I have planted lots of Waltham Butternuts this year and am having some frustrations as well. I have a number of very good plants, which I started and transplanted in late May. I got fruit sets as early as the 4th of July on some. Those are near ripe and up to 6-7 lbs, I'd guess.

Getting the next round of fruits to set and take off has been a problem. I have a number of plants where 2 females will set on successive nodes at the same time. When they have been the initial fruits on the vine, they have usually both succeeded. However, when one fruit has taken off - say, the initial round in July, the other big flush I got in early August blossomed, set, and then most all of them shriveled. I did a lot of hand pollinating with those so that should not be the issue.

Should I be pinching off all but one of these subsequent female flowers before they open to give one the best chance? I had one really good plent that threw four females a couple of feet down from a growing fruit. They all had nice big initial fruit, then they all died back.

On the plants that are not doing so well, I'm getting a lot of females that shoot out yellowish right from the start and don't even open. A lot of those have been in the containers I'm trying, where, admittedly they dry out a bit more and haven't gotten the son and perhaps nutrients they need.

Also, after looking very healthy all year, the best plants have gotten a little yellowish and spotty, especially where the biggest fruits are ripening. Is that just normal senescence? The latter half of these vines still look pretty vigorous, and I am getting a third round of female fruits right now, which will hopefully do better than the group from 2 weeks ago. I am actually pinching off all but one female flowers in the same vicinity to see if that helps.

Here is a link that might be useful: Rooftop, earthbox, and in-ground butternut / acorn squash