Several threads from this forum are talking about reducing light during summer time, especially for dends. I have a question on that: do you reduce the length or intensity of light? Naturally, the length of the day light increases in summer (I grow them outside on patio).

I got a couple of dends (Garnet Jewel, Jacqueline Thomas, Little Diamond) that I haven't had any success to bring them to bloom, so I am willing to try something different.