to benefit from reflected/diffuse light that has passed through or reflected off the overhead canopy of hanging baskets.
d) having light pass through a canopy of hanging baskets reduced the Red : Far Red ratio of the light that reached the benches. This change in light quality has the potential to negatively impact crop quality – as it encourages lanky growth with few branches. The researchers however emphasis that the reduction in total amount of light reaching the benches would be expected to have a far greater potential to negatively impact crop growth than any change in the spectral characteristics of the light that occurred as it passed through the canopy of hanging baskets.
Source : Faust, Korczynski and Samarkoon (2014) HortTechnology 24: 369-373.