i've kept one garden for almost 20 years. the soil is gradually improving. what am i doing wrong?
Blame it on the worms...
Whenever I grow a member of the gourd family for seed, I allow the mature fruits to cure for several additional weeks before opening them for seed (or until they start to rot). The seeds generally fatten up during that period. So I am just now beginning to collect seeds from the luffa, which I've never grown successfully until this year.
The good news: it appears the seed was able to mature.
The bad (or less than great) news: wow, is it hard to get those seeds out!

I had to cut through those tough fibers lengthwise to expose the seed cavities, and even then had to squeeze the seeds out from their surrounding cell walls.

Luffa "Joy"
The fresh seeds initially look much like hull-less pumpkin seeds, but will dry to black. Now that I've seen the membrane surrounding them, I might try to ferment them next time (this time I'll rub off the membrane, as I do with squash).
The mature gourds are more prone to rot than other cucurbits I've grown, so 2/4 of those let go for seed needed to be done now; the remaining 2 will be done when they too begin to brown. I will boil the sponges in vinegar water to clean them.
By far not the greatest yield of any gourd I've grown; but I am happy to finally find a luffa that succeeds at my latitude. The young fruits are sweet & slimy when cooked, similar to okra... good in soups or stir fried. Filipinos call it "patola", and use it in Misua, a somewhat slimy soup. The vines are really eye-catching in bloom (which DW really wanted to see). The large male flowers develop on long racemes that bloom over a long period. An interesting plant, but not for those with limited space.