I know from personal experience that Ipomoea nil blooms readily if exposed to short days. I am finding that vines bloom in winter when grown indoors, sometimes when the plants are very short in length. I am trying Ipomoea purpurea this winter indoors and think the plants will also bloom. I read some information online from a Japanese source that if you expose seedling Ipomoea nil to long nights (complete darkness) for say 14 hours, 4 days or so in succession, then grow them out under normal light dark schedule in early summer, you can shorten the time to bloom by maybe a month. I've seen others in this forum have luck getting Ipomoea tricolor to bloom under short days of winter using natural sunlight though the window. It's all fun.
