Ripe butternut squash is creamy, sweet and nutty, perfect for pureeing and roasting. Unripened squash is bland, hard and not useful for much. The butternut squash's hard, protective shell makes determining the quality of the flesh inside tricky, but a few simple clues can help you gauge whether your squash will be delicious or a dud.
Look at the Squash
Visual clues can tell you a lot about the ripeness of a particular butternut squash. It should be beige all over, the darker the shade, the better. It should have no green patches. The skin should be mat, not shiny, and free of cuts and blemishes.
Feel the Squash
The weight of a squash can also give indications about its ripeness. It should feel heavy for its size. If you have many squash to choose from, look for the least ripe, greenest one and pick it up. Compare the weight of the squash you're considering to the weight of the less ripe squash.
Finally, try gently tapping the squash with your knuckles. You'll hear a hollow sound if it's ripe.