Very informative article - I love the seed companies that provide us with so much growing information!
Where I am we have just recently (on Feb. 8th) exited the "Persephone period" - the days when we have less than 10 hours of daylight. And considering we have had very few sunny days during that time this winter, it's no wonder people get depressed.
However, the way I understand this, 10 hours of daylight is enough for growth, but not for flowering.
