Luffa requires a long growing season. If planted early enough in the year, a few fruits will form in the spring that ripen by fall. During the long hot days of summer, pollination is inhibited, but resumes with the shorter days of autumn. If you have a 10-12 month growing season, you'll get a bumper crop of luffas at the end of the year.
The showy yellow male flowers open one at a time on an elongating upright stem.