Shaped like their namesake, acorn squash are classified as a winter squash which, in earlier times, meant vegetables that were good keepers, typically those that would keep until December. Winter squash grow on vines and are harvested when fully mature, which takes 3 months or more, usually when cool fall weather arrives. Most can be stored for months in a cool basement. Acorn squash, however, are one of the most perishable winter squashes; they last only a few weeks in storage.
Squash is native to the Americas and is thought to be one of the first foods cultivated by Native Americans. Along with beans and corn, squash are part of the Indian triad of most important food staples. Acorn squash weigh an average of 1 to 3 pounds and usually are between 4 and 7 inches long; if you buy larger squash you risk dry, stringy flesh. Look for squash that feel heavy for their size and have no soft spots, sunken or moldy areas, cuts or punctures. Most acorn squash are dark green with orange splotches, but new varieties may be golden yellow, white or variegated. Skin should be smooth, dull and hard. Shiny skin indicates that either the squash was picked before it matured or that it has been waxed. A tender rind also indicates immaturity and, while orange splotches on a green squash are expected, too much orange could suggest that the squash is overripe, and therefore its flesh will be dry and stringy.
Use acorn squash within 2 weeks of purchase. After cooking, they can be stored in the refrigerator for up to 4 days.