Light VS. Heat

A number of growers I know have done some field trials on the so called Persephone rule, the idea that crops won’t grow once daylight hours drop below 10. What they have found is that if crops are keep sufficiently warm — usually the low 40s or higher, even in low-light conditions — they will see moderate continued growth. So, while most guides and resources focus on the hours of light, it actually is a mixture of both that will determine if and how much wintertime growth your crops can achieve.