The three sisters planting specifies winter squash or pumpkin. Is it OK to use summer squash in some of the planting, such as yellow or zucchini? In zone 8 or 9, the winter squashes do not fare well over summer and are usually planted in the late fall.
Traditionally, hard squash is used, but a summer squash will work as well. You just need the big leaves for shading the roots.
Do squash seeds need to be allowed to dry before they are planted again? I was given some winter squash to eat and like them so much that I would like to grow them for myself.
While it's not always necessary, I prefer to dry out the seeds prior to planting. This article will help with growing vegetables from seeds: https://www.gardeningknowhow.com/edible/vegetables/vgen/growing-vegetables-with-seeds.htm
When should I fertilize my winter squash or how often?
Assuming you added fertilizer when you first planted your squash, you should side dress with additional fertilizer/compost mid season. Winter squash are not heavy feeders, so one side dressing should be enough.
What are the watering needs of winter squash? I have a high clay content to my soil. Not sure whether I'm over or under watering mine.
They need 2-4" of water a week, including the rainfall. With clay soil, you may need to water a bit less or more frequently to avoid developing water logged soil, which will harm the plants.
Why do most of my winter squash rot just after the flowers die?
It sounds like a pollination problem, though it could also be attributed to blossom end rot. These articles will help:
https://www.gardeningknowhow.com/garden-how-to/beneficial/insect-pollination-process.htm
https://www.gardeningknowhow.com/edible/vegetables/squash/squash-fruit-falling-off-the-plant.htm
https://www.gardeningknowhow.com/edible/vegetables/squash/pollinate-squash-by-hand.htm
If they have blossom end rot. This article will help:
https://www.gardeningknowhow.com/edible/vegetables/squash/squash-blossom-end-rot-causes-and-treatment.htm
How long does it take winter squash that has been picked to get ripe?
This article can help you with that:
https://www.gardeningknowhow.com/edible/vegetables/squash/when-to-harvest-squash-best-time-to-pick-winter-or-summer-squash.htm
I have several 'winter' squash plants, and last night they were frosted. I am wondering when the squash will be ready. I have butternut and acorn varieties.
These articles can help you with that: https://www.gardeningknowhow.com/edible/vegetables/squash/when-to-harvest-squash-best-time-to-pick-winter-or-summer-squash.htm
https://www.gardeningknowhow.com/edible/vegetables/squash/ripening-green-unripe-squash.htm