This is a daily total of just 3.5 hours, as opposed to the average 5.3 hours, and is a drop of one third. No wonder our Cannas are suffering with light deprevation.
We are not talking about periods when the sun was hidden behind clouds, and a reasonable temperature was still enjoyed. We are talking here of direct sunlight, which is a combination of bright light and heat.
Sunlight is a key factor in the process of photosynthesis, which is a series of steps for the conversion of light energy from the sun into chemical energy by our Cannas. Its initial participating components are carbon dioxide and water; the energy source is light (electromagnetic radiation); and the end-products are oxygen and (energy-containing) carbohydrates, such as sucrose, glucose, which are formed into roots, stems, leaves and flowers, or into starch which is stored in the Canna rhizomes.
Now that we have completed another polytunnel, it may be that we can grow some of our collection indoors during next summer; we are naturually reluctant to do that because of the additional problems from red-spider mite and fungal diseases, but maybe they are the lesser of the evils!