This is the first time I've grown luffa gourds in at least 20 years. My
first try back in the late 80's resulted in not a single luffa fruit.

Well, it appears that exactly the same thing is happening again. I
planted the seeds on the 1st of June, so the plants are now at about the 90
day point. They are strong and vigorous, on a lattice, and get plenty of
light. The vines are about 12 to 15 feet long, and 6 or 7 plants survived
from about 20 that I planted.

They have LOADS of male flowers, but the few immature female fruits that I
have seen are very few. Although a few have grown in size a bit, they all
end up turning yellow, shriveling up, and either just staying there, or
falling off without flowering. It is almost as if the plants have decided
"we are only going to make male flowers".

The seed packet said 100 days to maturity, so I would have thought I'd
have some female fruits by now. From what I've read, the flowers are about
all male at first, with a mix of male and female at mid season, and mostly
female flowers towards the end.

Anyone have any ideas why this might be happening? I am at a different
location than I was when this happened over 20 years ago.