Buttercup squash is a variety of Cucurbita maxima, or winter squash, native to parts of North America. About 10 to 20 pounds, this medium-sized fruit appears along several 24-inch tall trailing vines in early summer and takes approximately 100 days to fully ripen. When ripe, buttercup squash develop bi-colored dark green and grayish skin with sweet orange flesh inside. It is best to determine the ripeness of buttercup squash before harvesting them since they cease ripening once removed from the vine; however, they provide several signs of ripeness that are easy to recognize.
Examine the coloring of the buttercup squash. This is the easiest way to tell if it is ripe. Look for dark green skin with subtle creamy stripes around the base and a cap of grayish-green skin with dark stripes along the top. Avoid squash with pale yellowish patches at the base or top. This indicates the squash is still immature.
Inspect the vine where it attaches to the top of the squash to see if it is completely desiccated and yellow. Tug on the squash to test if it will easily detach from the vine, which is a sure sign of ripeness.
Rap the buttercup squash with your knuckle. Listen for a soft, hollow sound to tell you it is ripe rather than a dull thump, which means it has a few more days to go before full maturity.
Cut the buttercup squash in half with a sharp knife. Look at the flesh to make sure it is uniformly orange in color with no white areas. Pierce the flesh with the tip of the knife to make sure it is soft, not dense and hard. Smell the flesh to see if the odor is strong and sweet rather than weak and slightly sour, which means it is still green.