I have not had luck ripening butternuts off the vine. The skin changes color a little but they still do not taste very good (not terrible but not great.)

You have nothing to lose by trying, though.

My experience is that if they've started to get tan in color, but still have faint green stripes, those green stripes will gradually disappear when harvested. Disappearance of the green stripes is my signal to harvest. I'm not sure that a warm sunny spot will make any difference.

I was wondering if off-the-vine ripening was just a matter of time or of sunlight. Allegedly it's both. If you bring it in doors and keep it out of the sun, it won't ripen. I can't say that's been my experience, but so it is said.

That makes me wonder. What other vegetables (as in the edible parts, not the leaves) require sunlight to ripen? If I wrapped a green tomato on the vine in tinfoil, would it get red?

Thank you all. And you're right Peter1142, I've nothing to lose. Luckily we've had temps in the upper 70's for the past week. All the squash is on the deck, under a roof, so it's warm and sunny. And perhaps the butternuts are riper than I'd feared. I was at Costco yesterday and they were selling cubed butternut squash in the cooler room. It's color was not much different from the one I cut open. And if the flavor doesn't develop, I've still lots of Hubbarb, Kabocha, and pumpkins.

I often have to pick a few while the green stripes are still visible, and they do ripen in the sun.

Sounds like you have your storage plan on the right track.

My rule is a minimum of two months in storage before eating. They develop their sugar during this time. No eating until November! It will be worth the wait.

I did a little research, and found that at least pumpkins will ripen quite nicely off the vine as long as they have started to turn orange. I understand that dry, warm heat is optimal for this purpose, though once ripe, storage is best in cool temperatures. Sunlight isn't necessary for ripening pumpkins, interestingly. Not clear how much of this pertains to other winter squash.

Also, I note from the PSU extension, that winter squash should not be exposed to temps much below 50F before harvest or during storage, as it results in "chilling injury" and greatly reduces storage time. Over-chilled squash are thus recommended to be sold first.

As far as I understand it, the sunlight isn't necessary for ripening on any of the squash. The reason butternut (and all moschata types) need sunlight is to cure the skin so that they will keep long enough to sweeten.
Thats why after harvesting I put all the butternut in the greenhouse for about a month. After, they get boxed up and stored in a dry 50-60 degree room for the winter sales.

As other people said above, if butternuts have turned tan but still have some green, they should ripen. It's the ones that are still overall greenish that usually won't make it.

Sounds like yours should be fine.

-Mark

Do pumpkins also get sweeter after a time in storage?

Johnnyseeds says that most winter squash gets sweeter with storage time, as carbohydrates break down into sugars. I understand that the process can be accelerated by keeping the squash warm for a few weeks after harvest, though that may cut down on the storage lifetime. Interestingly, the caratenoid (think vitamin A) content of butternuts also increases with storage time, so older squash are healthier as well as sweeter.

I have three Waltham butternut squash that are huge, almost two feet long, and still green after months and months. They just keep growing instead of starting to ripen. And now we are in danger of having frost. Is there any chance at all that they will ripen in a warm place if I harvest them before the frost? This is the first year I have grown Walthams and they are supposedly sweeter and more flavorful than other butternut varieties so I was really looking forward to eating them, but they just keep growing instead of ripening. My neighbors joke that I'll need a wheelbarrow to get them into the house because they are so huge.

You might have started your squash with seeds that were not pure Waltham butternut. I had that happen a few years ago. The squash that grew was still good to eat but it wasn't what I expected.